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  • The effect of vibration and cutting zone temperature on surface roughness and tool wear in eco-friendly MQL turning of AISI D2
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-16
    Onur Özbek; Hamit Saruhan

    Today, developments in technology have gained momentum more than ever, and the need for efficiency in production as well as in the ecological domain has increased significantly. Studies examining dry machining and coolant removal have been superseded by those presenting new cooling and lubrication techniques. The effects on surface roughness directly related to final product quality are being investigated in terms of tool life and employee health. This has resulted in more frequent use of the eco-friendly minimum quantity lubrication (MQL) technique, which has now become a major competitor to dry and coolant machining. In this study, AISI D2 cold work tool steel, a material widely used in the mold industry, was used as the workpiece. Tests were carried out under dry and MQL conditions and the temperature, cutting tool vibration amplitude, tool wear, surface roughness and tool life were evaluated. The experiments were carried out using two different cutting tool coating types (CVD-chemical vapor deposition and PVD-physical vapor deposition) and three different cutting speeds (60, 90 and 120 m/min) at a constant cutting depth (1 mm) and feed rate (0.09 mm/rev). Results revealed that tool wear, cutting temperature and cutting tool vibration amplitude were lower by 23, 25, and 45%, respectively, compared to dry cutting. Because of these improvements, the surface roughness of the workpiece was improved by 89% and tool life was increased by up to 267%.

    更新日期:2020-01-17
  • Phase transformation and mechanical properties of B4C/Al composites
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-16
    Liu Zhang; Guopu Shi; Kun Xu; Wu Hao; Qinggang Li; Wu Junyan; Zhi Wang

    Lamellar constituted with 5, 15, 25 vol.% B4C/Al composites and homogeneous (namely 5, 15, 25 vol.% B4C/Al) composites were fabricated at sintering temperature 680 °C, sintering pressure 30 MPa, and heat preservation period 90 min via vacuum hot-pressing sintering. Another sample constituted with the raw materials of Al sheet and B4C powders has been prepared by the same sintering process to discuss the interface reaction of Al and B4C. In-situ XRD of B4C/Al mixed powders illustrated that the reaction products between Al and B4C were AlB2, AlB12, Al3BC. EDS and EPMA tests have proved that there was an element diffusion existing at the interface of B4C and Al. After sintering, new generation phases AlB12, Al3BC have been detected by SAED analysis of TEM, additionally, the inner microstructure of the lamellar B4C/Al composites was also observed. The results of mechanical properties showed that the lamellar B4C/Al composites possessed the optimal performance of Vicker hardness 116.23 ± 5.25 Hv, bending strength 780.45 ± 12.35 MPa and fracture toughness 12.21 ± 0.23 MPa∙m1/2, which was better than these of homogeneous B4C/Al composites.

    更新日期:2020-01-17
  • MgSO4 carbothermic reductive decomposition to produce a highly reactive MgO powder
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-16
    Bruno Souza; Rodrigo Souza; Iranildes Santos; Eduardo Brocchi

    Magnesium sulphate is commonly present in industrial wastes due to Mg’s presence in the structure of various minerals and the fact that sulphuric acid leaching is widely used. MgO appears as a possible pH neutralizing agent that can be obtained by decomposition of MgSO4. However, at 1500 K, the temperature where this decomposition occurs, the oxide formed cannot be used for this purpose. The thermodynamic study suggests that in the presence of reducing agents, such as carbon, decreasing the decomposition temperature makes the formed oxide viable for this use. The objective of the work is an evaluation of the behaviour of the reaction system constituted by MgSO4 and charcoal. The study also contemplates the obtained materials characterization to verify the MgO formation and evaluating how the properties of the material are suitable for its use as a pH regulator. Thus, in addition to the scanning and X-ray diffraction electron microscopy techniques, the quantification of the reactivity of the product in acid solutions is also expected. The analysis performed with the variables of excess reducing agent and temperature showed that temperature is the variable that most influences the decomposition of MgSO4. The experiments at 1173 K and 20, 25 and 30 min were the ones that indicated the best experimental results of conversion, reaching a conversion close to 100%. The characterization analysis, in XRD and SEM/EDS, indicated that MgO was formed at the end of the reaction. Reactivity test indicates that the obtained MgO can be used as a pH regulator.

    更新日期:2020-01-17
  • Dynamic and static softening behavior of a titanium added ultra-low carbon steel during hot and warm deformation
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-15
    Jônatas Venancio Barbosa; Túlio Magno Füzessy de Melo; Dagoberto Brandão Santos

    In this work, the mechanical and metallurgical behavior of titanium added ultra-low carbon (ULC-Ti) steel under hot and warm working conditions was studied by means of dilatometer compression tests. Double compression schedules were performed at temperatures between 700 °C and 1000 °C, inter-pass times of 0,5−100 s, and deformations of 0.5 and 0.3 in the first and second stages, respectively, with strain rate of 1 s−1. The analysis of the flow curves obtained allowed the evaluation of the softening characteristics of the steel. The softening and microstructure features indicate different restoration mechanisms depending of the temperature range. Static recrystallization with rapid microstructure restoration is observed at temperatures within the austenitic and intercritical region. Strain induced boundary motion and recovery mechanisms apparently control the restoration process in the ferrite region. In general, flow stress curves showed dynamic recovery behavior. Only the deformation in the intercritical region produced a peak in the flow stress curves. Isothermal holding tests associated with single hit compression indicated the presence of dynamic strain induced transformation, accelerating the softening kinetics at the intercritical region.

    更新日期:2020-01-15
  • Preparation of nanoporous CoCr alloy by dealloying CrCoNi medium entropy alloys
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-15
    Longfei Zeng; Chaoping You; Xufeng Cai; Chunming Wang; Xuehui Zhang; Tongxiang Liang

    High/Medium entropy alloys (H/MEAs) represent a new strategy for the design of materials with properties superior to those of conventional alloys. Here, we show a new field of application where the uniform mixtures of multiple principal elements in H/MEAs is utilized to create new type nanoporous alloys by dealloying. By using equiatomic CrCoNi MEAs as a proto-type system, we developed three-dimensional bi-continuous open nanoporous CoCr alloys composed of single-phase solid-solution with equiatomic ratios by liquid-metal dealloying methods. The morphology and size of ligaments and pores could be tailored by controlling dealloying time. Structural evolution of the nanoporous CoCr alloy during dealloying can be well described by surface smoothening and ligament pinch-off mediated coarsening process. This study opens up a new promising pathway for development of new type nanoporous alloys-nanoporous high entropy alloys, which are expected to have unprecedented structural and functional properties due to a unique synergistic combination of nanoporous structure and high-entropy effect.

    更新日期:2020-01-15
  • Hot deformation behaviour of 40CrNi steel and evaluation of different processing map construction methods
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-15
    Haitao Zhao; Jianjun Qi; Ru Su; Hongqi Zhang; Hongwei Chen; Lijuan Bai; Chengming Wang

    40CrNi steel is a low alloy steel with medium hardenability and has been widely used in the manufacturing of crankshafts, wind turbine forgings, etc. As forging is usually involved in the manufacturing of these components, optimization of the hot deformation process of 40CrNi steel is quite critical. Towards this, the prediction of flow stress and the determination of optimal processing parameter windows are of great importance. In this research, isothermal uniaxial hot compression tests were carried out for 40CrNi steel with true strain rates of 0.01, 0.1, 1, 10 and 30 s−1 and temperatures of 850–1200 °C. Both the strain compensated hyperbolic sine constitutive equation and the modified Johnson-Cook model were adopted to predict the flow stress curves, with average absolute relative errors of 0.034 and 0.061, respectively. Processing maps of the tested steel were constructed to determine the optimal deformation parameter windows, and the characteristics of the prior austenite microstructure generally correspond very well to the processing map established. Furthermore, different processing map construction methods were compared and it was found that power-dissipation efficiency maps strongly rely on the σ- ε˙ relationship. Assuming a certain type of constitutive equations leads to monotonic efficiency value patterns. Calculation methods based on experimental results are helpful to reflect the meaningful information carried by the experimental σ- ε˙ relationships.

    更新日期:2020-01-15
  • Practical examination of the welding residual stress in view of low-carbon steel welds
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-14
    Hsuan-Han Lai; Weite Wu

    The practical measurement of a welded workpiece is now feasible due to the improvement in the measuring instruments. There is a discrepancy between the theoretical and the measured welding stress profiles. In this study, stress analysis is performed on three low-carbon steel welds to investigate the reason behind the M-shaped stress profile. The welding residual stresses obtained from two different instruments show the same trend. A local high stress position is located in the tempered zone of the welding heat-affected zone. The solidification shrinkage leads to the compression of the un-melted metal near the fusion boundary and causes the discontinuous stress profile, resulting in the local high stress position in the heat-affected zone.

    更新日期:2020-01-14
  • Recovering metallic Pb directly from lead smelting dust by NaOH-carbon roasting process
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-14
    Jingxin Liu; Simian Huang; Kai Chen; Jinping Li; Teng Wang; Meng Mei

    Systematic chemical and mineralogical analyses were conducted for the dust generated in the Shuikoushan (SKS) lead smelting process, based on the results, an alternative strategy of direct metallic Pb recovery was proposed using NaOH⿿carbon roasting process. The reduction thermodynamics of PbSO4 was discussed, and the influencing parameters, including NaOH/dust mass ratio, carbon/dust mass ratio, roasting temperature and roasting time, were investigated systematically by experiments. The results indicated that increasing in the operation conditions was beneficial for the improved Pb recovery rate, and the reaction mechanism in this study was presumed as PbSO4⿿⿯C⿯PbS⿿⿯NaOH⿯Pb. The optimal conditions were determined as NaOH/dust mass ratio of 1.0, carbon/dust mass ratio of 0.2, roasting temperature of 650⿯°C and roasting time of 180⿯min. Under these conditions, 87.33% of Pb in the dust was directly recovered as metal pellets, gathering 96.48% of Bi, and 97.06% of As was converted into the alkali solution, while Zn and Cd were retained in the leaching residue. This process is clean and environmentally friendly for recovery of secondary resources bearing high content of PbSO4.

