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  • Effect of Initial Orientation on Corrosion Behavior of AZ80 Magnesium Alloy in Simulated Body Fluid
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-22
    Tao Zhu, Xinghua Gong, Ying Xiong, Xiaxia Hu

    Abstract Three different orientation specimens (P-ND30, P-ND60 and P-TD) prepared from the rolled AZ80 magnesium alloy plates were immersed in simulated body fluid (SBF) for 384 h. Electrochemical impedance spectroscopy (EIS) tests were measured at 24 h, 96 h, 192 h, 288 h, and 384 h during immersion. The corrosion morphology and chemical composition of the three orientation specimens were investigated using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). X-ray diffractometer (XRD) was used to evaluate the phase composition of the surface of the specimen at different immersion stages. The results indicated that the P-ND30 and P-ND60 specimens had similar corrosion behavior. The P-TD specimen showed the best corrosion resistance. A degradation evolution model was established, and the effect of initial orientation on corrosion behavior was discussed. Graphic Abstract

    更新日期:2020-01-23
  • Investigation on the Effect of Stirring Process Parameters on the Dispersion of SiC Particles Inside Melting Crucible
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-21
    Vishal R. Mehta, Mayur P. Sutaria

    Abstract Stirring based liquid metal processing is the widely explored process by researchers for the production of metal matrix composites (MMCs). The dispersion of reinforcement particles is the major challenge in the process. The stirring process parameters govern the dispersion of reinforcement particles in MMCs. The important stirring process parameters are stirring speed, stirrer geometry, stirrer position, and stirring time. In the literature, research works are reported, where the effect of such parameters on the dispersion of particles was investigated either by analyzing flow field using computational methods (assuming constant fluid properties) or by sectioning the casted samples. In cast condition, the dispersion of particles is also influenced by the solidification phenomena. The aim of the present work is to investigate the significance and the effect of stirrer geometry, stirrer position and stirring speed on the dispersion of reinforcement particles inside melting crucible, during the stirring. Aluminium alloy LM25 was used as the matrix material and silicon carbide (SiC) particles having mean size 37.58 microns (d50 value) were used as the reinforcement phases. Samples of the composite slurry during the stirring process were dragged using a quartz tube at three levels inside crucible and microstructure analysis was carried out. Number density (ND) and inter particle distance were evaluated for parameter combinations. The uniform dispersion of SiC particles was observed at 45° stirrer blade angle, 400 rpm stirring speed and 40 mm stirrer position. And, significance order of individual parameter was observed as stirring speed < stirrer position < stirrer blade angle. Graphic Abstract

    更新日期:2020-01-22
  • Current Review on the Research Status of Cemented Carbide Brazing: Filler Materials and Mechanical Properties
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-18
    Xiaohui Yin, Qunshuang Ma, Bing Cui, Lei Zhang, Xingyan Xue, Sujuan Zhong, Dong Xu

    Abstract Cemented carbides have been widely applied in cutting tools and wear-resistant components due to their ultrahigh hardness and good wear resistance. However, the disadvantages of limited impact toughness and high cost have restricted their further application. Consequently, cemented carbides are usually joining with ductile steels to combine the advantages of both. Among various materials joining technologies, brazing have been an effective method to achieve high quality dissimilar cemented carbide joints. In this paper, the research status of cemented carbide brazing is reviewed. The materials utilized as brazing filler metal in cemented carbide brazing joints are summarized in detail. Researchers have done lots of works utilizing Cu based and Ag based brazing filler metals which are the most commonly used interlayers in brazed joints of cemented carbide and ductile steel. The effects of different filler metal on wettability, microstructure, phase constitution and mechanical properties of brazed cemented carbides joints are analysed. Besides, a series of newly developed brazing filler material such as nickel-based high temperature brazing filler metal, amorphous brazing filler metal and high entropy alloy brazing filler materials are also involved. These newly developed brazing filler metals have shown great potential in fabricating high quality joints. Finally, the current issues of cemented carbide brazing are reviewed and the develop trend is predicted. Graphic Abstract

    更新日期:2020-01-21
  • Evaluation of Palm Kernel Cake Powder ( Elaeis guineensis Jacq. ) as Corrosion Inhibitor for Carbon Steel in Acidic Media
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-18
    A. M. Santos, I. P. Aquino, F. Cotting, I. V. Aoki, H. G. de Melo, V. R. Capelossi

