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  • Stationary Shoulder Supporting and Tilting Pin Penetrating Friction Stir Welding
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2018-01-17
    Huijie Liu, Yanying Hu, Huan Wang, Shuaishuai Du, Dusan P. Sekulic
    更新日期:2018-01-17
  • Electrochemical micromachining on titanium using the NaCl-containing ethylene glycol electrolyte
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2018-01-17
    Weidong Liu, Hui Zhang, Zhen Luo, Chunfeng Zhao, Sansan Ao, Feng Gao, Yubo Sun

    Titanium has been widely applied in industry owing to its excellent properties such as low density, high strength, and corrosion resistance. Compared with traditional mechanical methods, electrochemical micromachining (EMM) has some inherent advantages for the shaping of hard metallic materials; therefore, it is a promising method for the micromachining of titanium. However, the high corrosion resistance of titanium owing to its stable oxide film is a drawback during EMM. To overcome this limitation, a novel electrolyte, NaCl-containing ethylene glycol (EG) solution, was applied in this study. The polarization behavior of titanium in the NaCl water-based and ethylene-glycol-based solutions was comparatively analyzed. In contrast to that in the water-based solution, no oxide film was formed during anodization in the NaCl-containing EG solution. This characteristic could potentially improve the machining performance of the EMM of titanium. Subsequently, the effect of the main process parameters on the machining performance was investigated. Accordingly, peak voltage of 40 V, pulse width of 25 μs, and feeding rate of 1 μm s-1 were selected as the optimum parameters. Using the optimum parameters, a high-quality microhole with 149.5 μm average diameter, 300 μm depth, and 7.6º taper angle was successfully EMM machined on titanium.

    更新日期:2018-01-17
  • Application of Ultrasonic Waves Towards the Inspection of Similar and Dissimilar Friction Stir Welded Joints
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2018-01-11
    Jaafar Tarraf, Samir Mustapha, Mohammad Ali Fakih, Mohammad Harb, Hongjian Wang, Georges Ayoub, Ramsey Hamade

    Crack detection in welded structures of dissimilar material using guided waves is not well developed. This paper scrutinizes the effect of material discontinuity in plate structures and the excessive plastic deformation, within friction stir welded (FSW) joints, on the propagation behavior of guided waves towards their application in weld assessment. Quantifying the scattering, attenuation and group velocities of the guided waves when they propagate across different media, as well as determining the elastic properties of the material within the weld will provide rich information about the behavior of ultrasonic waves. Three pristine defect free friction stir welded plates were used in this study. The first specimen was a weld of dissimilar materials aluminum/magnesium alloy (AA6061-T6/AZ31B), the second was of dissimilar aluminum alloy grades (AA6060/AA7020-T651), and the third was of the same aluminum grade (AA7020-T651/AA7020-T651). The elastic properties across all the welds were extrapolated using nano-indentation technique. Ultrasonic guided waves were excited and measured using piezoelectric wafers and laser Doppler vibrometer (LDV). Additionally, a sensor network design was implemented on the three specimens using piezoelectric transducers. Wave reflections, based on the LDV results and the information collected from the sensor network, were observed at the weld zone of the AA6061-T6/AZ31B FSW plate, while no reflections were detected at the weld zones in the AA7020-T651/AA7020-T651 and AA6060/AA7020-T651 plates. The results were correlated with the measurements obtained from the nano-indentation experiment, where a sharp change in the elastic properties of the base metals in the AA6061-T6/AZ31B welded joint were detected, unlike the other two plates that showed constant elastic properties across the weld zones. The results showed that the amount of scattering at the joints is a function of the wave propagation direction. It was noticed that the average wave reflection generated when the wave crossed from the AZ31B to the AA6061-T6 base metal was around 35% of the incident signal, but it reduced to 25% when the wave propagation direction was reversed. Characterizing ultrasonic waves in FSWs and the behavior of the incident and reflected waves in the welded zones will further improve on the technology used for inspection and monitoring of solid state welded joints.

    更新日期:2018-01-12
  • Reclamation of used Green Sand in small scale foundries
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2018-01-10
    Mohd Moiz Khan, Manvendra Singh, Sanjay M. Mahajani, G.N. Jadhav, Shashank Mandre

    Disposal of Used Foundry Green Sand (UFGS) remains one of the significant challenges faced by foundry industry nowadays. Experiments were performed to reduce the total clay content from 12% to as low as 2.2% in waste foundry sand. Three prototypes were developed during the course of this work. They include vertical fluidized bed, horizontal fluidized bed and a novel ball-mill type attrition and sieving unit. The cost per ton of reclaimed sand is higher in case of fluidized bed based prototypes while in case of attrition and sieving based prototype, it is less than half of the cost of the fresh sand. The experimental data generated on the two-stage attrition and sieving unit under different conditions is further used to arrive at a semi-empirical correlation and the optimum set of design and operating parameters to get the best performance.

    更新日期:2018-01-11
  • Experimental and Numerical Analyses of Formability Improvement of AA5182-O Sheet during Electro-Hydraulic Forming
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2018-01-09
    Arash Jenab, Daniel E. Green, Ahmet T. Alpas, Sergey F. Golovashchenko

    In the work presented, formability of electro-hydraulically formed AA5182-O aluminium sheet was investigated by means of grid analysis and numerical modelling. Sheet specimens of AA5182-O with 1.5mm thickness were formed using electro-hydraulic forming (EHF) process and the experimental results were compared with different forming limit curves (FLCs) and were used to calibrate a finite element model of EHF. It is found that the formability improvement of AA5182-O sheets were insignificant during EHF process. However, when specimens were electro-hydraulically formed with sufficient input energy into 34 or 40∘ conical dies, effective strain of safe grids increase by 40 and 70 percent when compared with conservative quasi-static FLC. Finite element simulation results suggests that a combination of different mechanical parameters contributed to the formability improvement. In case of die forming, the increased strain rate in areas close to the apex, negative stress triaxiality during the deformation and just before specimens contact the die and significant compressive through-thickness stress generated by high-velocity impact all contributed to the improvement of formability.

    更新日期:2018-01-10
  • Gap bridging of 6061 aluminum alloy joints welded by variable-polarity cold metal transfer
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2018-01-08
    Li Guojin, Zhang Peilei, Wu Xi, Nie Yunpeng, Yu Zhishui, Yan Hua, Lu Qinghua
    更新日期:2018-01-09
  • Metal plasticity and ductile fracture modeling for cast aluminum alloy parts
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2018-01-06
    Jinwoo Lee, Se-Jong Kim, Hyeonil Park, Hyuk Jong Bong, Daeyong Kim

    In this study, plasticity and ductile fracture properties were characterized by performing various tension, shear, and compression tests. A series of 10 experiments were performed using notched round bars, flat-grooved plates, in-plane shear plates, and cylindrical bars. Two cast aluminum alloys used in automotive suspension systems were selected. Plasticity modelling was performed and the results were compared with experimental and corresponding simulation results; further, the relationships among the stress triaxiality, Lode angle parameter, and equivalent plastic strain at the onset of failure were determined to calibrate a ductile fracture model. The proposed ductile fracture model shows good agreement with experimental results.