    更新日期:2020-01-14
  • Fungal degradation of reprocessed PP/PBAT/thermoplastic starch blends
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-13
    Thainá Araújo de Oliveira; Renata Barbosa; Avilnete B.S. Mesquita; Josie H.L. Ferreira; Laura Hecker de Carvalho; Tatianny Soares Alves

    It is well known that the inadequate disposal of polymeric materials causes significant environmental problems. Recycling and the use of biodegradable polymers are among the methods used to minimize these problems. However, the low mechanical performance of the majority of biodegradable polymers hinders the direct substitution of synthetic polymers, such as polyethylene (PE), polypropylene (PP) and polystyrene (PS), by biodegradable ones. Blending synthetic and biodegradable polymers is a way to develop recyclable biodegradable products with a good set of mechanical properties. Therefore, in this work we investigate the influence of extrusion cycles on the degradation of a polypropylene/poly (butylene adipate-co-terephthalate)/thermoplastic starch blend before and after inoculation with Aspergillus sp. and Penicillium sp. fungi degradaded for 30 days. The samples were exposed to the fungi and their mass loss, chemical structure, hydrophilicity, and morphology were observed as a function of inoculation time and processing cycles. Our results indicate that thermo-mechanical degradation favors the deposition of fungi in the samples and enables changes in film morphology and hydrophilicity.

    更新日期:2020-01-13
  • A novel method to determine full-range hardening curve for metal bar using hyperbolic shaped compression specimen
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-11
    Junfu Chen; Zhiping Guan; Jingsheng Xing; Dan Gao; Mingwen Ren

    In the determination of full-range hardening curve with compression test, the influence of friction and the corresponding stress correction have always been an enormous challenge. In this study, a hyperbolic shaped specimen is designed to conduct compression test for the determination of hardening curve in large range of strains without the effect of friction. The associated stress correction method is firstly derived by performing a series of finite element simulations of compression tests using the proposed specimen with the hardening curves composed with different combinations of initial yield stresses and strain hardening exponents. Finally, the hardening curves of mild steel Q420 obtained from the compression test using the proposed specimen are implemented in the simulation and verified with experimental data. The results show that the hyperbolic shaped compression specimen can not only remove the undesirable effect of friction but also determine the hardening curve in large range of strains. The established stress correction method for the hyperbolic shaped compression specimen is solely dependent on the strain hardening exponent, which can provide accurate hardening curve merely based on the experimental measurement of load vs. displacement curve and radius of middle cross section. Moreover, the hyperbolic shaped compression specimen provides a feasible approach to determine the strain hardening exponent of material.

    更新日期:2020-01-13
  • Effect of weld heat input on corrosion of dissimilar welded pipeline steels under simulated coating disbondment protected by cathodic protection
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-10
    R. Ashari; A. Eslami; M. Shamanian; S. Asghari

    Dissimilar welding is extensively used for oil and gas pipelines for new installations or repairs. Despite applying cathodic protection (CP) and coatings, corrosion and cracking can occur, usually on external surface of pipelines under coating disbondments close to weld lines. In this study, corrosion of dissimilar welded X-42 and grade B pipelines, under a simulated coating disbondment, is investigated. Welding was performed using shielded metal arc welding (SMAW) process. In order to simulate a coating disbondment, a corrosion cell containing 10 coupons was utilized. Coupons were exposed to a simulated soil solution purged with 5%CO2–95%N2 to maintain an anaerobic environment. CP potential of −870 mVSCE was applied to the open mouth of the disbondment. Results showed that by decreasing weld heat input from 0.74 to 0.61 kJ/mm, corrosion rate at the weld line increased. This was explained by formation of phases with higher corrosion rates (e.g. Widmanstatten and acicular ferrite). It was also observed that the corrosion rate at the weld line was higher than that at the heat affected zone (HAZ), followed by the base metals. The higher corrosion rate at the weld line and HAZ was explained by formation of acicular ferrite and secondary phases during the welding process. It was also observed that for similar heat inputs, the corrosion rate of dissimilar welded X-42 and grade B was higher than that of similar welded samples. This was possibly due to the minor galvanic effect between X-42 and the grade B pipeline steel.

    更新日期:2020-01-11
  • Microstructure and tribological property of CoCrFeMoNi High entropy alloy treated by ion sulfurization
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-10
    Gang Cui; Bin Han; Ying Yang; Yong Wang; Hu Chunyang

    The microstructures and tribological properties of CoCrFeMoNi high entropy alloy (HEA) before and after sulfurization were compared and discussed in the present study. The results showed that the CoCrFeMoNi HEA was mainly composed of FCC solid solution. After being sulfurized at 260℃ for 2 h, the FeS/MoS2 multisulfides solid lubricant films with a thickness of approximately 5.0 μm were successfully fabricated and well combined with the HEA. The stable friction coefficients and weight losses of the sulfurized HEA (0.15 and 4.25 mg) were decreased obviously than the original HEA (0.47 and 15.1 mg). At the beginning of the friction, the friction coefficient of the sulfurized HEA was easier to reach into stable stage. Because of the synergistic work of FeS and MoS2 lubricant phases, the sulfides boundary lubricant films were formed in the later stage of friction under the wearing condition, which could help the friction system work for longer time under lower friction coefficient.

    更新日期:2020-01-11
  • Improving the comprehensive mechanical property of the rheo-extruded Al-Fe alloy by severe rolling deformation
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-10
    Jiqiang Chen; Chao Liu; Renguo Guan; Feng Wen; Qiongyu Zhou; Hongjin Zhao

    Al-3Fe alloy was prepared by the method of continuous rheo-extrusion, and the effect of rolling deformation on the microstructure and the property of the rheo-extruded Al-3Fe alloy was studied by means of scanning electron microscope (SEM), transmission electron microscopy (TEM) and tensile test. The rheo-extruded pure Al was also prepared for comparison. The results showed that the rolling deformation could further refine the grain size of the rheo-extruded Al-Fe alloy, and reduce the size of the Al-Fe phase. Due to the present of nanosized and sub-micron sized Al3Fe phase, the strength of rheo-extruded Al-Fe alloy is significantly higher than that of rheo-extruded pure Al, and this advantage has been maintained during subsequently rolling deformation. Moreover, the strength and the elongation are simultaneously increased when the rolling reduction exceeds 60% for Al-Fe alloy and pure Al. Both of Al-Fe alloy and pure Al have the best comprehensive mechanical property when the rolling reduction reaches 90%. The main contribution is attributed to the grain refinement and the formation of high fraction substructure.

    更新日期:2020-01-11
  • Improved beneficiation of nickel and iron from a low-grade saprolite laterite by addition of limonitic laterite ore and CaCO3
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-10
    Hongyu Tian; Jian Pan; Deqing Zhu; Congcong Yang; Zhengqi Guo; Yuxiao Xue

    As is well known, the process of direct reduction and magnetic separation is effective route to deal with low-grade saprolite laterite, but generally limited by the reduction of nickel (iron)-bearing minerals and growth of Fe-Ni alloy particles in the reduction process, causing the low recovery of nickel and iron. To improve beneficiation of nickel and iron from low-grade saprolite laterite with 1.29 wt.%Ni and 16.31 wt.%Fe, co-reduction with limonitic laterite ore and basicity optimization were adopted as strengthening measures in this paper with better economic efficiency than before. The enhancing mechanism was investigated via the thermodynamics analysis and mineralogical study. The phase transformation and growth behaviors of metallic alloy particles during reduction process were revealed as well. The results indicated that co-reduction with limonitic laterite ore is capable of promoting phase transformation from Ni2SiO4 in saprolite laterite to NiFe2O4. CaCO3 can not only destroy the structure of magnesium silicate to release nickel(iron)-bearing phase, but also enhance the reduction of Fe2SiO4 to form efficiently iron-based eutectoid with nickel and liquid phases to accelerate the growth of Fe-Ni fine particles larger than 40 μm. A superior crude alloy was obtained with 5.11 wt.%Ni and 82.15 wt.%Fe with corresponding recovery rates of 91.89% and 85.15% respectively.

    更新日期:2020-01-11
  • Evaluation of corrosion inhibition performance of phosphorus polymer for carbon steel in [1 M] HCl: Computational studies (DFT, MC and MD simulations)
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-10
    Rachid Hsissou; Said Abbout; Rajaa Seghiri; Malak Rehioui; Avni Berisha; Hamid Erramli; Mohammed Assouag; Ahmed Elharfi

    Pentaglycidyl ether pentabisphenol A of phosphorus (PGEPBAP) phosphorus polymer was investigated as corrosion inhibition for carbon steel in aggressive solution using potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), weight loss (WL), scanning electron microscope (SEM), density functional theory (DFT), electrostatic potential (ESP), radial distribution function (RDF), molecular dynamics (MD) and Monte Carlo (MC) simulations. The higher inhibition efficiencies for PDP, EIS and WL studies at 10−3 M concentration of PGEPBA phosphorus polymer are 94.18 %, 91.79 % and 91.3 %, respectively. ΔEcorr (23.7 mV) value of PGEPBAP phosphorus polymer is lower than 85 mV has been assigned to mixed type inhibitor. PGEPBAP formed protective film on carbon steel surface by adsorption according to Langmuir adsorption isotherm. SEM morphology suggested that PGEPBAP could effectively block acid attack by chemisorption on metal surface. To evaluate the polymer inhibitor and potential mechanism were especially realized DFT, ESP, RDF, MD and MC simulations.