    Abstract This work aims to investigate the possible use of the palm kernel cake powder (Elaeis guineensis Jacq.) as corrosion inhibitor for ASTM 1020 carbon steel in acidic media (0.5 mol L−1 HCl). The investigation was carried out using electrochemical impedance spectroscopy (EIS), polarization curves, gravimetric technique and scanning vibrating electrode technique (SVET). Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were employed as chemical and surface characterization techniques, respectively. The results of the EIS and gravimetric tests showed that the substance acts as an effective corrosion inhibitor and inhibition efficiency (IE) increases according with the increase of the corrosion inhibitor concentration in the aggressive medium. The highest IE of 87% was obtained for the highest corrosion inhibitor concentration used (1.77 g/L). The polarization curves revealed a mixed inhibitor. The adsorption of the studied inhibitor on carbon steel surface obeyed Langmuir isotherm. The SVET measurements did not reveal anodic or cathodic activities in the substrate surface in the presence of the inhibitor, revealing that the corrosion inhibitor was able to block both reactions. FTIR analyses identified in the powder the presence of hydroxyl group, aromatic rings, nitrogen and oxygen in such groups as amines and oleaginous acid, which can be responsible for the inhibitory properties of the whole material. SEM analyses showed that the corrosion process was retarded when the inhibitor was added to electrolyte. The results indicate that the powder of palm kernel cake is promising for use as corrosion inhibition purpose for carbon steel in acidic media. Graphic Abstract

    更新日期:2020-01-21
  • Incorporation of SiC Ceramic Nanoparticles into the Aluminum Matrix by a Novel Method: Production of a Metal Matrix Composite
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-17
    R. Taherzadeh Mousavian, S. Behnamfard, A. Heidarzadeh, K. Taherkhani, R. Azari Khosroshahi, D. Brabazon

    Abstract SiC ceramic nanoparticles were incorporated into the A356 aluminum matrix with different compositions using a combination of stir casting and semisolid extrusion. The microstructure and mechanical properties of the produced nanocomposites were evaluated. The results showed that the presence of Nickel acts as an appropriate metallic carrier for SiC nanoparticles, which causes uniform dispersion and spherical grains. Consequently, the coexistence of SiC nanoparticles and Nickel resulted in UTS of above 304 MPa and elongation of 5.8%. However, the addition of Titanium caused the formation of flake-like intermetallics, which decreased the elongation of the nanocomposites. The method introduced in this study for the incorporation of SiC ceramic nanoparticles can be used as a promising process instead of conventional methods, which are expensive and time-consuming. Graphic Abstract

    更新日期:2020-01-17
  • Microstructure, Mechanical Properties and Fracture Behavior of Magnesium/Steel Bimetal Using Compound Casting Assisted with Hot-Dip Aluminizing
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-16
    Wenming Jiang, Haixiao Jiang, Guangyu Li, Feng Guan, Junwen Zhu, Zitian Fan

    Abstract In this work, microstructure, mechanical properties and fracture behavior of the magnesium/steel bimetal using compound casting assisted with hot-dip aluminizing were investigated, and the interface bonding mechanism of the magnesium/steel bimetal were also analyzed. The results indicate that the magnesium/steel bimetal obtained without hot-dip aluminizing had larger gaps through the whole interface without reaction layers between magnesium and steel, leading to a poor mechanical bonding. After the steel substrate was hot-dip aluminized, an intermetallic layer along with an Al topcoat layer were formed on the surface of the steel substrate, and the intermetallic layer was constituted by Fe2Al5, τ10-Al9Fe4Si3, FeAl3 and τ6-Al4.5FeSi phases. In the case of the magnesium/steel bimetal obtained with hot-dip aluminizing, a compact and uniform interface layer with an average thickness of about 17 μm that consisted of Fe2Al5, τ10-Al9Fe4Si3, FeAl3 and Al12Mg17 intermetallic compounds was formed between the magnesium and the steel, obtaining a superior metallurgical bonding. The interface layer had much higher nano-hardnesses compared to the magnesium and steel matrixes, and its average nano-hardness was up to 11.1 GPa, while there were respectively 1.1 and 4.2 GPa for the magnesium and steel matrixes. The shear strength of the magnesium/steel bimetal with hot-dip aluminizing reached to 23.3 MPa, which increased by 8.59 times than that of the composites without hot-dip aluminizing. The fracture of the magnesium/steel bimetal with hot-dip aluminizing represented a brittle fracture nature, initiating from the interface layer. Graphic Abstract