    更新日期:2018-01-07
  • Control of Mg2Sn formation through ultrasonic-assisted transient liquid phase bonding of Mg to Al
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2018-01-05
    Zhengwei Li, Zhiwu Xu, Dawei Zhu, Zhipeng Ma, Jiuchun Yan

    The formation of Al/Mg intermetallic compounds (IMCs) of Al3Mg2 and Al12Mg17 was successfully avoided through ultrasonic assisted transient liquid phase bonding Mg/Al using pure Sn interlayers. A new IMC of Mg2Sn formed in the joints. Different bonding parameters were used to control the formation of Mg2Sn. The optimum joint shear strength of 60.0 MPa was obtained at the temperature of 220 °C, ultrasonic power of Mode I and ultrasonic time of 4 s. The thickness of Mg2Sn should be depressed to less than 15% of the joint width. Joints were fractured through the Mg2Sn layer.

    更新日期:2018-01-06
  • Reflow-Oven-Processing of Pressureless Sintered-Silver Interconnects ☆
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2018-01-04
    Andrew A. Wereszczak, Branndon R. Chen, Brian A. Oistad

    A method was developed to pressurelessly fabricate strong and consistent sinterable-silver joints or interconnects using reflow oven heating. Circular sinterable-silver interconnects, having nominal diameter of 5-mm and 0.1-mm thickness were stencil printed, contact-dried, and then pressurelessly sinter-bonded to Au-plated direct copper bonded ceramic substrates at 250°C in ambient air. That sintering was done in either a reflow oven or a convective oven (latter being a conventional heating source for processing sinterable-silver). Consistently strong (> 40 MPa) interconnects were produced with reflow oven heating and were as strong as those produced with convective oven heating. This is significant because reflow oven technology affords better potential for continuous mass production and it was shown that strong sintered-silver bonds can indeed be achieved with its use.

    更新日期:2018-01-05
  • Hardening and softening effects in aluminium alloys during high-frequency linear friction welding
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2018-01-04
    Adrian Lis, Hideo Mogami, Tomoki Matsuda, Tomokazu Sano, Ryo Yoshida, Hisashi Hori, Akio Hirose
    更新日期:2018-01-05
  • Impact Butt Welding of NiTi and Stainless Steel- An Examination of Impact Speed Effect
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2018-01-03
    Qiao Li, Yuanxiang Zhu

    Decreasing the impact speed can extend the effective heating time and escalate the heating rate. Additional flash is generated near the NiTi/SS interface due to the lengthening of the effective heating time. With decreasing impact speed, the plastic deformation zone of the SS is enlarged, and the microstructure in the heat-affected zone (HAZ) is increasingly coarsened, but those of NiTi demonstrate the opposite trends. In all of the NiTi/SS joints, the weld consists of a diffusion layer with a thickness that increases slightly from 1 μm to 1.7 μm as the impact speed decreases from 40 mm/s to 27.5 mm/s. The mechanical properties of the joint deteriorate with decreasing impact speed due to the increased remnant of semi-molten NiTi at the interface. The joint welded at an impact speed of 40 mm/s has the highest strength of 522±41MPa with (7±2)% rupture elongation, and it fractures via micro-void coalescence.

    更新日期:2018-01-03
  • Microstructure and mechanical properties of robot cold metal transfer Al5.5Zn2.5Mg2.2Cu aluminium alloy joints
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2018-01-02
    Chaojie Xie, Shanglei Yang, Haobo Liu, Qi Zhang, Yuan Wang, Yuguo Zou

    Al5.5Zn2.5Mg2.2Cu aluminium alloys were butt welded using the robot cold metal transfer method. Optimal welding parameters were defined based on experiments to ensure penetration welding of low heat input. The morphology and evolution of the microstructure, mechanical properties and fracture behaviour of the welded joint after 360 h of natural ageing were investigated. The experimental results indicate that a Mg2Si phase existed in the weld zone, a large amount of MgZn2 in the solid solution zone near the weld dissolved into the Al matrix and MgZn2 precipitated in the overageing softening zone. Compared with the base metal, the matrix of the solid solution zone mainly consisted of coarse precipitates, η precipitates were continuously distributed in the grain boundaries, and a precipitate-free zone was not obvious. Coarse and discontinuous precipitates were distributed in the grain boundary of the overageing softening zone, and the width of the precipitate-free zone became larger with coarsening of the grain boundary precipitates in the overageing softening zone. The mechanical properties were measured by using local samples extracted from the base metal, heat affected zone and welded zone. The base metal had the highest tensile strength and yield strength, in contrast with the welded zone. The tensile strength of the heat affected zone was 92% that of the base metal, and its elongation was increased by 16.7% due to the coarsening of the grain boundary precipitates in the heat affected zone.

    更新日期:2018-01-03
  • A comparative study of microstructure and tensile properties of Ti2AlNb joints prepared by laser welding and laser-additive welding with the addition of filler powder
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2018-01-02
    Zhenglong Lei, Kezhao Zhang, Heng Zhou, Longchang Ni, Yanbin Chen

    The influence of the addition of filler powder on the microstructure and properties of laser-welded Ti2AlNb joints was comparatively investigated using scanning electron microscopy, transmission electron microscopy, electron back scattered diffraction, and tensile tests. The heat affected zone (HAZ) of laser-additive-welded joints was divided into B2, B2+α2, and B2+α2+O — three regions with increasing distance from the fusion line. The HAZ of laser-welded joints could only be divided into two regions, viz., B2+α2 and B2+α2+O. The microstructure of the fusion zone was composed of a single B2 phase for both laser welding and laser-additive welding. Columnar grains were observed in the fusion zone of laser-welded joints, while the B2 grains in the fusion zone of laser-additive-welded joints were basically equiaxed. A misorientation angle distribution analysis showed that the fraction of high-angle grain boundaries of laser-additive-welded joints was higher than that of laser-welded joints. The addition of filler powder promoted heterogeneous nucleation during solidification in laser-additive welding. Following tensile tests at room temperature, failure tended to occur in the fusion zone of the laser-welded joints and in the HAZ of the laser-additive-welded joints. The laser-additive-welded joints exhibited better tensile properties because of the higher Mo content as well as the equiaxed microstructure of the fusion zone.

    更新日期:2018-01-03
  • Influence of SLM process parameters on the surface finish, porosity rate and fatigue behavior of as-built Inconel 625 parts
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-30
    Imade Koutiri, Etienne Pessard, Patrice Peyre, Ouafae Amlou, Thibaut De Terris

    This paper is dedicated to understanding fatigue crack initiation for an Inconel 625 manufactured by SLM, using a hatching + contour procedure. In the first part of the paper, an optimum set of parameters was found to deliver the best surface roughness combined with low porosity. This process optimization, mostly focused on adjusting the volume energy density aimed at finding a compromise between an optimum densification state and a minimum number of contaminating spatters. Secondly, a fatigue test campaign has been conducted on as-built SLM samples or polished samples. The analysis of failure surfaces allowed identifying different heterogeneities at the origin of the fatigue damage for each configuration. The embedded particles on the surface of as-build specimens have been shown to play an important role in fatigue and need to be optimized or taken into account in the fatigue strength design of SLM components.

    更新日期:2017-12-31
  • Roll-bonding of metal-polymer-metal sandwich composites reinforced by glass whiskers at the interface
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-30
    Saeed Mousa, Nathan Scheirer, Gap-Yong Kim

    Metal-polymer laminate composites are widely used in various industries, including automobile, aerospace, marine and civil construction because of their high specific stiffness and strength, and excellent fatigue and corrosion properties. In this study, glass whisker dispersed metal-polymer-metal laminated composites have been fabricated using the warm roll-bonding (WRB) process as roll bonding can provide advantages over other techniques due to its simplicity and scaling capability. The reinforcing effects of the glass whisker on the adhesion strength and shear resistance were analyzed. A small punch test (SPT), single lap shear test, and T-peel test were used to evaluate the mechanical and bonding properties, and electron microscopy was employed to analyze the fracture behavior of the whisker-reinforced laminate composites. The shear strength of the glass whisker reinforced sandwich composite improved nearly 40% when compared with the unreinforced samples. The SPT results showed increase in the ultimate load, specific load, and specific fracture energy for the samples with glass whiskers incorporated between the roll-bonded layers.