    更新日期:2020-01-11
  • Green hydrothermal synthesis of high quality single and few layers graphene sheets by bread waste as precursor
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-10
    Mokhtar Panahi-Kalamuei; Omid Amiri; Masoud Salavati-Niasari

    Graphene and its derivatives are ideal candidates for a variety of applications due to their distinctive optical, thermal, mechanical, and electronic properties, but its high price limits its application. Because of scalable graphene production method still stands as a serious barrier for its broad use. Here we develop a simple method to produce high quality single layer graphene with approximately 3 $/m2 in cost, while current price is about 56,000 $/m2. Food waste (bread waste) is used as starting material. Therefore, our introduced method also can serve as a valuable alternative to recycle food waste. Precursor concentration, pH and reaction temperature can create significant effects on the quality of final products. Single layer graphene sheet is achieved when concentration, reaction temperature and pH is used in 2 g/L, 180 °C and 7, respectively. Reaction is performed in ambient condition which is an advantage for scale up this method.

    更新日期:2020-01-11
  • Secondary spreading of acidified aerosols on the surface of Zn
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-10
    Miaoran Liu; Qi Yin; Yuwei Liu; Chen Pan; Chuan Wang; Zhenyao Wang

    Secondary spreading of acidified sodium chloride (NaCl) aerosol droplets on the surface of zinc have been studied. The in-situ observation of the secondary spreading, corrosion morphology, corrosion products under different position and volume loss are used to understand the secondary spreading of the acidified aerosol. The results reveal that the secondary spreading effect of NaCl aerosol droplet is more pronounced compared to the acidified aerosol droplets which are mainly embodied in larger spreading region and faster spreading rate. The difference of the secondary spreading effect is associated with acidification which inhibits the increase in the pH at the periphery. Furthermore, lower corrosion rate was observed for the acidified aerosol droplets due to smaller secondary spreading area (cathodic region). The main corrosion product in the center of NaCl aerosol droplet and the aerosol droplet acidified by HCl is Simonkolleite, while for the aerosol droplet acidified by H2SO4 which shows several different corrosion morphologies in the center, the main corrosion products are Gordaite, Simonkolleite and Zn4Cl2(OH)4SO4 ∙ 5H2O. The formation of protective corrosion products Gordaite that can inhibit the anodic reaction leads to the smallest spreading area and the lowest corrosion rate for the aerosol droplet acidified by H2SO4.

    更新日期:2020-01-11
  • Flow behavior and 3D processing map for hot deformation of Ti-2.7Cu alloy
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-09
    Xuan Zhou; Kelu Wang; Shiqiang Lu; Xin Li; Rui Feng; Mingjun Zhong

    The isothermal constant strain rate compression test of Ti-2.7Cu alloy was carried out by Gleeble-3500 thermomechanical simulator. The hot deformation behavior at temperature of 740–890 °C and strain rate of 0.001–10 s−1 was studied. The results show that the flow stress of the alloy is more sensitive to the deformation temperature and strain rate. The flow stress will decrease with the increase of deformation temperature, and increase with the increase of strain rate. The constitutive equation of Ti-2.7Cu is derived by using the Arrhenius hyperbolic sine function, and the activation energy at a strain of 0.4 is 412.32 kJ/mol. Based on the experimental data, the power dissipation efficiency and the instability parameter were investigated. Processing maps were established by superimposing the instability map and the power dissipation map. Through processing map prediction and microstructure observation, the unstable zones are mainly flow localization (740–750 °C /0.56 s−1–10 s−1) and mechanical instability (825 °C–890 °C /0.32 s−1–10 s−1), and the deformation mechanism of the stable zone is mainly dynamic recrystallization. It is found that the suitable deformation parameters of Ti-2.7Cu alloy are as follows: deformation temperature 780 °C–825 °C, strain rate 0.001 s−1–0.056 s−1.

    更新日期:2020-01-11
  • Evaluating compressive properties and morphology of expandable polyurethane foam for use in a synthetic paediatric spine
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-09
    Nor Amalina Muhayudin; Khairul Salleh Basaruddin; Fiona McEvoy; Anthony Tansey

    An expandable rigid PU foam can turns into complex shapes, with a shell like structure on the outside and honeycomb structure on the inside, which can be easily shaped to a vertebra form. The present study aims to determine whether expandable rigid polyurethane foam was an appropriate substitute for rigid block polyurethane foam to model the trabecular bone. Static compression tests were performed to determine compressive moduli and yield stresses on three polyurethane foam densities namely 0.16 g/cm3, 0.24 g/cm3 and 0.42 g/cm3. Morphology of the PU foams for all densities was also observed. The compressive modulus for 0.16 g/cm3 and 0.24 g/cm3 were found varied from 40 to 43 MPa and 83 to 92 MPa while yield stress ranged from 2.1 to 2.3 MPa and 3.4 to 4.8 MPa respectively. As for 0.42 g/cm3, the compressive modulus and yield stress varied from 240 to 256 MPa and 38 to 40 MPa. Based on these results, the compressive modulus and yield stress of 0.24 g/cm3 compared favourably with rigid block PU foam and human cadavers presented in the literatures. Hence, the findings of this study could potentially be used in developing a synthetic vertebral trabecular bone of paediatric spine for biomechanical testing.

    更新日期:2020-01-11
  • Surface modification of kapok fibers by cold plasma surface treatment
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-08
    Murilo J.P. Macedo; Giovanna S. Silva; Michelle C. Feitor; Thércio H.C. Costa; Edson N. Ito; José D.D. Melo

    This work evaluated the effects of cold plasma treatment on kapok fibers (Ceiba pentandra L.). Fourier-transform infrared (FTIR) spectra showed changes in characteristic absorption bands, indicating modification of the chemical composition of the fiber. Surface roughness, observed by field-emission gun scanning electron microscope (FEG-SEM), increased. Furthermore, the water uptake was significantly affected, the ability to uptake oil increased and a mechanism of reaction was suggested. The thermal behavior, analyzed by thermogravimetric analysis (TGA), was slightly altered and it was also shown that fiber surface was activated by the plasma treatment. Ultimately, cold plasma may prove as a feasible approach to improve fiber-matrix adhesion for the production of biodegradable polymer composites.

    更新日期:2020-01-09
  • Plastic strain-induced evolution of CSL boundaries at elevated temperature for Ni-base superalloy: experimental and phase-field perspective
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-08
    Xiaoqing Song; Liying Tang; Yongxin Wang; Rongcan Zhou; Jing Zhang; Zheng Chen

    Samples cut from a 700 ℃/322 MPa/9117 h creep-ruptured specimen as well as a non-tested sample were characterized by electron backscatter diffraction to investigate the evolution of low ∑ (∑≤29) coincident site lattice boundaries during strain at elevated temperature for Haynes 282 superalloy. Results show that the proportion of ∑3 boundaries, including ∑9 and ∑27 boundaries, decreases sharply with increasing strain. The two-mode phase-field crystal method is applied to simulate the dynamic evolution process of a ∑3 boundary. During deformation at ε´=5.62e-6, a twin embryo grows toward the initial ∑3 boundary with increasing strain and impinges onto it finally to form a ∑3-∑3-∑9 triple junction. In addition, part of the initial ∑3 boundary transforms into random grain boundary when the strain is large enough. Large numbers of dislocations are detected nearby ∑3 boundaries. They cause severe lattice rotations near ∑3 boundaries. In addition, some straight random boundaries can be found in strain zones only. Therefore, the transformation of ∑3 boundaries into random grain boundaries is the critical reason for the sharp decrease of ∑3 boundaries in strain zones.

    更新日期:2020-01-09
  • Analysis of copper and zinc alloy surface by exposure to alcohol aqueous solutions and sugarcane liquor
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-08
    Cláudio Faria Lopes Junior; Glauco Silva de Assis Machado; Patrícia Sousa Nilo Mendes; Priscila Sousa Nilo Mendes; José Augusto Oliveira Huguenin; Elivelton Alves Ferreira; Ladário da Silva

    Copper and zinc alloys have applications in products exposed to harsh environments. Usually, these products have upon their surface a thin film of oxides, whose properties may change due to the exposure to air or aqueous solutions at room temperatures. This work analyzed copper and zinc alloy surfaces exposed to aqueous solutions of alcohol and a sugarcane liquor using mainly spectroscopic ellipsometry and confocal microscopy at room temperature. Using ellipsometry, oxide thickness was measured, either native ones or grown ones on the substrate exposed to air, and finally, those grown with the used solutions. Confocal microscopy was used to analyze the topography of the samples and measure their surface roughness in all processes. Besides, scanning electron microscopy with energy dispersion spectroscopy verified the composition of the elements present in the alloy, obtaining 70% Cu and 30% Zn. Surface roughness and oxide thickness were monitored by 29 days when the surfaces were exposed to air. Average roughness Ra varied from 0.165 µm (day 1) to 0.222 µm (day 29). Oxide thickness ranged from 4.755 nm (day 1) to 11.192 (day 29) in the same time interval when surfaces were exposed to air at room temperature. Roughness and thickness were also measured when the surfaces were exposed to aqueous solutions of alcohol and a sugarcane liquor at 1.5 h, 8 h, 24 h, and 48 h of exposure. The greatest variation for both average roughness Ra (0.232 µm to 0.76 µm) and oxide thickness (32.774 nm–68.105 nm) was observed when the surfaces were exposed to sugarcane liquor.