    更新日期:2020-01-16
  • Characterization of Ti–Al Intermetallic Synthesized by Mechanical Alloying Process
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-16
    Manoj Kumar Yadav, Arshad Noor Siddiquee, Zahid A. Khan

    Mechanical alloying (MA) of Al60Ti40 (wt%) has been successfully done by using a planetary ball mill having mixed balls of 5 mm and 15 mm diameter to refine the crystallite size of the elemental powder and to get the new MAed phase of AlTi. The microstructural and morphological analysis of elemental as well as the processed powder was done with help of Scanning Electron Microscope and X-Ray diffraction technique. Mechanical alloying of elemental Al and Ti resulted in the formation of AlTi phases with the reflection of α-Ti3Al and TiAl3. The average particle size was reduced around 7 times after 60 h of milling. The mean crystallite size of MAed powder was also reduced up to 85 nm after 60 h of mechanical alloying under controlled conditions.

    更新日期:2020-01-16
  • Microstructure, Texture Characteristics, Mechanical and Bio-Corrosion Properties of High Strain Rate Rolled Mg–Zn–Sr Alloys
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-13
    Hongge Yan, Xiaole Gong, Jihua Chen, Meixin Cheng

    Abstract Microstructure, texture characteristics, mechanical and bio-corrosion properties of the Mg–5Zn–xSr alloys (x = 0, 0.2, 0.6, 1.0) prepared by high strain rate rolling are carefully studied. A low level of Sr addition enhances dynamic precipitation of nano-scale MgZn2 particles in the as-rolled Mg–5Zn alloy, with 0.6%Sr showing the maximum efficiency. These high-density MgZn2 particles can pin grain boundaries of dynamic recrystallization grains and inhibit their growth. A low level of Sr addition (≤ 0.6%) enhances the (0002) basal texture, but 1.0%Sr is just the reverse. The as-rolled Mg–5Zn–0.6Sr alloy exhibits the best combination of ultimate tensile strength (359 MPa) and elongation to rupture (20%). The high strength can be attributable to a reduced grain size, precipitation and basal texture strengthening. The Mg–5Zn–xSr alloys exhibit excellent bio-corrosion resistance, but a minor Sr addition cannot bring about further bio-corrosion resistance improvement due to the multiple actions of grain size, DRX degree, dynamic precipitates and texture characteristics. The 0.6%Sr addition can greatly improve the strength of the as-rolled alloy at no expense of bio-corrosion resistance. Graphic Abstract

    更新日期:2020-01-13
  • Phase Transformation Modeling for Hypo Peritectic Steel in Continuous Cooling
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-13
    Jun-hyun Jo, Kyung-woo Yi

    Abstract Phase change of steel during cooling affects the slab qualities in continuous casting. Especially, crack susceptibility of hypo peritectic steel is high because large volume shrinkage occurs by peritectic phase transformation during solidification and cooling. In continuous cooling, phase change is different from the behaviors under the equilibrium condition, such as undercooling and extend of peritectic reaction, etc. Therefore, we develop a new phase change model considering thermodynamics, empirical equations, and carbon diffusion in each phase to predict phase change behavior during continuous cooling. In this model, phase change of hypo peritectic steel comprises 5 stages until all phases become the γ phase. The velocities of the δ/γ interface and phase fractions during cooling are calculated according to cooling rate, undercooling of the γ phase, and carbon contents. The results show that if solidification ends by the δ phase during dTp, the γ phase is formed by massive transformation. On the contrary, if peritectic reaction starts with liquid, the γ phase is formed and grows by diffusional transformation. In latter case, massive transformation of remaining δ phase can occur with high undercooling or very fast cooling rates. This analysis shows that there are several different paths depending on carbon contents of hypo peritectic steels. Graphic Abstract Phase change of hypo peritectic steel.

    更新日期:2020-01-13
  • Retardation of Grain Growth in Al 3003 Nanocomposite Weldment Using ARB Filler Metal
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-10
    K. R. Ramkumar, S. Natarajan

    Abstract This research demonstrates the feasibility of filler rod fabrication to develop nanocomposite weldment to enhance the joint strength via ARB technique. Al 3003 alloys were joined through GTAW by melting fabricated nanocomposite filler metal. TiO2 nanoparticles were chosen as reinforcement from 0 to 3 wt%. Roll bonding is desired owing to the proper distribution of TiO2 particles. SEM depicted the distribution of reinforcement particles in the grain boundaries. TEM disclosed the uniformity in particulates distribution, peening of dislocation and strain fields in 12 wt% TiO2 reinforced nanocomposite weldment. EBSD portrayed the grain refinement occurred in the weld zone due to reinforcement addition. The improvement in impact and bending strength were due to excellent bonding between the Al and reinforcement particles and excellent load transfer ability provided by reinforcement particles. Graphic Abstract