    更新日期:2017-12-31
  • The Correction of Temperature-Dependent Vickers Hardness of Cemented Carbide Base on the Developed High-Temperature Hardness Tester
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-30
    Bicheng Guo, Libin Zhang, Liang Cao, Tao Zhang, Feng Jiang, Lan Yan

    In this study, a high-temperature hardness tester was developed, and its basic structure, main performance and advantages were introduced. The high-temperature hardness tester has three main advantages: it significantly prevents the oxidation of the sample and the indenter; it does not affect the stiffness of the bearing platform; and ensures the accurate measurement of the relevant image at high temperatures. Then, the Vickers indentation test was carried out using the developed hardness tester. The contact surface of the indenter and the sample was found to be a curved surface, and the height of the middle of the indentation edge was found to be higher than the height of the indentation corner. Therefore, a three-dimensional model of indentation morphology was established, and hardness values at different temperatures were corrected. It was found that the hardness of CTS18D cemented carbide decreased with increasing temperature, and the value decreased by approximately 35% from room temperature to 1,000°C. In addition, at the same temperature, the corrected hardness value was smaller than the measured hardness value. Moreover, the difference value between the measured hardness and the corrected hardness decreased from 3.9% to 3.2% with an increase in temperature from 26°C to 1,000°C.

    更新日期:2017-12-31
  • Study on AA5182 aluminum sheet formability using combined quasi-static-dynamic tensile processes
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-30
    Guangyao Li, Huakun Deng, Yunfei Mao, Xu Zhang, Junjia Cui
    更新日期:2017-12-31
  • Assessment of friction stir welding aluminium t-joints
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-29
    J.S. Jesus, J.M. Costa, A. Loureiro, J.M. Ferreira
    更新日期:2017-12-31
  • The evolution of the microstructure in AISI 304L stainless steel during the flat rolling – modeling by frontal cellular automata and verification
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-25
    Łukasz Łach, Jarosław Nowak, Dmytro Svyetlichnyy

    The use of appropriate forming processes allows to obtain materials of required shapes, structures and properties. The technological conditions of the process can be optimized in view of the final microstructure. It can be achieved using different modeling methods, but recently use of cellular automata remains on the high level of interest. The aim of the study is a development and verification of the model of microstructure evolution during the flat rolling process. The microstructural model is based on frontal cellular automata, which uses for simulation of the rolling process of AISI 304L stainless steel. Modeling can be done on the basis of the general characteristics of the process i.e. the information about the duration of plastic deformation, time intervals between the passes, temperature and strain rate. The paper presents the modeling results of flat rolling process of AISI 304L stainless steel for different processing conditions. The modeling of three passes is presented. The results of the microstructure evolution can be observed as the microstructure maps at the selected time moments, as well as changes of average grain size, grain size distribution, fraction of recrystallization and flow stress. Some of the simulation results are verified with the experimental data. Model shows the high flexibility, allowing to take into account the various processing parameters. Simulation results are similar to the real processing conditions. It can be considered as a new tool for the development and optimization of flat rolling in view of final microstructure.

    更新日期:2017-12-27
  • Microstructure and corrosion resistance of Al5083 alloy hybrid Plasma-MIG welds
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-24
    Detao Cai, Shanguo Han, Shida Zheng, Ziyi Luo, Yupeng Zhang, Kai Wang
    更新日期:2017-12-27
  • Effect of interlayer thickness on the microstructure and strength of WC-Co/Invar/316L steel joints prepared by fibre laser welding
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-24
    Guotao Yin, Peiquan Xu, Hongying Gong, Haichao Cui, Fenggui Lu

    Increasing the thickness of the Invar (Ni42Fe50.9C0.6Mn3.5Nb3) interlayer from 1 to 1.5 mm resulted in a continuous metallurgical bonding, free of voids and oxide films. Invar as a pre-placed buffer also led to higher bending strength because of the stress relaxation. When the thickness was increased to 2 mm, the porosity in the fusion zone increased and cracks developed near the fusion boundary on the WC-Co side, lowering the strength. The fusion boundary, heat affected zone and the fusion zone on the WC-Co side were susceptible to cracking. Transmission electron microscopy revealed high densities of dislocations. Energy dispersive spectroscopy suggested that long-range solute diffusion occurred inside the WC grains and at the WC/Fe (Ni)/WC interfaces.

    更新日期:2017-12-27
  • The mechanisms of arc coupling and rotation in cable-type welding wire CO2 welding
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-24
    Zhidong Yang, Chenfu Fang, Mingfang Wu, Kai Qi, Yong Chen, Ruixiang Ma

    In the cable-type welding wire CO2 welding process, the arc coupling and rotation behaviors are greatly different from those in typical single-wire CO2 welding. A deflection length model is proposed to explain the phenomenon of arc shape interaction and coupling, which is considered to be caused by a concentration of forces at the central wire resulting from the electromagnetic forces generated by the currents running through the individual wires. The arc rotation is influenced by the compositional characteristics of the cable-type welding wire as the wire is fed, resulting in self-rotation as the wire melts. The arc stability, the droplet transfer behavior and the weld pool are affected by the balance of the forces during the welding process and cause the arcs from the cable-type welding wire to couple together, resulting in a stable arc and stable droplet transfer. The combined forces acting on the weld pool are beneficial for the transfer of arc heat and droplet heat to the side and bottom of the molten pool, affecting the weld pool and weld formation.

    更新日期:2017-12-27
  • Effects of Hollow Structures in Sand Mold Manufactured Using 3D Printing Technology
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-24
    Chengyang Deng, Jinwu Kang, Haolong Shangguan, Yongyi Hu, Tao Huang, Zhiyong Liu

    The performance of 3D printed sand molds with internal hollow structures was studied. The influence of the internal hollow structures (a single layer air cavity or multilayer air cavities) on heat flux was theoretically analyzed and numerically simulated using COMSOL software. Better insulation effect was achieved by reducing the cavity spacing, and multilayer air cavities performed better than a single layer air cavity. 3D printed sand molds with these hollow structures for a stress-frame casting and a bar-shaped casting were designed and poured with aluminum alloy A356 melt. The solidification time of the riser surrounded by three layers of air cavities was prolonged by over 30%, and its feeding function during solidification was significantly improved. The temperature difference within the stress-frame casting was decreased using three layers of air cavities surrounding its thin rods, resulting in a 40% reduction of the residual stress in the thin rods. Open air cavity structure was used for air blowing during the solidification process to increase the cooling rate of one thin rod of the cast specimen, and its secondary dendrite arm spacing was narrowed.