    更新日期:2020-01-09
  • Improved sub-ppm acetone sensing properties of SnO2 nanowire-based sensor by attachment of Co3O4 nanoparticles
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-08
    Hongseok Kim; Zhicheng Cai; Sung-Pil Chang; Sunghoon Park

    Co3O4 nanoparticle-attached SnO2 nanowires are synthesized to fabricate highly sensitive acetone gas sensor by vapor-liquid-solid (VLS), sol-gel, and thermal annealing processes. To analyze enhanced acetone gas sensing responses, Co3O4 nanoparticles are attached SnO2 nanowires, and several samples are synthesized followed by the cycles of Co3O4 nanoparticle attachment process. The sensing response of Co3O4 nanoparticle-attached SnO2 nanowires, which are one time performed Co3O4 nanoparticle attachment process, is improved by 7 times compared with as-synthesized SnO2 nanowires when exposed to 50 ppm acetone gas. In particular, when exposed to 0.5 ppm acetone gas, as-synthesized SnO2 nanowires present an extremely low response — close to negligible. However, when Co3O4 nanoparticles are attached, the response is improved drastically. Furthermore, the sensing selectivity toward acetone gas is improved compared with its counterpart. This improved sensing property is derived from the increasing variation in the surface depletion area located in the p-n heterojunction.

    更新日期:2020-01-08
  • Development of a hydrometallurgical process for the recovery of pure alumina from black dross and synthesis of magnesium spinel
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-08
    Thi Thuy Nhi Nguyen; Si Jeong Song; Man Seung Lee

    In order to recover pure alumina and synthesize magnesium spinel from black dross, a hydrometallurgical process was developed. This process consisted of 1) NaOH leaching of the mechanically activated black dross, 2) removal of silicate(IV) from the leaching solution by adsorption followed by coagulation, 3) precipitation of aluminum hydroxide from the purified leaching solution, 4) synthesis of magnesium spinel. Continuous experiments on the above-mentioned steps at optimum conditions were performed. Magnesium spinel was synthesized at 1000 °C for 5 hs by the co-precipitation method. The purity of spinel was 99.99 % and its characteristics were analyzed by XRD and SEM. Mass balance of the whole process indicated that the recovery percentage of alumina from the black dross was only 34 % owing to low leaching percentage. Further work on the pretreatments of black dross to improve its dissolution behavior is needed.

    更新日期:2020-01-08
  • HZSM-5 zeolite supported boron-doped TiO2 for photocatalytic degradation of ofloxacin
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-08
    Haolun Li; Wenjie Zhang; Yuxuan Liu

    Boron-doped TiO2 was supported on HZSM-5 zeolite in a sol-gel route to prepare B-TiO2(x%)/HZSM-5 composites. The composites are composed of anatase TiO2 and HZSM-5 zeolite. The crystallite size of anatase TiO2 decreases after loading B-TiO2 on HZSM-5 zeolite. The SEM and TEM images of the composite show the dispersion of the B-TiO2 crystals on the external surface of HZSM-5. The bandgap energies of B-TiO2(x%)/HZSM-5 composites are approximately 3.2 eV. The N2 adsorption-desorption isotherms indicate that B-TiO2 is a mesoporous material and HZSM-5 zeolite is a microporous material. The mesoporous B-TiO2 layer is loaded on the external surface of the zeolite and does not enter into the inner micropores. The XPS results indicate the unchanged chemical environments of both titanium and oxygen in the supported B-TiO2. The B-TiO2(x%)/HZSM-5 composites have higher photocatalytic activity than the unsupported B-TiO2. The optimum B-TiO2 loading content is 20% in the composite, and 55.3% of the original ofloxacin molecules were degraded on the sample after 30 min of irradiation. Photocatalytic oxidation not only causes breaking up of the ofloxacin molecules, but also leads to decomposition of the major functional groups of the ofloxacin molecules.

    更新日期:2020-01-08
  • Effects of extrusion parameters and post-heat treatments on microstructures and mechanical properties of extrusion weld seams in 2195 Al-Li alloy profiles
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-08
    Xiao Xu; Guoqun Zhao; Shubin Yu; Yongxiao Wang; Xiaoxue Chen; Wendong Zhang

    To obtain profiles with sound weld seams, the effects of extrusion parameters and heat treatment on microstructures and mechanical properties of the weld seam were revealed. It was found that the high extrusion speed increases the mechanical properties and welding quality of the welding area. The micro-voids formed in low temperature and low extrusion speed could hinder the grains from growing through the welding interface during heat treatment, which caused weak bonding of the weld seam. Lots of strengthening phases precipitated during aging treatment, which leads to the disappearance of the softened welding area and the improvement of tensile strength. However, the fine grains of welding area translated to coarse grains quickly during solution treatment, and the precipitated phases coarsened and the precipitation free zone (PFZ) widened when the aging time is excessive, above reasons result in the layered fracture of welding area and poor elongation. Tensile strength and elongation were improved simultaneously because of the fine grain boundary precipitates, narrow PFZ and fine homogeneous T1 phases formed in under-aged (UA) treatment. The weld seam obtained by high extrusion speed shows a fine combination of ultimate tensile strength (UTS) and elongation after UA treatment.

    更新日期:2020-01-08
  • Microstructure characteristics and mechanical behaviour of a selective laser melted Inconel 718 alloy
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-08
    Liang Huang; Yan Cao; Gaohong Li; Yuanfei Wang

    In this study, an Inconel 718 alloy was prepared by selective laser melting (SLM) with a pre-alloyed powder, and the microstructure and mechanical behaviour of the fabricated parts were studied. First, the settled layer structure, composed of several interlaced "perlage" molten pools and molten channels, was captured by low-magnification optical microscopy (OM), and the formation mechanism was revealed by the Gaussian heat source distribution characteristics of the laser source used for the SLM fabrication. Second, high-magnification scanning electron microscopy (SEM) captured the different crystal structures in different fabricated positions; meanwhile, the "cross-border growth phenomenon" along the forming direction and the "growth and distribution characteristics of the crystal" in the radial direction (perpendicular to the forming direction) were also captured. By introducing the component super-cooling theory, the growth mechanism of crystal structures in different positions under a multi-dimensional temperature gradient heat conduction coupling mode is proposed. Finally, combined with transmission electron microscopy (TEM) and a mechanical properties test, it was found that the mechanical properties were between those of parts fabricated by casting and those by forging because the γ" phase and γ' phase were distributed in the crystal, while the carbide phase and Laves phase were distributed in the intercrystal region.

    更新日期:2020-01-08
  • On nitrogen diffusion during solution treatment in a high nitrogen austenitic stainless steel
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-07
    Rui Zhou; Derek O. Northwood; Cheng Liu

    The generation and microstructural characteristics of the surface layer formed during solution treatment at 1200 °C of a high nitrogen austenitic stainless steel, have been investigated using optical microscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS). Contrasting with a bulk microstructure of austenite and ferrite, a multi-layer surface structure is obtained, which consists of a white outer-surface layer which is ferrite and a grey subsurface layer with austenite. Formation of the multi-layer structure occurs through phase transformations between austenite and ferrite due to the various levels of nitrogen diffusion. With increasing solution treatment time, the thicknesses of both the surface and the subsurface layer increase. Hardness tests show that the microhardness increases from the surface layer, to the subsurface layer and then to the bulk. This is attributed to the combined effects of solid solution strengthening from nitrogen and the grain size of austenite or ferrite.

    更新日期:2020-01-07
  • Influence of curing time on the fire performance of solid reinforced concrete plates
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-07
    Gustavo Carniel Manica; Fabrício Longhi Bolina; Bernardo Fonseca Tutikian; Marcos Oliveira; Michael Anderson Moreira

    When reinforced concrete elements are subjected to high temperatures, such as in a fire, they are susceptible to physical and chemical changes that cause spalling, thereby undermining their performance under such conditions. It is known that the age and the internal moisture content of concrete are factors that contribute to this event, but the intensity of spalling is not yet a consensus. This study aimed to assess the influence of age and internal moisture on the performance of concrete walls at high temperatures. Therefore, 6 real-scale walls were built with dimensions of 3.15 × 3.00 m, with the same composition of concrete, for tests in a vertical furnace under the ISO 834 curve, for ages of 7, 14, 28, 56, 84 and 830 days. Moisture was measured as per the electrical resistivity of concrete. It was noted that walls with ages above 84 days showed no spalling whatsoever, due to the internal moisture of concrete. The most severe spalling took place at 14 days, thus evidencing that pore interconnectivity and hydrated cement crystallization can contribute as well.

    更新日期:2020-01-07
  • Effect of ultrasonication duration of polyvinyl alcohol (PVA) gel on characterizations of PVA film
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-07
    Hairul Abral; Arief Atmajaya; Melbi Mahardika; Fadli Hafizulhaq; Kadriadi; Dian Handayani; S.M. Sapuan; R.A. Ilyas

    Many works reported a PVA based film prepared using ultrasonication, however, information on the effect of this treatment on changes of PVA’s properties is still limited. The main objective of this work was to study the effect of ultrasonication duration on the properties of PVA film. The PVA gel was sonicated using a 360 W ultrasonic probe for 2.5, 5, 7.5 and 10 min. Ultrasonication duration for 7.5 min results in a significant effect (p ≤ 0.05) on an increase in tensile strength, but not on tensile modulus and strain at the break of the film. After this vibration duration, tensile strength increased by almost 29 %, strain at break decreased by 30 %, opacity decreased by 22 %, and water vapor permeability decreased by 11 %. On the other hand, moisture resistance decreased significantly (almost 12 %). The sonicated film underwent larger lattice strain and had higher crystal structure compared to non-sonicated film. This work informs that ultrasonication on PVA gel is a potential method to fulfil some properties of PVA film for food packaging material.