    更新日期:2020-01-11
  • Effect of Copper-Based Spring Alloy Selection on Arc Erosion of Electrical Contacts in a Miniature Electrical Switch
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-10
    Seulki Hwang, Daesup Hwang, Hani Baek, Chansun Shin

    A spring beam in a miniature electrical switch enables the two electrical contacts to either close or separate and supplies both current and necessary contact pressure between the contacts. Arc erosion and material transfer between the contacts occur, and those aspects depend on various parameters including the kinematics of the contacts. Therefore, the mechanical properties of the spring beam will affect the arc erosion and material transfer, but this topic has not been well studied. In this study, the material transfer phenomena between two AgCu contacts attached to a spring beam made of three different copper-based strip alloys were investigated after 30,000 switching operations under 12 V and 9 A in a direct-current resistive load circuit. For spring beams made of beryllium copper (BeCu) and titanium copper (TiCu) alloy, the material transfer occurred from the cathode to the anode. However, an opposite material transfer occurred for a spring beam made of Corson-type (CuNiSi) alloy. The make- and break-arc voltage waveforms were analyzed, and the results showed that the changes in arcing behaviors depend on the spring beam material. The properties of the spring beam materials responsible for the changed arcing behaviors are discussed and their relationship with the observed contact arc erosion and material transfer is analyzed.

    更新日期:2020-01-11
  • Calibration of Laser Penetration Depth and Absorptivity in Finite Element Method Based Modeling of Powder Bed Fusion Melt Pools
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-10
    Jaewoong Kim, Seulbi Lee, Jae-Keun Hong, Namhyun Kang, Yoon Suk Choi

    Abstract A systematic parametric study was conducted using thermal finite element method simulations in order to calibrate the laser penetration depth and absorptivity as a function of the laser power and scan speed for single tracks of Alloy 718 processed by laser powder bed fusion. A methodology was developed to calibrate both laser penetration depth and absorptivity using an algorithm proposed. Calibrated laser penetration depths and absorptivities captured experimentally observed variations of the melt pool depth and width with the laser power and scan speed, and showed strong correlations with a modified energy density, which is the laser power normalized by a square root of the scan speed (W/(m/s)1/2). The result indicated that the laser penetration depth and absorptivity heavily influence the determination of the melt pool depth and width, respectively. Variations of calibrated laser penetration depths and absorptivities with the laser power and scan speed reasonably depicted physical phenomena related with how incident laser beam interacts with the melt pool under different input energy densities, and were in quantitative agreement with those calculated from an analytical model and observed from the experiment. Graphic Abstract

    更新日期:2020-01-11
  • Performance of Novel TWO-CAP (Thin-Walled Open Channel Angular Pressing) Method on AA5083
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-10
    Mehmet Şahbaz, Aykut Kentli, Hasan Kaya

    Abstract Newly developed severe plastic deformation (SPD) method TWO-CAP was applied to AA5083 to increase its mechanical properties. The method was developed to obtain the structural beams which have a thin-walled open-cross section area in high strength to weight ratio. During the TWO-CAP process, the annealed U-profile specimens will be pressed along the specifically designed die channel with the help of the hydraulic press machine. After the expansion and narrowing processes, the specimen leaves the die with initial dimensions at the end of each pass. Therefore, the material gains strength, hardness, and toughness while the microstructure of the material was improved as a result of the SPD. In order to determine the effect of the TWO-CAP on the mechanical properties of the material, the hardness and tension tests were carried out on the all passed specimens. Also, the characteristic investigations were performed on the specimens by using optical microscopy, SEM–EDS, and XRD analyses. Graphic Abstract

    更新日期:2020-01-11
  • Comparative Modeling of Power Hardening Micro-scale Metallic Plates Based on Lower and Higher-Order Strain Gradient Plasticity Theories
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-09
    Amer Darvishvand, Asghar Zajkani