    更新日期:2017-12-27
  • Role of thermal-mechanical loading sequence on creep aging behaviors of 5A90 Al-Li alloy
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-24
    J. Fu, H. Li, C. Lei, G.W. Zheng, T.J. Bian, L.H. Zhan

    Creep age forming (CAF), under thermal-mechanical environment, may be sensitive to the thermal and mechanical loading conditions. Unfortunately, the different creep aging (CA) behaviors under two inverse thermal-mechanical loading sequences, viz. loading-heating (LH) and heating-loading (HL), are almost neglected in experiments or modeling of CAF. In this work, taking solution treated 5A90 Al-Li alloy as a case material, the loading sequence related CA behaviors of the alloy are investigated using continuous/interrupted tensile CA tests at 130 °C/175 MPa combined with high-resolution Transmission Electron Microscope (HRTEM) and mechanical properties tests. The results show that, the inverse loading sequences result in different initial tempers for CA process, viz. solution temper under LH and stress-free aged temper under HL. The solution temper for CA process under LH can lead to a more stable and repeatable CA process than HL does, which causes a stress-free aged temper with randomly and discretely distributed precipitates for CA process. After two inverse loadings and 18 h of isothermal CA, the total creep deformation for LH (0.1475%) is twice larger than that for HL (0.0720%), thanks to the remarkable creep strain in the LH non-isothermal CA process with 49.2% of total creep strain. The samples under LH present a lower strength and a higher elongation than those under HL during the whole process, and the gap of the mechanical properties of samples under the two loading sequences reaches its maximum (15 MPa for yield strength and 8.45% for elongation) after 0.5 h of isothermal CA, and then gradually decreases in subsequent process. After 0.5 h of isothermal CA, though the volume fraction of the δ′ precipitates (Al3Li) under LH is larger than that under HL, the dislocations density under LH is less than that under HL, which makes a lower material strength under LH. It is noted that, after 18 h of isothermal CA, the microstructures and macroscopic mechanical properties of the samples have less disparity for the two inverse loading sequences.

    更新日期:2017-12-27
  • Material flow visualization and determination of strain rate during friction stir welding
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-24
    Rahul Kumar, V. Pancholi, R.P. Bharti

    Particle image velocimetry (PIV) technique was adopted to understand material flow and measure strain rate around the tool pin during friction stir welding (FSW). The micro-spherical glass tracers in a transparent visco-plastic material, of almost similar densities, were used as experimental materials. The characteristics of material flow, in particular, flow velocity and strain rate were obtained by following the path of the tracer particles. A rotational zone around the tool pin was observed due to large deformation of the material close to the tool pin. The maximum velocity was noted to be 60% (close to the pin surface) of the pin peripheral velocity, and strain-rate was found to be 20 s-1 (0.6 mm away from the pin periphery) at FSW parameters of 170 rpm and 50 mm min-1. The strain rate was found to increase from 8 s-1 to 44 s-1 with increase in rotational speed from 75 rpm to 425 rpm. Predictive correlations were established for variations of velocity and maximum strain-rate as a function of rotational, traverse speeds and distance away from the tool pin surface. Overall, it was established that PIV technique can be utilized for the understanding of material flow and strain-rate behaviour during FSW. Furthermore, this technique enabled in-situ visualization overcoming drawbacks of other techniques reported in the literature.

    更新日期:2017-12-27
  • 更新日期:2017-12-22
  • Advancing electrochemical jet methods through manipulation of the angle of address
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-20
    J. Mitchell-Smith, A. Speidel, A.T. Clare
    更新日期:2017-12-21
  • Improvement of Magnesium Alloy Edge Cracks by Multi-cross Rolling
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-20
    Chenchen Zhi, Lifeng Ma, Qingxue Huang, Zhiquan Huang, Jinbao Lin

    In order for the edge cracks during the AZ31 Mg alloy rolling to be reduced, the hot-rolling microstructure and texture were modified through multi-cross rolling (MCR) during the deformation. The AZ31B magnesium alloy sheets were hot rolled at a temperature ranging from 250℃ to 400℃ and at a rolling speed of 0.5m/s. Four different multi-cross rolling (MCR) routes were selected in the test. The macroscopic morphology, microstructure and texture of the as-rolled AZ31B sheets were characterized to investigate the edge-crack behavior during the rolling with various rolling routes and temperatures. Through the various rolling routes comparison, the grain size, the texture and the twins were the main factors that affected the cracks. It was demonstrated that the grain refinement and weak basal textures obtained by RII where the rolling direction was changed by 90° between two adjacent passes, could significantly reduce the edge cracks during the the rolling at an elevated temperature. When rolling with RII at 400℃, no apparent edge cracks appear on the sheet rolled with four passes.. The propagation mechanism of the crack tips was studied in details at the temperature of 350℃, whereas the results demonstrated that a high-sized area of grain boundaries in-between the finer grains could increase the crack propagation resistance.

    更新日期:2017-12-21
  • Vibration-assisted micro-ECM combined with polishing to machine 3D microcavities by using an electrolyte with suspended B4C particles
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-19
    Zhao-zhi Wu, Xiao-yu Wu, Jian-guo Lei, Bin Xu, Kai Jiang, Jin-ming Zhong, Dong-feng Diao, Shuang-chen Ruan

    Three-dimensional (3D) microcavities can be machined by micro-electrochemical machining (micro-ECM) using a 3D microelectrode. However, with increasing machining depths, it becomes challenging to renew electrolyte and remove the electrolytic products from the machining gap. Therefore, 3D microcavities are usually shallow and the machined surfaces are of poor quality. To address these problems, this paper proposed performing 3D microelectrode vibration-assisted micro-ECM in combination with polishing to machine 3D microcavities by using an electrolyte containing suspended B4C particles. First, a 3D microelectrode with rectangular holes on both of its undersurfaces was fabricated by means of bending-and-avoiding mode wire electrical discharge machining in combination with vacuum thermal diffusion bonding. Second, the prefabricated microelectrode was applied in vibration-assisted micro-ECM to machine deep 3D microcavities using an electrolyte containing suspended B4C particles. Thereafter, the machined surfaces of the deep 3D microcavities were polished to improve the surface quality. Furthermore, the effects of vibration amplitude and frequency, polishing time, and B4C particle concentration on the microcavity surface quality were investigated in detail. The experimental results indicate that the electrochemical reaction attachments on the microelectrode surface were removed by polishing of the particles during processing, ensuring satisfactory processability of the microelectrode, as well as a highly efficient and stable micro-ECM process. Moreover, when the vibration amplitude was set to 10 μm, vibration frequency to 30 Hz, polishing time to 30 min, and B4C particle concentration to 5 g/L for the 300 μm deep microcavity machined by the proposed method, the microcavity bottom surface roughness was minimized (Ra = 0.223 ± 0.021 μm) and the sidewall roughness was improved. Finally, based on the proposed method and optimized polishing parameters, 3D microcavities of more than 800 μm deep with rectangular and semi-cylindrical islands were obtained.

    更新日期:2017-12-20
  • Heat Transfer Simulations of Selective Laser Melting Process Based on Volumetric Heat Source with Powder Size Consideration
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-19
    Hong-Chuong Tran, Yu-Lung Lo

    Three-dimensional finite element heat transfer simulations with new volumetric heat source are performed to estimate the size of the melt pool cross-section during Selective Laser Melting (SLM). The simulations are based on a new volumetric heat source which takes into account the effect of the powder size distribution on the propagation of the laser energy through the depth of the metal powder layer. In modeling the volumetric heat source, a modified sequential addition method is used to construct the metal powder layer with different powder particle sizes and the absorptivity profile along the depth of the powder layer is then calculated by means of Monte Carlo ray-tracing simulations. It is shown that the peak melt pool temperature obtained in the present simulations (3005 K) is in better agreement with the experimental value than that obtained in previous simulation studies. Furthermore, the peak temperature is lower than the evaporation point of the powder particle layer, and is hence consistent with the stable melt track reported in experimental studies. To further confirm the validity of the proposed finite element heat transfer model, the simulation results obtained for the contact width between the melt pool and the substrate and the width of the powder-consumed band are compared with the experimental results and simulation findings presented in the literature. Finally, simulations are performed to predict the stability condition of a single scan melt track in the SLM process. The prediction results are shown to be consistent with the experimental findings.