    更新日期:2020-01-07
  • Constitutive analysis and dynamic recrystallization behavior of as-cast 40CrNiMo alloy steel during isothermal compression
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-07
    Wei Wang; Rui Ma; Lianping Li; Ruixue Zhai; Shibo Ma; Huajun Yan; Shuangjie Zhang; Siyuan Gong

    Casting-forging combination forming process is an advanced manufacturing technique which is applicable to manufacture the parts with both complex shape and high performance. As a fundamental research of casting-forging combination forming process, as-cast 40CrNiMo alloy steel is obtained through vacuum casting by using metal mold. The isothermal compression tests of as-cast 40CrNiMo alloy steel are implemented on a Gleeble-3800 thermal simulation machine at deformation temperatures of 800, 900, 1000 and 1100 ℃, with strain rates of 0.001, 0.01, 0.1, 1 and 10 s−1. The results indicate that the true stress-strain curves present typical dynamic recovery type under low deformation temperature and high strain rate. With the increases of deformation temperature or the decreases of strain rate, the true stress-strain curves gradually transform to dynamic recrystallization type. The Arrhenius-type constitutive equation with Zener–Hollomon parameter is determined for constitutive analysis. The kinetic model and kinematic model of dynamic recrystallization are deduced to describe the dynamic recrystallization behavior.

    更新日期:2020-01-07
  • Evaluation of microstructure variation of TC11 alloy after electroshocking treatment
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-06
    Lechun Xie; Chang Liu; Yanli Song; Haojie Guo; Zhongqi Wang; Lin Hua; Liqiang Wang; Lai-Chang Zhang

    Electro-shocking treatment (EST) has been investigated as a pathway to optimise the microstructure and mechanical properties of titanium alloys. The thermal conditions introduced by EST resulted in a phase transformation from α to β. The fraction of β phase decreased from 25.27% to 19.47% after EST for 0.02 s, which was possibly caused by the recrystallization of α phase. The application of EST for 0.04 s resulted in an increase in volume fraction of the β phase to 26.95%. The energy introduced by EST resulted in changes to the direction and intensity of texture within the microstructure with the texture intensity of the α phase increasing from 4.94 to 8.52, and that of β both increased from 3.35 to 9.88 after 0.04 s EST.

    更新日期:2020-01-07
  • One-Pot Pulsed Laser Ablation route assisted copper oxide nanoparticles doped in PEO/PVP blend for the electrical conductivity enhancement
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-06
    A.A. Menazea

    Polyethylene Oxide (PEO)/Polyvinyl pyrrolidone (PVP)/Copper Oxide Nanoparticles (CuONPs) were synthesized by one-step Pulsed Laser Ablation of pure Copper plate immersed in PEO/PVP (70/30 wt.%) solution. PEO/PVP/CuONPs composite films were prepared using casting method. The role of copper nanoparticles on modifying PEO/PVP was demonstrated. The effect of different laser ablation times on the characterization of the prepared PEO/PVP/CuONPs composite films have been studied via XRD, UV–vis, PL, SEM, and Ac conductivity. XRD and SEM confirm the complexation between CuONPs and PEO/PVP matrix. The appearance of the characteristic absorption peak at 275 nm in UV–vis spectrum was attributed to the surface plasmon resonance (SPR) of CuONPs. The values of the direct and indirect optical band gap show a decreasing after doping PEO/PVP matrix by CuONPs. PL analysis confirmed that the existence of the CuO nanoparticles comprehensively reorders the delocalized n-electron system of PEO/PVP blend matrix. The behavior of dielectric constant and dielectric loss are progressively decreased as the frequency increased. The values of AC conductivity are increased as the laser ablation time increased. M' and M″ values are increased by increasing the concentration of CuONPs in the PEO/PVP blend matrix, which induces an increase in the ion conduction of the prepared samples.

    更新日期:2020-01-07
  • Poly-thiourea formaldehyde based anticorrosion marine coatings on Type 304 stainless steel
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-06
    Sehrish Kanwal; Naveed Zafar Ali; Rizwan Hussain; Zareen Akhter

    In the present study, hexamethylene diisocyanate (HMDI) encapsulated poly-thiourea formaldehyde (PTF) (10 wt%) coating was developed in an epoxy-polyamine matrix and their anticorrosion studies on Type SS304 stainless steel substrate have been conducted using electrochemistry techniques. The compact and hydrophobic shell wall of PTF proved to be a potent shell wall material for HMDI encapsulation. The effect of temperature and pH values was found to be decisive factor in the synthesis of microcapsules. The PTF microcapsules were synthesized in acidic condition with a pH value of 3. Over 90% of the core fraction is retained in water after 21 days immersion. However, core content decreased with increasing temperature. The capsules were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Electrochemical Impedance spectroscopy (EIS). Scanning electron microscopic analysis depicts the uniform morphology of coating with a particle size in the range of 1.08 μm–22.06 μm. The vibrational band at 2271 cm−1 attributed to NCO signal further endorses the successful encapsulation of HMDI into the PTF capsules. Electrochemical testing on steel specifies the appreciable anticorrosion performance of the synthesized poly thiourea formaldehyde (PTF) coating against artificial sea water.

    更新日期:2020-01-07
  • Microstructures and mechanical properties of stainless steel clad plate joint with diverse filler metals
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-06
    Chang’an Li; Guoliang Qin; Yuansheng Tang; Binggang Zhang; Sanbao Lin; Peihao Geng

    Thick stainless steel clad plate is used widely in the petroleum and petrochemical industries because of its low cost and good corrosion resistance. It is generally welded by the multilayer and multipass welding process with stainless steel filler metal matched with the clad layer. In this research, the base metal of stainless steel clad plates was filled with carbon steel filler metal, and the microstructures and mechanical properties of joints with diverse filler metals were analysed and compared. The results indicate that a local hardening zone (LHZ) forms in the weld filled with the filler metals of stainless steel and carbon steel because of the formation of martensite phase in the first layer of weld with filler metal of carbon steel. The microhardness value in LHZ reaches up to 425 HV1, which is significantly higher than that of the base metal. However, the tensile strength value of joints filled with carbon steel filler metal is equivalent to that of the joints with stainless steel filler metal. The results of the side bending test indicate that the LHZ protrudes from the weld, and the crack occurs near the LHZ if the area of the LHZ on the cross section of joint is larger than 17 % of that of the whole cross section of the joint. The studied results show that it is feasible to use carbon steel filler metal to fill the base metal of carbon steel in welding of stainless steel clad plate.

    更新日期:2020-01-07
  • Facile synthesis of supported AuNi and PtNi bimetallic nanomaterials and their enhanced catalytic properties
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-06
    Yingji Song; Yingzi Lin; Xuefeng Chu; Junhong Tang; Shaodan Xu

    Bimetallic materials are of great interest in scientific research and applications due to their unique chemical and physical properties. Here, we report a solid strategy to prepare AuNi bimetallic nanoparticles in large spherical cages of ordered mesoporous silica with uniform size distribution (AuxNi/mSiO2). The surface chemical composition and catalytic performance of BMNPs (Bimetallic Nanoparticles) are precisely varied via confined inter-particle hetero-atom migration. The AuxNi/mSiO2 catalyst displayed greatly improved catalytic performance and excellent stability in gas-phase oxidation of benzyl alcohol. Moreover, the strategy has been successfully extended to the synthesis of PtyNi/mSiO2, which performed higher activity and selectivity compared to the monometallic Pt catalyst in CO oxidation.

    更新日期:2020-01-07
  • Design and high-temperature tribological properties of CoCrW with rare earth fluoride composites
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-03
    GongJun Cui; Huiqiang Liu; Sai Li; Guijun Gao; Ziming Kou

    CoCrW matrix containing rare earth LaF3 self-lubricating composites were fabricated by using hot-pressing method. The microstructure, phases and high-temperature tribological properties of obtained composites were systematically studied. Friction and wear behaviors were evaluated by using ball-on-disc tribo-tester from RT (24 °C) to 1000 °C. Metal matrix consisted of two allotropes: ε (hcp) and γ (fcc). Mo had a solid solution strengthening effect and lubricating effect when it changed into compounds. Rare earth LaF3 and its compounds showed lubricating effect at elevated temperatures. The friction coefficients and wear resistance of reinforced composites were greatly enhanced with little hardness dropping. It was ascribed to the synergistic effect of in-situ formed and extra added solid lubricants (silver, LaCrO3, Ag2MoO4, AgF3 and metal oxides) as well as oxides film which changed the wear model of tribo-couples during sliding. The wear rate of CoCrW-10LaF3-8Mo-9Ag was about 10 times lower than those of reported Ni and ZrO2 matrix composites. The composites showed the slight abrasive wear and oxidative wear at elevated temperatures.

    更新日期:2020-01-04
  • Evaluation of tool wear, surface roughness/topography and chip morphology when machining of Ni-based alloy 625 under MQL, cryogenic cooling and CryoMQL
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-03
    Çağrı Vakkas Yıldırım; Turgay Kıvak; Murat Sarıkaya; Şenol Şirin

    Although nickel-based aerospace superalloys such as alloy 625 have superior properties including high-tensile and fatigue strength, corrosion resistance and good weldability, etc., its machinability is a difficult task which can be solved with alternative cooling/lubrication strategies. It is also important that these solution methods are sustainable. In order to facilitate the machinability of alloy 625 with sustainable techniques, we investigated the effect of minimum quantity lubrication (MQL), cryogenic cooling with liquid nitrogen (LN2) and hybrid-CryoMQL methods on tool wear behavior, cutting temperature, surface roughness/topography and chip morphology in a turning operation. The experiments were performed at three cutting speeds (50, 75 and 100 m/min), fixed cutting depth (0.5 mm) and feed rate (0.12 mm/rev). As a result, CryoMQL improved surface roughness (1.42 µm) by 24.82% compared to cryogenic cooling. The medium level of cutting speed (75 m/min) can be preferred for the lowest roughness value and lowest peak-to-valley height when turning of alloy 625. Further, tool wear is decreased by 50.67% and 79.60% by the use of MQL and CryoMQL compared with cryogenic machining. An interesting result that MQL is more effective than cryogenic machining in reducing cutting tool wear.