    Abstract Present study investigates a comparative study of lower and higher-order strain gradient plasticity (SGP) theories involving the size-dependent micromechanically flexural behaviors of crystalline thin plates. The investigation includes the Mechanism-Based and the Chen–Wang SGP models established on the Taylor dislocation hardening by evoking the statistically stored dislocations and geometrically necessary dislocations. In addition, these models are conjugated with a multiple plastic work-hardening law proposed for the microstructural applications of the SGP. An analytical approach based on energy minimizing method is used for obtaining deflection values in terms of the length scale, exponent of the work-hardening and the tangential module. The obtained results indicate a meaningful dependence of the deflections to the length scale, plastic work hardening and other parameters as well. Graphic Abstract

    更新日期:2020-01-11
  • Correction to: Effect of Cu Contents on Nanocluster Formation and Two-Step Aging Behavior in Al–Mg–Si Alloys
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-09
    MinYoung Song, InSu Kim, JaeHwang Kim, SungKil Hong

    In the original publication, the fourth author name was published incorrectly. The correct author name is given in this Correction.

    更新日期:2020-01-09
  • Numerical and Experimental Analysis of Rotating Backward Extrusion as a New SPD Process
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-09
    Xin Che, Qiang Wang, Beibei Dong, Mu Meng, Zhiming Zhang

    Rotating backward extrusion (RBE) as a new severe plastic deformation technique is a continuous process to produce cylindrical tubes with fine grains and superior properties. In this study, the RBE process with an open punch was applied to the AZ80 alloy at 653 K, and the deformation mechanisms and the microstructure evolution were examined by the finite element method (FEM) and thermal simulation experiment. The results showed that the effective strain of the RBE process was higher than that of the conventional backward extrusion (CBE) process, and the strain increased with revolutions increasing. The strain improvement of the RBE process was related to the large cumulative plastic deformation imposed by the continuous rotation of the open punch. Furthermore, the extrusion load was reduced significantly in the RBE process comparing with the CBE process, due to the change of friction stress and stress state of the materials. And the maximum load reduction of the FEM and experiment was 47.33% and 31.6%, respectively. The average grain size of the RBE sample could be reduced by up to 90% in the region A at 30 N compared with the CBE sample. The maximum increase in microhardness of the RBE sample relative to the CBE sample was 23% at 30 N in the region A. Therefore, the grain refinement and mechanical properties of the materials can be substantially improved by the RBE process.

    更新日期:2020-01-09
  • Effect of Mn Modification on Microstructure and Mechanical Properties of Magnesium Alloy with Low Gd Content
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-08
    Dongdong Gu, Jian Peng, Jiawen Wang, Fusheng Pan

    The evolution of microstructure and mechanical properties of the dilute Mg–Gd alloy with Mn modification were investigated systematically in this paper. The results show that the combination of Mn and different processing states could adjust the solid solubility of Gd in the Mg matrix, thereby changing the morphology of the second phases and improving the properties of the alloy. With the addition of 0.8 wt% Mn into the Mg–4Gd alloy, the atomic utilization ratio of Gd atoms decreases from 61.5 to 51.8% during the water-cooling casting process, but it increases from 73.8 to 81.0% during homogenization treatment and increases from 72.3 to 84.1% during hot extrusion. Thus, the mean diameter of granular phases of the Mg–4Gd alloy is larger than that of Mg–4Gd–0.8Mn alloy after the isothermal heat treatment. The Mn addition has little effect on the Hall–Petch constant KY and KH of Mg–4Gd alloy, but improves the σ0 value significantly due to the increase of the atomic utilization ratio of Gd atoms. Mn element can improve the mechanical properties of Mg–4Gd alloy, and the increase of yield strength and ductility of as-extruded Mg–4Gd–0.8Mn alloy is mainly attributed to grain refinement and the decrease of the texture intensity.

    更新日期:2020-01-08
  • Improvement in Mechanical Properties of Rolled AZ31 Alloy Through Combined Addition of Ca and Gd
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-08
    Jongbin Go, Jong Un Lee, Byoung Gi Moon, Jonghun Yoon, Sung Hyuk Park