    更新日期:2017-12-20
  • Review of friction modeling in metal forming processes
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-18
    C.V. Nielsen, N. Bay

    In metal forming processes, friction between tool and workpiece is an important parameter influencing the material flow, surface quality and tool life. Theoretical models of friction in metal forming are based on analysis of the real contact area in tool-workpiece interfaces. Several research groups have studied and modeled the asperity flattening of workpiece material against tool surface in dry contact or in contact interfaces with only thin layers of lubrication with the aim to improve understanding of friction in metal forming. This paper aims at giving a review of the most important contributions during the last 80 years covering experimental techniques, upper bound solutions, slip-line analyses and numerical simulations. Each of the contributions shed light on the importance of the real contact area and the influencing parameters including the material properties, surface conditions, normal pressure, sliding length and speed, temperature changes, friction on the flattened plateaus and deformation of the underlying material. The review illustrates the development in the understanding of asperity flattening and the methods of analysis.

    更新日期:2017-12-18
  • Dimensionless parameters controlling fluid flow in electromagnetic cold crucible
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-18
    Ruirun Chen, Yaohua Yang, Qi Wang, Hongsheng Ding, Yanqing Su, Jingjie Guo

    A 3-D numerical model was established for predicting the flow field in a square electromagnetic cold crucible (EMCC) used for melting and directionally solidifying TiAl alloys. Four dimensionless parameters that characterise the melt flow in the EMCC were derived, those being the Hartman (Ha), magnetic Reynolds (Rω), coils-melt position (h) and the ratio of the melt height to length (H/L) numbers. Parametric simulations and experiments were carried out to understand the effects of processing parameters such as the intensity and frequency of the current, the relative coils-melt position and the melt shape on the flow field. The meridional flow normally consists of two vortices in the half meridian plane, the lower vortex decreases with increasing Ha, Rω and h (hb>hm h b > h m ), as well as decreasing H/L. Higher Ha, H/L and lower h induce intensive fluid flow in the melt due to the stronger EM coupling, which could promote the uniformity of solute in the melt. The turbulence kinetic energy is significantly influenced by the length scale of the turbulent flow and the flow velocity in the melt, it increases with increasing Ha, h and H/L, while reduces and tends to be stable at higher Rω. Relatively higher flow velocity and turbulence kinetic energy can be obtained when Rω is close to 10. The weakened flow in the vicinity of solid/liquid interface under lower Ha and Rω, as well as higher h and H/L is beneficial for continuous growth of columnar crystals during the directional solidification process.

    更新日期:2017-12-18
  • A novel surface microtexture array generation approach using a fast-tool-feeding mechanism with elliptical cam drive
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-17
    S.T. Chen, Y.H. Tung, J.R. Jiang

    This paper presents the development and application of a reciprocating fast-tool-feeding mechanism with elliptical cam drive for rapidly fabricating surface microtexture arrays. Four kinds of different drive-mechanisms involving piston-rod, eccentric-cam, swash-plate-cam, and elliptical cam are devised and analyzed. The elliptical cam is employed as the drive mechanism for the reciprocating feed-tool system. Its symmetrical structural design suppresses systematic vibration, allowing for stable high-acceleration motion, and a speed of response double that of the other tool systems. Finite Element Analysis (FEA) is conducted to predict weaknesses, potential deformation problems, and the resonant frequency of the developed mechanism. Tool trailing stress is derived from the relationship between cutting force normal to the shear plane as well as cutting depth. It is shown that the predicted cutting force fits the required work current. Experimental verifications involving microdimple array generation are implemented to verify the practicability of the feed-tool system. Experimental results demonstrate that a microdimple array of 12×34 is promptly finished at a drive-frequency of 10 Hz, workpiece speed of 1200 mm/min, cutting depth of 30 µm, and processing time of only 40 seconds. These approaches and conditions generated surface microtexture arrays with highly consistent micro features confirming that the developed reciprocating fast-tool-feeding mechanism is well suited to the high reproducibility of consistently precise machined dense microstructure arrays.

    更新日期:2017-12-18
  • Microstructure and mechanical properties of double-wire + arc additively manufactured Al-Cu-Mg alloys
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-16
    Zewu Qi, Baoqiang Cong, Bojin Qi, Hongye Sun, Gang Zhao, Jialuo Ding

    As the properties of wire + arc additively manufactured Al-6.3Cu alloy cannot meet the applying requirements, a double-wire + arc additive manufacturing system was built to add magnesium into Al-Cu deposits for higher mechanical properties. Two commercial binary wires aluminum-copper ER2319 and aluminum-magnesium ER5087 were chosen as the filler metal to build Al-Cu-Mg components with different compositions by adjusting the wire feed speed. The microstructure and morphology of thin wall samples were characterized by optical micrographs (OM), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The Vickers hardness and tensile properties were investigated. The microstructure of Al-Cu-Mg deposits was mainly composed of coarse columnar grains and fine equiaxed grains with non-uniformly distributing characteristics. With higher Cu but lower Mg content, the strengthen phase turned to Al2Cu + Al2CuMg from Al2CuMg, and the micro hardness presented an increasing trend. The isotropic characteristics of ultimate tensile strength (UTS), yield strength (YS) and elongation were revealed in these samples. The UTS was about 280±5 MPa both in horizontal and vertical directions for all samples. The YS showed an increasing trend from 156MPa to 187MPa with the same content trend, while elongation decreased from 8.2% to 6%. The fractographs exhibited typical brittle fracture characteristics.

    更新日期:2017-12-18
  • Benchmarking strength and fatigue properties of spot impact welds
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-14
    Angshuman Kapil, Taeseon Lee, Anupam Vivek, John Bockbrader, Tim Abke, Glenn Daehn
    更新日期:2017-12-14
  • Effect of active fluxes on thermophysical properties of 309L stainless-steel welds
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-14
    Bin Wu, Bin Wang, Xieting Zhao, Huan Peng

    The thermal history during the A-TIG welding and thermophysical properties of 309L stainless steel were measured using infrared thermometry and a thermal conductivity analyzer. A Manual-HKS weld scanner was introduced to detect the fluctuation of welding parameters, and changes in welding current were analyzed. The mean temperature at the measuring point increased when an active agent was added to the coating layer. Weld penetration increased from 2.8 mm to 5.24 mm compared with conventional tungsten inert-gas welding. The thermophysical properties of weld beads were switched with different contents of calcium fluoride, effusivity, thermal conductivity and diffusivity decreased with increasing calcium fluoride, a reverse was observed for calcium fluoride surpassed 3 wt.%. The microstructure of the welded region was found to contain equiaxed ferrite due to the proper heat applied and alloying element distribution. The obtained results can illuminate the mechanisms of penetration increase and changes in physical properties of weld beads.

    更新日期:2017-12-14
  • Numerical Simulation of the Formation of Hourglass Welds during Laser Welding
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-14
    Bon Seung Koo, Pornsak Thasanaraphan, Herman F. Nied

    The purpose of this study is to understand the effect of laser welding parameters on the formation of hourglass shaped welds in low carbon steel. Transient laser welding is modeled in ANSYS to simulate the coupled heat-transfer/fluid-flow behavior that produces corresponding hourglass shaped melt pool geometry. Characteristics of the hourglass mode are full narrow penetration and wide surface of molten pool. Recoil pressure induced by rapid metal vaporization strikes the melt pool to form a deep and narrow key hole. Simultaneously, surface tension minimizing its surface free energy primarily acts to widen the melt pool. Comparison of the weld geometries show that welding parameters associated with changes in the melt fluid dynamics are of great importance in the formation of the hourglass shaped melt pool during laser welding.