    更新日期:2020-01-04
  • Conceptual design of multi-operation outdoor flexural creep test rig using hybrid concurrent engineering approach
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-03
    M.R.M. Asyraf; M.R. Ishak; S.M. Sapuan; N. Yidris

    The hybridisation of conceptual design methods is presented in the development of multi-operations creep flexural test rig. The paper explains the integration of theory of inventive problem solving (TRIZ), Morphological chart, and Analytic Network Process (ANP) method to ensure the quality function is fulfilled with the essential requirements. The objective of this project is to produce and choose the best design concept for the product development depending on the product design specifications (PDS). In the early stage of product development, the TRIZ contradiction principles and 40 TRIZ inventive solutions were applied as the guidance tools. To refine the specification of the product design, the principle solution parameters were detailed systematically with the aid of morphological chart. In this article, four innovative conceptual designs of the multi-operations creep flexural test rig were produced and the selection process was conducted using ANP method to perform the multi-criteria decision making process in selecting the best concept design.

    更新日期:2020-01-04
  • Effect of graphene oxide coating on the ballistic performance of aramid fabric
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-03
    Anderson Oliveira da Silva; Ricardo Pondé Weber; Sérgio Neves Monteiro; Andreza Menezes Lima; Géssica Seara Faria; Wesley Oliveira da Silva; Suzane de Sant’ Ana Oliveira; Karollyne Gomes de Castro Monsores; Wagner Anacleto Pinheiro

    Twaron® brand aromatic polyamide, commonly known as aramid fabric, was reinforced with a solution of graphene oxide (GO) followed by a heat treatment at 120 °C. The objective was to improve the ballistic properties of the material by increasing the friction coefficient of the fibers in the fabric. The GO produced by the modified Hummers method was characterized by Fourier transform infrared and Raman spectroscopy as well as by scanning electron microscopy (SEM) and atomic force microscopy. Both the as-received fabric and fabric coated with one and two filtrations of GO were characterized by the above-mentioned technique in addition to optical microscopy (OM). All samples were subjected to ballistic tests with 9 mm ammunition. The energy absorbed by the materials was calculated from the values ​​of impact velocities and residual obtained by Doppler radar. The type of failure was characterized by means of SEM and OM visual analysis. The results show a better resistive force of the two filtrations GO coated fabric, up to 50%, when compared to the plain as-received fabric.

    更新日期:2020-01-04
  • The influence of Zn addition on microstructure of an Al-1.7 Cu-4.0 Li-0.4 Mg alloy
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-03
    Dan-yang Liu; Yun-long Ma; Jin-feng Li; Cheng Huang; Yang Wang; Zhi-xiu Wang; Rui-feng Zhang

    The tensile properties and corrosion behaviours of an ageing Al-1.7 Cu-4.0 Li- 0.4 Mg alloys (in at. %) with or without 0.3 Zn addition were investigated by detailed microstructure evolution using TEM and STEM. Herein, the Zn addition to the Al-1.7 Cu-4.0 Li- 0.4 Mg ageing alloy is determined as a convincing approach to optimising the strength-corrosion resistance balance. With Zn addition, the increasing quantity of T1 phase in grain led to the increase of the tensile property of the Al-1.7 Cu-4.0 Li- 0.4 Mg alloy. While the studied alloy with Zn addition possessed preferable corrosion resistance in respect of intergranular corrosion (IGC) depth reducing. Moreover, the emergence of Zn elements in the coarse phases at grain boundary (GB) may decrease the potential differences between the precipitates at GB and free precipitation zone (PFZ), which could increase corrosion resistance.

    更新日期:2020-01-04
  • Plastic flow behavior for machined surface material Ti-6Al-4V with rotary ultrasonic burnishing
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-02
    Jian Zhao; Zhanqiang Liu

    A hybrid machining technology with rotary ultrasonic roller burnishing process has been developed. There is no material removal when the machined surface is generated by the hybrid ultrasonic burnishing as comparing with other conventional cutting processes. The kinematic mechanism for plastic flow during surface generation in hybrid rotary ultrasonic burnishing Ti-6Al-4V with cylindrical roller tool was revealed in this paper. Firstly, the machining experiments were carried out for surface generation with hybrid rotary ultrasonic burnishing Ti-6Al-4V. Then, the experimental analysis was conducted and it showed that, there was little change in dimension of the rotary ultrasonic roller burnished workpiece compared to that of milled workpiece. Finally, a 3D finite element (FE) model was proposed to simulate the surface generation in hybrid rotary ultrasonic roller burnishing process. Three machining zones including pile-up deformation area, tensile deformation area, and compressive deformation area were selected for the analysis of the material plastic flow. It was found that the surface generated by rotary ultrasonic burnishing was mainly attributed to the plastic flow of material in these three deformation zones. The FE simulation results showed good agreements with the experimental ones. The proposed research results are helpful for the analysis and diagnosis of the surface generation in ultrasonic burnishing process.

    更新日期:2020-01-02
  • Hydrometallurgical separation of zinc and copper from waste brass ashes using solvent extraction with D2EHPA
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-02
    Júlia Mont’Alverne Martins; Alexandre Silva Guimarães; Achilles Junqueira Bourdot Dutra; Marcelo Borges Mansur

    A blend of brass ashes containing 48.0% of zinc and 16.6% of copper was processed through selective leaching with dilute H2SO4 and solvent extraction, using D2EHPA as the extracting agent in order to separate zinc and copper. Solvent extraction tests performed in bench and pilot scales were designed to evaluate the following operating parameters: time, pH, D2EHPA concentration, A/O ratio in the extraction step, and O/A ratio in the stripping step. Zinc present in the brass ashes was efficiently leached by H2SO4 (recovery of 91.9%), whereas only 8.6% of copper was leached, producing a liquor containing zinc (28.6 g/L), copper (1.5 g/L), calcium (0.45 g/L), iron (0.43 g/L), and chloride (0.22 g/L), as well as fluoride, lead, nickel and cadmium, at levels below 0.01 g/L. Zinc was selectively extracted over copper by solvent extraction with D2EHPA. A continuous solvent extraction run in pilot scale was carried out using 4 extraction stages (pH = 2, A/O ratio = 1) and 2 stripping stages (O/A ratio = 2), where 91.8% of zinc extraction and 96.9% of zinc stripping were achieved. Iron extraction efficiency reached 85.9%, thus illustrating the need for its prior removal if required. The fluorine extraction was 29.9%, as compared to 10.4% for chlorine, whose respective extractions are related to the presence of iron and zinc in the liquor, as evidenced by species speciation analysis. A copper concentrate containing 42.2% was obtained in the leaching step.

    更新日期:2020-01-02
  • The optimization and characterization of the recycling utilization of raffinate in the copper leaching process
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-02
    Long Wang; Shimin Song; Hanyu Gao; Ling Wang; Siyuan Yang; Cheng Liu

    The raffinate in the extraction process contains plenty of acid and metallic ions, the dispose of which causes the resource loss and environmental pollution. The present study proposed an innovative way to solve this problem by using raffinate as the leaching agent in the copper leaching process. The effects of significant leaching parameters were investigated and optimized using the central composite design (CCD) of response surface methodology (RSM). A maximum leaching efficiency of 96.74 % can be obtained under the 53.22 Kg/t of initial acidity, 2.54 h of leaching time and 5.95 of liquid/solid ratio. In addition, the comparative features of samples before and after leaching process were analyzed by using the X-ray diffraction (XRD), sieving test, scanning electron microscope (SEM) and adsorption-desorption isotherms. We found that the majority of copper components have been removed from copper ores, causing the reduction of size distributions. Specifically, the content of <38 μm after leaching was largely increased from 43.71% to 85.00%. It also led to the appearance of micro pores and cracks in the copper ores, so as to increase the specific surface area and the adsorption mean aperture, which were beneficial to the copper leaching process.

    更新日期:2020-01-02
  • Flow stress prediction using hyperbolic-sine Arrhenius constants optimised by simple generalised reduced gradient refinement
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2020-01-02
    Michael Oluwatosin Bodunrin

    The generalised reduced gradient refinement was applied to optimise the constitutive constants obtained from hyperbolic-sine Arrhenius equation when describing the flow stress of two titanium alloys subjected to hot compression testing. The results showed that correlation coefficients improved from 0.96 and 0.98 to 0.99, while the average absolute relative error and the root mean square error reduced by more than 30%. The simple generalised reduced gradient refinement can be used to improve the prediction of flow stress when hyperbolic-sine Arrhenius equation or other phenomenological and physical models are used for describing hot working behaviour of metals and alloys.