    更新日期:2017-12-14
  • Clear to clear laser welding for joining thermoplastic polymers: a comparative study based on physicochemical characterization
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-13
    Jens De Pelsmaeker, Geert-Jan Graulus, Sandra Van Vlierberghe, Hugo Thienpont, Danny Van Hemelrijck, Peter Dubruel, Heidi Ottevaere

    The joining of materials is essential to many industrial applications used today. However, it still lacks a reliable and true single step method to join different types of materials including polymers. Laser welding was primarily employed for metals until some decades ago, but with the rise of high power solid state lasers, applications have emerged in the polymer field. With the recent addition of fiber lasers, true clear to clear welding, joining two of the same transparent polymer layers, has become feasible at a different wavelength range, which benefits the sealing of microfluidic devices. A number of research efforts were made at performing welds of thermoplastics at this wavelength range, however without attempts at offering elaborate explanation of the observations. In our work, a laser welding system using a Thulium fiber laser at 1940 nm was used to join a variety of thermoplasts, without the use of additives or prior processing. By optically and chemically characterizing the materials, a basis was established that links intrinsic material properties to observed welding performance, as determined by mechanical shear tests on the welded materials. We found that four of the ten considered thermoplastic polymers lend themselves to sufficiently strong bonding to allow the creation of leak-proof microfluidic devices by use of laser welding at this wavelength.

    更新日期:2017-12-14
  • High-temperature deformation of delta-processed Inconel 718
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-12
    Pedro Páramo-Kañetas, Utkudeniz Özturk, Jessica Calvo, José María Cabrera, Martha Guerrero-Mata

    The hot-flow behavior of Inconel 718 subjected to delta processing (DP) was analyzed. Hot compression tests were subsequently performed at 960 °C and 1020 °C at the four different strain rates of 0.001, 0.01, 0.1, and 1 s-1. The two deformation temperatures were located below and above the δ-solvus of IN718 respectively. Microstructural characterization was performed by means of optical (OM) and scanning electron microscopy (SEM). The high temperature deformation results in the fragmentation of the existing δ-phase by means of partial dissolution and/or deformation, leading to an improved grain size control. A classic dynamic recrystallization (DRX) behavior was observed in the flow curves, which is typical of low-medium stacking fault energy (SFE) alloys. This flow behavior was modeled according to various approaches. Peak stress modeling was performed using two different approaches, referred to as ‘apparent’ and ‘physically-based’. The hot-flow behavior before the peak stress was modeled according to the Estrin-Mecking-Bergstrom approach, with Avrami kinetics employed to describe the DRX behavior.

    更新日期:2017-12-14
  • Microstructure and mechanical properties of Cf/Al-TiAl laser-assisted brazed joint
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-12
    Guangjie Feng, Zhuoran Li, Zhi Zhou, Yong Yang, Dusan P. Sekulic, Michael R. Zachariah
    更新日期:2017-12-14
  • A study on EDM debris particle size and flushing mechanism for efficient debris removal in EDM-drilling of Inconel 718
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-12
    M. Tanjilul, Afzaal Ahmed, A. Senthil Kumar, M Rahman

    Electrical discharge machining (EDM) is a non-contact machining process that removes material through spark erosion and is often used for drilling holes in difficult-to-cut materials such as Nickel-based super alloys. However, this process becomes slower with the increase of the hole depth. This is because the flushing pressure becomes inefficient for the effective evacuation of process debris leading to secondary discharges and resulting in increased machining time. This study presents an innovative simultaneous flushing and vacuum-assisted debris removal system, which facilitates better debris removal for deep-hole EDM drilling. Improvement in the drilling time and better surface roughness have been achieved using the developed setup. To evaluate the performance of the vacuum-assisted debris removal system, a novel computational fluid dynamics model is also proposed in this study. Experimentally measured particle size data of full length scale act as a reference for the proposed numerical model.The analysis presented in this study provides significant insight into sizes of the debris particles in different machining conditions, in full length scale using an automated image processing technique. The presented numerical model can be used to investigate the various factors influencing the removal of debris from the machining zone. The experimental and numerical components of this research complement each other in the design of the presented vacuum-assisted debris removal system.

    更新日期:2017-12-14
  • Effects of lubricant on the IHTC during the hot stamping of AA6082 aluminium alloy: experimental and modelling studies
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-11
    Xiaochuan Liu, Omer El Fakir, Lichun Meng, Xiaoguang Sun, Xiaodong Li, LiLiang Wang
    更新日期:2017-12-14
  • Effect of TIG current on microstructural and mechanical properties of 6061-T6 aluminium alloy joints by TIG–CMT hybrid welding
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-08
    Ying Liang, Junqi Shen, Shengsun Hu, Haichao Wang, Jie Pang

    In order to expand the direct current-cold metal transfer (DC-CMT) method to include large-thickness plate welding, a tungsten inert gas–CMT (TIG–CMT) hybrid welding process was employed in this work. Adding a stable TIG arc can increase the total heat input on the workpiece and the penetration capacity of the DC-CMT welding process. Al6061 plates 4 mm thick were welded successfully by this method. As the TIG current increased, the heat input of the welding process increased. The effect of TIG current on the microstructure and mechanical properties of the joints was investigated. The hardening phase in Al6061 was sensitive to the heat input provided by the welding process. Because of microstructural transformation, a decrease in the mechanical properties (softening phenomenon) invariably appeared in the heat-affected zone (HAZ). With increasing TIG current, the microstructures of the joints coarsened, and the width of the partially melted zone (PMZ) and HAZ of the joints broadened. A precipitation strengthening phase of Mg2Si appeared in HAZ. The hardness curve of the joint presented roughly W-type distribution. The hardness obtained in the softened zone was approximately 50% that of the base metal (BM). The joints demonstrated good deformation capability before fracture. As compared to the base material, the strength and the elongation of the joints decreased approximately 40% and 50%, respectively.

    更新日期:2017-12-14
  • Non-dimensional modeling of the effects of weld parameters on peak temperature and cooling rate in friction stir welding
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-08
    Bryan J. Stringham, Tracy W. Nelson, Carl D. Sorensen

    Experimental data from friction stir welded Al 7075 and HSLA-65 were used to create dimensionless, empirical models relating critical weld parameters to the peak temperature rise and cooling rate of the weld heat-affected zone. Five different backing plate materials and a wide range of travel speeds and weld powers were used in the experimental design to ensure the models are relevant to a broad range of welding parameters. The resulting models have R-squared values of 0.997 and 0.995 for the dimensionless peak temperature rise and cooling rate correlations, respectively. Demonstrations of the models’ practical applications are provided. Herein is shown how the models can identify welding parameter (i.e. travel speed or power) levels needed to produce a desired weld peak temperature rise or cooling rate. Also demonstrated is how the models can be used to explore the relative effects of travel speed and backing plate thermal diffusivity on weld peak temperature rise and cooling rate.

    更新日期:2017-12-14
  • Phase field modeling of solidification microstructure evolution during welding
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-07
    Fengyi Yu, Yanhong Wei, Yanzhou Ji, Long-Qing Chen

    The misorientation angle between the preferred crystalline orientation and the temperature gradient influences both the incubation time and the average wavelength of any initial instability during the planar growth stage, as well as the dendrite growth direction and the primary dendrite arm spacing during the subsequent epitaxial growth stage. The solidification microstructure gradually changes from normal or tilted dendrites to a seaweed-like structure as the misorientation angle increases. The simulation of the initial wavelength, primary dendrite arm spacing and interface morphology are in general agreement with the experimental observations.

    更新日期:2017-12-14
  • Directed Energy Depositing a New Fe-Cr-Ni Alloy with Gradually Changing Composition with Elemental Powder Mixes and Particle Size' Effect in Fabrication Process
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-07
    Wei Li, Lei Yan, Xueyang Chen, Jingwei Zhang, Xinchang Zhang, Frank Liou

    To explore novel alloy possessing both corrosion resistance and sufficient plasticity to meet various functionality requirements in severe corrosion working environment, in this study, a new Fe-Cr-Ni based alloy with gradually changing composition was synthesized by directed energy deposition with pre-mixed elemental powder. A thin wall sample was fabricated from bottom to top layer by layer following four composition designs (Fe-16Cr-8Ni, Fe-14Cr-16Ni, Fe-12Cr-23Ni, Fe-9Cr-28Ni) to achieve the transition from ferritic phase to austenite phase. The elemental powders used in this research were characterized to analyze the shape and size distribution. The mixing enthalpy for the three elements was studied since it can impact on the deposits homogeneity. Different material characterizations were performed to examine the alloy properties. Microscopic metallography of sample was acquired to analyze the microstructure. Energy dispersive spectroscopy (EDS) analysis examined the composition in the sample. A particle size optimization idea was introduced to keep the original mixing composition. Then Vickers hardness test was done to observe the gradually changing hardness profile. Finally, the phase identification was investigated by X-ray diffraction (XRD). The results indicate that with the increasing Ni and decreasing Cr content, the Vickers hardness numbers (VHN) tend to decrease gradually. The microstructure of regions with 8% and 16% of Ni is mainly the lathy and acicular morphologies, while standard austenite morphology, cells and dendrites, were observed in the regions with 23% and 28% Ni. The XRD pattern can basically verify the metallography observation.

    更新日期:2017-12-14
  • Microstructure and Mechanical Properties of Al–Si Eutectic Alloy Modified with Al–3P Master Alloy
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-07
    Shuo Wang, Min Fu, Xiazhang Li, Jianhua Wang, Xuping Su

    The fraction of primary Si and primary α–Al in Al–Si eutectic alloy were largest after modification at 740ºC when a certain amount of Al–3P was added. The fraction of primary Si and primary α–Al in Al–Si eutectic alloy first increased and then decreased with increasing amount of Al–3P. The fraction of primary Si and primary α–Al in the Al–Si eutectic alloy was largest when the added amount of Al–3P modifier was 0.4wt.%. The fraction of primary Si and primary α–Al decreased with further increased Al–3P modifier. The size of the primary Si decreased continuously. Compared to the unmodified Al–Si eutectic alloy, the tensile strength and elongation of the alloy modified with 0.4wt.% Al–3P at 740ºC increased by 7% and 74%, respectively.

    更新日期:2017-12-14
  • Investigating the effect of picosecond laser texturing on microstructure and biofunctionalization of titanium alloy
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-07
    Zhou Yu, Guangzheng Yang, Wenjie Zhang, Jun Hu

    Laser processing technique has been an effective method to enhance the medical implant’s biocompatibility through forming specific textures on titanium alloy implant surface. In this paper, a 1064 nm pulsed picosecond laser on TC4 titanium alloy implant samples was conducted to obtain optimal parameters for well-structured textures, controllable micro-grooves and improved osteoblast adhesion and proliferation. Picosecond laser technique is generally characterized by the high flexibility and advanced properties, which could make structural features including topography quality and detailed dimensions expediently improved and changed by adjusting laser processing parameters. To obtain the optimal laser processing parameters for desired microstructures, orthogonal experiments and related SEM, EDS and SPM analysis were conducted under various laser powers, repetition frequencies, scan speeds and scan numbers. Thus, the correlation between picosecond laser processing parameters and its corresponding microstructure feature of the micro-grooves was established. In addition, the immunofluorescence detection of cell actin cytoskeleton shows that structured textures can promote cell adhesion and play an important role in cell contact guidance.

    更新日期:2017-12-14
  • Effect of high energy shot-peening on the microstructure and mechanical properties of Al5052/Ti6Al4V lap joints
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-06
    Haodong Wang, Xinjian Yuan, Kanglong Wu, Chuan Xu, Yingjun Jiao, Wang Ge, Jun Luo
    更新日期:2017-12-14
  • Constitutive equation and FEM analysis of incremental cryo-rolling of UFG AA 1050 and AA 5052
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-06
    Mohammad Sadegh Mohebbi, Abbas Akbarzadeh

    In this study, ultrafine grained aluminum sheets AA1050 and AA5052 are incrementally cryo-rolled after precooling in liquid nitrogen. Cryogenic deformation is considered as an effective approach to postpone saturation of the grain refinement by conventional severe plastic deformation. However, for a quantitative understanding of the resulted microstructure and mechanical properties, accurate values of the deformation parameters (strain, strain rate and temperature) are needed. The aim of this study is, therefore, to find values of the applied cryo-rolling parameters. As the experimental measurements of parameters such as temperature are infeasible in the thin specimens, a FEM simulation is developed and used, instead. Flow stress data at various conditions is obtained by plane strain compression and tension tests. A proper constitutive equation which is found to match well with the experiments is used to couple with the FEM model. Thermal contacts and other physical parameters are also carefully determined to achieve a reliable FEM simulation. Deformation parameters at various incremental rolling passes are obtained by this approach. Capability of the model is also verified by cryo-rolling of thick specimens at different thickness reductions. As the deformation parameters of the present experiments are defined in this study, accurate analyses of the resulted microstructures and mechanical properties can be performed.

    更新日期:2017-12-14
  • Deformation behavior of Al-Cu-Mg alloy during non-isothermal creep age forming process
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-05
    Yongqian Xu, Lihua Zhan, Minghui Huang, RuiLin Shen, Ziyao Ma, Lingzhi Xu, Kai Wang, Xun Wang

    Creep age forming process (CAF) has been developed for manufacture large aircraft components. Generally, in CAF, the component should experience heating, soaking and cooling stages. In order to acquire high precision of the creep-age formed components, the non-isothermal deformation behavior of Al-Cu-Mg alloy was investigated using the creep ageing, thermal expansion, hot tensile and creep age forming tests. During non-isothermal creep ageing process, both the elastic and thermal deformations grow in the heating stage. However, the elastic deformation drops to a certain degree and then the contraction occurs in the cooling stage. The non-isothermal creep deformation can be divided into six stages, in which the creep rate increases in the heating stage and decreases in the soaking and cooling stages. Under different applied stresses, the creep strain in the heating stage of the non-isothermal creep is about 22.28–26.86% of the total creep strain. Compared with the isothermal creep ageing process, steady-state creep rate of the non-isothermal creep ageing process is reduced. Nevertheless, total creep deformation in the non-isothermal creep ageing process is improved. Thus, the springback of the non-isothermal creep-age formed plate is smaller than that of the isothermal creep-age formed plate. It can be concluded that the creep behavior in non-isothermal conditions, particularly the heating stage, needs to be considered in CAF applications.