    更新日期:2020-01-02
  • Investigating the behaviour of hybrid fibre-reinforced reactive powder concrete beams after exposure to elevated temperatures
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2019-12-31
    Al-Attar Alyaa; Abdulrahman Mazin; Hamada Hussein; Tayeh Bassam

    This study investigated the structural behaviour of reinforced reactive powder concrete (RPC) beams under service load and fire exposure. The beams were composed of hybrid fibres (50% polypropylene fibres and 50% steel fibres) at different volume fractions relative to nonfibrous-reinforced RPC beams. The bottom and both sides of the beams which were simply supported and loaded with two-point loads were exposed to a controlled fire for 120 min in accordance with ASTM E 119 standard time–temperature curve. The midspan deflection was recorded every 5 min. The experiment also included loading tests on fire-damaged beams after cooling. The nonfibrous-reinforced RPC beams failed during the fire test after 38 min because of the spalling of the reinforcement cover which directly exposed the reinforcing steel to elevated temperatures. By contrast, the beams with hybrid fibres could resist failure during the entire test period. The rate of increase in deflection during fire exposure declined with an increase in hybrid fibre content. Increases in fibre volume fraction from 0.25% to 0.75% and 1.25% decreased the midspan deflection of the reinforced RPC beams by 33% and 36%, respectively. Adding hybrid fibres could considerably improve the residual stiffness of fire-damaged beams.

    更新日期:2020-01-01
  • Construction of microsphere-shaped ZnSe-AgZnInS and its charge transport property
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2019-12-31
    Fen Qiao; Zhenya Chen; Yi Xie; Baodong Mao; Dongqi Zhang; Huaqiang Chu; Qinglin Zhang

    The composite structure of ZnSe-AgZnInS microspheres was synthesized by two-step hydrothermal reaction, in which AgZnInS quantum dots (QDs) attached to the surface of ZnSe microspheres. Compared with pure ZnSe and AgZnInS QDs, the ZnSe-AgZnInS exhibited excellent photocatalytic activity for H2 generation under the illumination of a simulated sunlight. The results also showed that different mass ratios of AgZnInS QDs had a great influence on the photocatalytic performance of ZnSe-AgZnInS microspheres. When the AgZnInS QDs was 0.05 g/mol with the photocatalytic reduction time of 5 h, the H2 formation rate of ZnSe-AgZnInS reached the optimal value (343.108 μmolg−1 h−1), which was ∼20 times and more than 2 times higher than bare ZnSe and AgZnInS QDs, respectively. The related mechanism of photocatalytic hydrogen generation was investigated by suface photovoltage spectroscopy and transisent fluorescence. It was found that the efficient transport of photogenerated carriers at the interface between ZnSe and AgZnInS QDs contributed to the improvement of the photocatalytic performance of ZnSe-AgZnInS. This work provides further insights for the design and preparation of composite photocatalysts.

    更新日期:2019-12-31
  • Analysis of thermally stratified flow of Sutterby nanofluid with zero mass flux condition
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2019-12-31
    Saif-ur-Rehman; Nazir A.Mir; M. Farooq; M. Rizwan; F. Ahmad; S. Ahmad; B. Ahmad

    In this attempt, we scrutinize the effects of Sutterby nanoliquid flow deformed by a linearly stretchable sheet. Inclined magnetic field is included to explore the features of electrically conducting fluid. Thermal stratification phenomenon is implemented over a horizontal sheet to elaborate the features of heat transfer. Variable fluid feature is also accounted. Zero mass flux condition is incorporated along with Brownian diffusion and thermophoresis phenomenon Using the suitable transformations, the system of partial differential equations are transmuted into coupled system of ordinary differential equations. Approximate analytical solutions are computed via homotopic approach. Graphical behavior of applicable parameters on temperature, velocity, and concentration fields are illustrated and elaborated. Skin friction coefficient and Nusselt number are computed and analyzed. It is found that increase in fluid parameter declines the velocity field whereas temperature field rises for higher thermal conductivity parameter. Heat transfer rate decays for thermal stratification phenomenon. The current attempt is incorporated in diverse processes of industry and engineering including cooling and heating processes in solar water heater, building insulation, electronics, turbines, transportation, power generation, geothermal systems, and engines. Moreover, Sutterby model predicts the characteristics of pseudo-plastic and dilatant fluids. This model is very useful for high polymer solutions and polymer melts which are important industrial materials. Owing by such applications, the present examination has been established.

    更新日期:2019-12-31
  • Microstructural development and its effects on tensile properties of a high Ni TRIP steel produced by repetitive corrugation and straightening via rolling (RCSR)
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2019-12-31
    H. Abolfathi; H.R. Jafarian; H. Arabi; N. Park; A.R. Eivani

    Microstructural development and its effect on tensile properties of a Fe- 24Ni-0.3C Transformation Induced Plasticity (TRIP) steel subjected to repetitive corrugation and straightening via rolling (RCSR) process was investigated in this study. Microstructure developed during the application of one to 45 cycles of RCSR on TRIP steel sheets were analyzed by optical microscope and scanning electron microscope (SEM) equipped with electron backscatter diffraction detector and X-ray diffraction techniques. Results indicated that the volume fraction of martensite formed due to the deformation-induced by amplification of applied strain during RCSR process was about 75% accompanied with the formation of a large fraction of low angle boundaries. To study, tensile and hardness tests were carried out on several deformed samples their mechanical properties. The results also showed that after 40 cycles of the RCSR process, yield strength increased from 150 MPa in the starting material to 1157 MPa in the deformed state. As well, the uniform elongation reduced from 170% to 30% and the hardness value increased from 130 to 340 HV. This amount of improvement in tensile strength for this type of alloy by the application of RCSR has not been reported to date. Therefor the technique used in this research for the improvement of tensile properties can be very helpful for an alloy designer when very high tensile properties for a particular application is required.

    更新日期:2019-12-31
  • Phase-field simulation of effects of normal strain on the morphology and kinetics evolution of nanoscale phase
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2019-12-30
    Xinwen Tong; Yongsheng Li; Zhengwei Yan; Dong Wang; Shujing Shi

    This is the first investigation on the morphology and kinetics evolution of nanoscale precipitates under normal strain with the three-dimensional phase-field simulation. The volume fraction, particle number density and average particle radius of the precipitates are clarified for uniaxial, biaxial and triaxial strain, combining the free energy and shape change of nanoscale precipitates. For the anisotropic elasticity, uniaxial, biaxial and triaxial strain promote phase decomposition compared with strain-free state, except that triaxial compressive strain retards the early-stage precipitation. Nanoscale precipitates under mixed biaxial or triaxial strain display strip-like shape, especially for the biaxial tensile with uniaxial compressive strain. Triaxial tensile and compressive strain do not change the shape of precipitates, while the particle size is reduced under triaxial compressive strain. The results demonstrate that normal strain affects the morphology and kinetics of the nanoscale phase to different degrees.

    更新日期:2019-12-31
  • A comparative study on the microstructure and mechanical properties of fusion welded 9 Cr-1 Mo steel
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2019-12-30
    S. Madhavan; M. Kamaraj; B. Arivazhagan

    Modified 9 Cr–1 Mo is an ideal candidate preferred for high temperature applications in power plants. In this study, three P91 welds of 12 mm thickness are produced using Gas Tungsten Arc Welding (GTAW), Cold Metal Transfer (CMT) and Pulsed-CMT (P-CMT) processes. The impact toughness is evaluated in the as-welded as well as in the PWHT (760 °C-2 h) condition. It is found that P-CMT process resulted in the highest toughness in both the conditions. The heat input was maximum in the case of GTAW (800 J/mm) welds and minimum in CMT (330 J/mm). Even though P-CMT (380 J/mm) has heat input slightly above CMT, the former is compensated by higher welding speeds. Electron microscopy analysis revealed the presence of fine M23C6 and MX precipitates. Among the welds, P-CMT had minimal amount of the precipitates whereas GTAW welds had the maximum. The dimple morphology observed in the ruptured surface significantly varied and P-CMT process had finer dimples indicating finer weld microstructures and enhanced mechanical properties.

    更新日期:2019-12-31
  • Investigation of microstructural influence on entropy change in magnetocaloric polycrystalline samples of NiMnGaCu ferromagnetic shape memory alloy
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2019-12-30
    E. Villa; C. Tomasi; A. Nespoli; F. Passaretti; G. Lamura; F. Canepa

    Among NiMnGa-based quaternary systems, NiMnGaCu exhibits an interesting giant magnetocaloric effect thanks to the temperature overlapping of magnetic transition and thermoelastic martensitic transformation (TMT), in particular for compositions with ≈6 at% Cu content. In the present work polycrystalline alloy samples with Ni50Mn18.5Cu6.5Ga25 chemical composition were prepared. We present an extensive calorimetric and structural characterization to explore the correlation between microstructural properties and magnetocaloric response induced by means of selected thermal treatments, likely driven by the contribution of TMT to the magnetocaloric effect. Our results give important hints on how the efficiency of the martensitic transition and its modulation in temperature has a final effect on the total ΔS change.

    更新日期:2019-12-31
  • Effect of friction conditions on phase transformation characteristics in hot forging process of Ti-6Al-4 V turbine blade
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2019-12-30
    Shiyuan Luo; Qiang Wang; Po Zhang; Jia Li; Qinglong Liu

    This work is motivated by the fact that friction has a significant impact on the microstructures of titanium forged parts, further influencing their mechanical properties. In this paper, a 3D FE model is developed to investigate the phase transformation characteristics of Ti-6Al-4V turbine blade in the hot forging process. Then, the effect of friction conditions on temperature and phase transformations within the forged blade are analyzed numerically and verified by experiments. The results reveal that compared with a less influence on lamellar α + β phase, a good lubricated condition obviously increases the average volume fraction of α phase, while decreases the average values of temperature and β phase volume fraction as well as the distribution uniformities of α and β phases.