    更新日期:2017-12-14
  • A comprehensive investigation on temperature dependent plastic deformation behavior of one austenitic stainless steel
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-05
    Feifei Zhang, David Harsch, Niko Manopulo, Maysam Gorji, Pavel Hora

    The austenitic stainless steels are widely used in various industries due to its excellent properties. However, because of the martensitic phase transformation during the forming process, the austenitic stainless steels involve much more complex deformation behavior in comparison to the normal structure steels. Here in this paper, the deformation behavior of one austenitic stainless steel-Posco 1.4301, including the hardening behavior, yield behavior and formability behavior under different temperatures are comprehensively investigated by experimental, theoretical and finite element methods. Results show that martensitic phase transformation, which is related with temperature and strain, can greatly influence the plastic deformation behavior. This study provides a comprehensive understanding of the mechanical properties of this austenitic stainless steel and helps to better analyze the more complex deformation process in the future.

    更新日期:2017-12-14
  • Laser Weldability of Zr-2.5Nb Alloy to AISI 410 Stainless Steel with Ni Filler
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-05
    Jianyin Chen, Ahmed Khalifa, Lijue Xue, Mitch King

    The nickel interlayer improved the laser weldability of Zr-2.5Nb to AISI 410 stainless steel. The fusion zone contained a large amount of refined and tough dendritic γ-Ni(Fe, Cr) solid solution (182 ∼ 268 HV), while the brittle Zr(Fe, Cr)2 intermetallic compound (1,171 ∼ 1,460 HV), which was the main phase as the result of direct welding of Zr-2.5Nb to SS410 as well as the source responsible for the welding cracks, disappeared. Only limited quantities of Zr2(Ni, Fe), Zr7Ni10 (and/or Zr2Ni7) intermetallics were present mainly in the form of thin layers (less than 200 μm thick in total) near the fusion interface with Zr-2.5Nb. Those Zr-Ni based intermetallics showed relatively higher toughness and lower hardness (301 ∼ 497 HV) than the brittle Zr(Fe, Cr)2, which reduced the overall cracking sensitivity of the laser-weld.

    更新日期:2017-12-14
  • Visualisation and optimisation of shielding gas coverage during gas metal arc welding
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-02
    I. Bitharas, N.A. McPherson, W. McGhie, D. Roy, A.J. Moore
    更新日期:2017-12-14
  • Deflection detection and curve fitting in three-roll continuous straightening process for LSAW pipes
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-02
    Chunge Wang, Gaochao Yu, Wei Wang, Jun Zhao

    Aiming at the low efficiency of three-point mold bending straightening, a new method of three-roll continuous straightening is proposed in this paper, which is full in consideration of the geometric features and bending characteristics of LSAW pipes. Using the characteristics of the roll straightening device, a straightness detection method for large pipes is proposed just by adding a laser displacement sensor, and the calculation model for overall deflection based on local deflection is established. Based on the detected deflection data, a piecewise fitting algorithm with constraints by introducing the Kuhn-Tucker condition is proposed for straightness calculation, and a simple polynomial fitting method with fourth order is determined for the calculation of curvature and straightening moment. Further, using the semi-automatic experimental prototype for small pipes, the deflection detection experiments show that the overall deflection error is less than 3.5% compared with that of CMM, the piecewise fitting results show that the ideal order of the mid-segment is 10-th, and the three-roll continuous straightening experiments show that the novel method can correct the straightness to less than 0.2%, meeting the standard requirements.

    更新日期:2017-12-14
  • Single Scan Track Analyses on Aluminium based Powders
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-02
    Alberta Aversa, Mandanà Moshiri, Erica Librera, Mehdi Hadi, Giulio Marchese, Diego Manfredi, Massimo Lorusso, Flaviana Calignano, Sara Biamino, Mariangela Lombardi, Matteo Pavese
    更新日期:2017-12-14
  • 更新日期:2017-12-14
  • Simulation and experimental research of the free bending process of a spatial tube
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-02
    Xunzhong Guo, Yannan Ma, Wenliang Chen, Hao Xiong, Yong Xu, Ali Abd El-Aty, Kai Jin

    The free bending technology is regarded as a promising fabricating technology in the recent years. Due to characteristics of complex product shape and dieless forming, this technology arises more and more attention recently. Firstly, this paper analyzed movement track of bending die based on the principle of free bending technology. Then, distribution characteristics of equivalent stress and strain on tube and bending die during different stages of the free bending process were analyzed. Afterwards, this paper studied the influence law of clearance between tube and bending die, fillet radius of guider, feeding speed on the tube free bending quality. Relationship between eccentricity U of bending die and bending radius R of tube relates to the bending program directly. In this paper, U-R relationship was obtained by finite element simulation to verify the accuracy of the built model. FE simulation and bending experiments were conducted based on the research results. The result revealed that dimension of the bent spatial tube was close to the CAD model and proved the reliability of U-R relationship. Deviation of the bending radius and bending angle is supposed to occur due to springback after forming.

    更新日期:2017-12-14
  • Assessment on abrasiveness of high chromium cast iron material on the wear performance of PCBN cutting tools in dry machining
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-02
    Ling Chen, Jan-Eric Stahl, Wu Zhao, Jinming Zhou

    Polycrystalline Cubic Boron Nitride (PCBN) has been considered as the main cutting tool material for hard turning, which has the comparable surface finish quality as grinding, and high efficiency, economical technology in production. It is well known that the abrasiveness of the workpiece have the very important role of the machinability of the materials. Therefore, the tool wear of the PCBN insert correlates with abrasiveness of the materials very much. In the presented paper, the influence of the micro hardness distribution is used to explain the wear mechanism in machining of the high abrasive materials and proposed a model to predict the abrasiveness. The work material is high chromium cast iron and cutting tool material is PCBN. Abrasiveness are evaluated from the micro hardness distribution by nanoindentation for the distinguish microstructure with hardness. The mapping image of the micro hardness showed the matched features with microstructure images from the scanning electron microscope (SEM). The different chemical composition groups are presented as three heat treatment conditions in experiments, which are as-cast, annealed and hardened. Based on the hardness distribution, this paper presented a model to evaluate the abrasiveness index of the material. The high performance machining is done on six material. The wear mechanism is abrasion in tool wear dominantly and flank wear showed the linear relationship with abrasiveness index. The abrasive wear on the cutting edge suggests that sliding and chipping are the main wear modes which is caused by the combination effect of carbides and matrix. The four mechanisms of diffusion, chemical, abrasive and micro chipping are happening in the tool wear of hard turning. In the dry machining by PCBN insert, abrasiveness is correlated with abrasive and chipping very much and accelerated the crater wear in machining. Abrasiveness index of the material has ability to predict wear performance in dry machining of HCWCI materials by PCBN inserts. The application of the abrasiveness is a potential parameter of machinability to improve the machining efficiency and reduce the cost of machining.

    更新日期:2017-12-14
  • Pressure-assisted infiltration of molten metals into non-rigid, porous carbon fibre structures
    J. Mater. Process. Tech. (IF 3.147) Pub Date : 2017-12-01
    H. Constantin, L. Harper, A.R. Kennedy

    Mercury intrusion porosimetry has been conducted on a range of non-rigid, porous carbon fibre structures. Comparison with data from gas pressure infiltration experiments in a molten Al-Si alloy shows it to be a useful tool in determining the pressure required to produce Al metal matrix composites with low levels of porosity. Whilst for non-rigid fibre preforms, as studied here, it is difficult to pin-point every aspect of the infiltration process, the method does give an indication of critical aspects of the infiltration behaviour. Preforms made from loose and spread tow can be fully infiltrated at relatively low pressures (12 bar) and although metal can fill the spaces between fibre bundles within textile-based preforms at low pressures, densely-packed bundles are only infiltrated at higher pressures, usually in excess of 50 bar. Mercury intrusion porosimetry could provide a valuable and simple tool in the design of fibre-reinforced metal matrix composites with optimised structures that are easy to manufacture.

    更新日期:2017-12-14
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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