    更新日期:2019-12-30
  • Synthesis, morphological, spectral and thermal studies for folic acid conjugated ZnO nanoparticles: potency for multi-functional bio-nanocomposite as antimicrobial, antioxidant and photocatalytic agent
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2019-12-30
    Ola M. El-Borady; Ahmed F. El-Sayed

    The conjugations of ZnONPS with a biological surface-active substance, folic acid (FA), may achieve more biological activity and medical applications. Therefore, the current research was aimed to synthesis the ZnONPS then conjugated with FA by a facile chemical method. The morphological studies for free ZnONPS and [email protected] was performed using the (TEM), (SEM), (XRD), (EDX) and Zeta-potential. The spectral analyses were followed by UV–vis measurements and Photoluminescence (PL). The structural composition and conjugation strategies between ZnONPS and FA were observed by (FT-IR). The thermal stability was investigated using Thermo gravimetrical analysis (TGA). The antimicrobial efficacy and the minimum inhibitory concentration (MIC) were examined against 10 human pathogens. The NPS was investigated for photocatalytic degradation of methylene blue dye (MB). The antioxidant activity was detected. The results were showed nanocrystalline wurtzite possess quasi spherical NPS with size 16 nm (λmax = 373 nm, band gab 3.32 eV) after loading FA the sized increased by 2 nm with d spacing 0.3 nm. As FT-IR findings the FA and ZnONPS were linked via an amide bonding. The photo-degradation for MB after 180 min reached 82% and 85% for ZnONPS and [email protected], respectively. The antioxidant activity for nanocomposite was enhanced as well as the antimicrobial for E. faecalis and others more than free NPS. The results of MIC and MBC values were ranged from16 to 256 μg mL−1 and 16 to 512 μg mL−1, respectively. In conclusion, we can conclude that incorporation of FA to NPS was enhanced its antioxidant and antimicrobial potential leading it to be promising in many biomedical and food packaging applications.

    更新日期:2019-12-30
  • Mechanism and kinetics study of sulfuric acid leaching of titanium from titanium-bearing electric furnace slag
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2019-12-28
    Wenlin Nie; Shuming Wen; Qicheng Feng; Dan Liu; Yaowen Zhou

    Titanium(Ti)-bearing electric furnace slag (TEFS) was leached with sulfuric acid in this study. The influence of temperature, acid/solid ratio, particle size, and initial sulfuric acid concentration on the Ti extraction was evaluated. The leaching kinetics indicate that diffusion across the product layer and the interface transfer both affected the decomposition of the TEFS, and the apparent activation energy was24.01 kJ/mol. Reaction temperature was the most important factor that influenced the extraction of Ti, followed by the acid/solid ratio, sulfuric acid concentration, and particle size. The Ti leaching rate reached up to 89.46 % under the conditions of an average particle size of 31.5 μm, acid/solid ratio of 2.0:1, initial acid concentration of 88.0 wt%, reaction temperature of 513.15 K, and water leaching temperature of 333.15 K for 120 min. Fe was almost completely dissolved in the acid, whereas MgO (22.73 wt%) and Al2O3 (44.57 wt%) in spinel were retained in the leach residue, and SiO2 (45.94 wt%) and CaO (34.96 wt%) occurred in the form of diopside in the leach residue. During the leaching process, substantial TiOSO4 and CaSO4·2H2O were produced and coated the TEFS particles, which hindered the leaching of Ti.

    更新日期:2019-12-29
  • Bimetal-organic frameworks (Cux-Cr100-x–MOF) as a stable and efficient catalyst for synthesis of 3, 4-dihydropyrimidin-2-one and 14-phenyl-14H-dibenzo [a, j] xanthene
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2019-12-28
    Shady M. El-Dafrawy; Reda S. Salama; Sohier A. El-Hakam; Salem E. Samra

    Successful three-dimensional bimetallic metal organic frameworks with different Cu/Cr ratios have been prepared under solvothermal conditions using chromium nitrate and copper nitrate as a bimetal and 1, 4 benzene dicarboxylic acid as an organic linker. Numerous techniques were used to characterize the resulting samples such as XRD, BET, SEM, TEM, SEM-EDS and FT-IR measurements. Combination of Cu and Cr in the same framework will cause some deformation in the structure and decrease in the surface area and pore size distribution. This decrease may be due to the incorporated copper have higher atomic weight than chromium ion. The acidic properties can be measured by non-aqueous titration. The catalytic performance of bimetallic MOFs was confirmed through the synthesis of 3, 4-dihydropyrimidin-2-one and 14-Phenyl-14H-dibenzo [a, j] xanthene. pure Cu-BDC and Cr-MIL-101 possesses a relatively lower surface acidity as well as lower catalytic activity. It surprising that, the combination between copper and chromium in the same framework can significantly enhance the acidity and catalytic activity of the as-synthesized catalysts which may be due to the synergetic effect.

    更新日期:2019-12-29
  • Cold rolling deformation and annealing behavior of a β-type Ti–34Nb–25Zr titanium alloy for biomedical applications
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2019-12-28
    Sertan Ozan; Jixing Lin; Yaowu Zhang; Yuncang Li; Cuie Wen

    In this study, the microstructures and mechanical properties of a newly developed β-type Ti–34Nb–25Zr (TNZ) alloy after cold rolling at different reduction ratios and recrystallization annealing were investigated by optical microscopy, XRD, SEM, EBSD, hardness and tensile tests. The tensile strength of the TNZ alloys reached 1071 MPa after cold rolling, which is 1.4 times the tensile strength of the solution-treated alloy. The deformation mechanisms of the TNZ alloys were significantly affected by the cold rolling reduction ratio (CRRR). The dominant deformation mechanisms for the TNZ alloys cold rolled at 20% and 56% CRRR were the formation of kink bands and of stress-induced α” martensite. With increases in CRRR to 76%, the TNZ alloys showed a combination of deformation mechanisms including the formation of shear bands and stress-induced α” martensite, and {332} <113> β mechanical twinning. The TNZ alloy after cold rolling at 86% CRRR followed by annealing exhibited elongation at rupture of 18%, tensile strength of 810 MPa, Young’s modulus of 66 GPa, and toughness of 132 MJ/m3, making it attractive for biomedical applications.

    更新日期:2019-12-29
  • Effect of carbon nanotubes (CNTs) and silicon carbide (SiC) on mechanical properties of pure Al manufactured by powder metallurgy
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2019-12-28
    Heba Herzallah; Ayman Elsayd; Ahmed Shash; Mahmoud Adly

    In the present research, the effects of the size and amount of CNT and SiC particles on the mechanical properties of Al matrix composite were investigated. SiC of particle size 10 μm, CNT 10–40 nm, and Al powder of particle size less than 50 μm and purity 99.99% were used. Composites of Al with 3, 6, 9 and 12 wt.% SiC and 0.25, 0.5, 0.75, and 1 wt.% CNT were manufactured by powder metallurgy technique by cold compaction and vacuum sintering. Relative density, hardness, compression and friction coefficient were studied. The results of scanning electron microscope (SEM) and optical microscope observations illustrated that the distribution of the reinforcing particles was uniform. Moreover, increasing the amount of SiC and CNT leads to decreasing the relative density and improving the hardness and compressive strength of Al–SiC and Al-CNT composites.

    更新日期:2019-12-29
  • A comparative analysis of flow features of Newtonian and power law material: A New configuration
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2019-12-28
    Rashid Mahmood; S. Bilal; Afraz Hussain Majeed; Ilyas Khan; El-Sayed M. Sherif

    In recent years, material analysis of fluids has generated prodigious interest of researchers due to their effective role in interdisciplinary sciences. In view of its importance, the present communication is devoted to analyze the flow of power law fluid representing the features of shear thinning, shear thickening and Newtonian materials. Constitutive equations expressed in the form of tensorial representations depicting power law relation between viscosity and shear rate. The whole mathematical model is solved computationally via of finite element method by using stable P2−P1 finite element pair. A highly refined hybrid mesh is obliged for the accurate computation of results. Material properties of power law fluid are disclosed in physical configuration renowned as channel driven cavity combining various benchmark problems like cavity flow, forward and backward facing steps and channel flow. Impact of material parameters on pertinent profiles is disclosed through graphs. Verification of computed results is done by comparing the velocity, viscosity, pressure fields for power law fluid with the Newtonian case.

    更新日期:2019-12-29
  • The influence of manganese on the bake hardening of hot dip galvanized low carbon steels
    J. Mater. Res. Technol. (IF 3.327) Pub Date : 2019-12-26
    Rodrigo Rocha de Meira; Fabio Moreira da Silva Dias; Jefferson Fabrício Cardoso Lins

    This work is a study of the manganese influence on the aging behavior of hot rolled and hot dip galvanized low carbon steels. For this, two steels were evaluated, with Mn content ranged between 0.16% and 0.30%. The work was carried out on industrial scale, in order to verify the tendency of results obtained previously on studies performed on laboratory scale. The evaluation of the aging phenomenon was performed in two ways: accelerated aging tests on hot rolled steels and bake hardening tests on cold rolled and galvanized steels. In both tests, it was verified that the increase of the Mn content might be an effective option in the control of aging in aluminum killed steels, within the limits of the process variables used. In agreement with the results of the accelerated aging and bake hardening tests, a higher carbides’ volumetric fraction was observed in the steel with higher Mn content. The steel with higher Mn content presented an approximated mean bake hardening value of 43 MPa and an approximated mean carbides’ volumetric fraction of 0,02. The values related to the steel with lower Mn content was 64 MPa and 1% respectively. This work corroborates with previous studies, which indicates the manganese precipitates as important carbides nucleation sites, reducing the amount of solid solution carbon in the ferritic matrix, resulting in a higher aging resistance.

    更新日期:2019-12-27
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