    Abstract In this study, the effects of the combined addition of Ca and Gd on the microstructure and mechanical properties of rolled Mg alloys are investigated by the addition of 0.5 wt% Ca and 0.5 wt% Gd to a commercial AZ31 alloy. The combined addition of Ca and Gd leads to the formation of undissolved second phases such as Al2Ca and Al2Gd, which promote dynamic recrystallization during rolling via the particle-stimulated nucleation phenomenon. As a result, the rolled AZ31–0.5Ca–0.5Gd (wt%) (AZXG3100) alloy shows a finer recrystallized grain structure than the rolled AZ31 alloy; the average grain size of the former (11.9 µm) is considerably smaller than that of the latter (22.4 µm). The combined addition of Ca and Gd improves the tensile yield strength of the rolled material from 131 to 144 MPa, which is attributed mainly to the combined effects of Hall–Petch hardening enhanced by grain refinement and dispersion hardening induced by the undissolved particles. The tensile elongation of the rolled material also increases from 14.6 to 18.3% upon the combined addition of Ca and Gd, because the activation of twinning during tension is less pronounced in the rolled AZXG3100 alloy owing to its smaller grain size. These results demonstrate that the combined addition of Ca and Gd simultaneously improves the tensile strength and ductility of the rolled AZ31 alloy. Graphic Abstract Combined addition of Ca and Gd to rolled AZ31 alloy.

    更新日期:2020-01-08
  • Strength of Thixoformed A319 Alloy at Elevated Temperature
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-08
    A. M. Aziz, M. Z. Omar, Z. Sajuri

    Abstract When alloys are exposed to elevated temperatures they experience a decrement in their mechanical properties that leads to material failure. However, the use of thixoforming, an alternative metal processing method, could enhance mechanical properties by minimising the defects that exist in as-received alloys. Therefore, this study aimed to determine the tensile strength of thixoformed A319 under elevated temperatures by taking into account its intended use in vehicle cylinder head components. Thixoformed A319 was compared with as-received alloy manufactured by permanent mould casting. The cooling slope method was used to prepare the feedstock for thixoforming. The feedstock was reheated by induction heating until it reached 574 °C and was then formed in a mould. Afterwards, the as-received and thixoformed samples underwent T6 heat treatment. The resulting samples were characterised by using optical microscopy, scanning electron microscopy equipped with energy dispersive X-ray, X-ray diffraction analysis and a tensile test. Elevated temperature tensile tests were performed at 250 °C, in line with the temperature condition experienced by cylinder head components during operation. The ultimate tensile strength of the thixoformed samples was 30% higher than that of the as-received samples under elevated temperatures. Also, the analyses of the fracture surfaces showed that porosity, intermetallic compounds and impurities were amongst the failure factors for both alloys. Graphic Abstract

    更新日期:2020-01-08
  • Thermodynamic Prediction of Phase Formation in Ni–P Alloy System During Mechanical Alloying: Comparison with Electroless Plating Technique
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-06
    M. Imani, E. Dastanpoor, M. H. Enayati, A. K. Basak

    Abstract Mechanical alloying (MA) of Ni and P powders containing 20 and 12 wt% P was investigated. The structural changes of alloys during mechanical alloying were studied by X-ray diffractometry and transmission electron microscopy. The results showed that the interdiffusion of Ni and P elements during MA of Ni80P20 alloy leads to the development of Ni12P5 and Ni2P intermetallic compounds. However MA of the Ni88P12 alloy leads to the formation of an intermetallic compound (Ni3P) and a solid solution (α-Ni) as well as partially amorphous structure. Intermediate annealing of MAed Ni88P12 alloy does not promote the formation of fully amorphous structure. Furthermore, thermodynamic analysis using the Miedema’s semi-empirical model showed that the intermetallic phases are the most stable phases in Ni88P12 and Ni80P20 alloys during MA. Graphic abstract

    更新日期:2020-01-06
  • Characterization of Co–Cr–Fe–Mn–Ni High-Entropy Alloy Thin Films Synthesized by Pulse Electrodeposition: Part 2: Effect of Pulse Electrodeposition Parameters on the Wettability and Corrosion Resistance
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-06
    Fateme Yoosefan, Ali Ashrafi, Seyed Mahmoud Monir vaghefi

    Abstract Co–Cr–Fe–Mn–Ni high-entropy alloy thin films were synthesized by pulse electrochemical deposition method. The films were co-deposited in an electrolyte based on a DMF-CH3CN organic system consisting of Co, Cr, Fe, Mn, and Ni cations via the pulse electrodeposition method at 2500 and 5000 Hz frequencies, as well as 50% and 60% duty cycles. The GXRD patterns indicated that films consisted of a single face-centered-cubic structure. The effect of pulsed electrodeposition parameters on wettability and corrosion resistance of coatings was investigated as well. The results of the hydrophobic/hydrophilic test showed that all coatings were completely hydrophilic; the largest wettability angle is for the prepared film at a duty cycle of 50% in frequency of 5000 Hz (56°). The potentiodynamic polarization test results showed that same sample with a corrosion density of 0.067 μA/cm2, improved the corrosion resistance of the substrate due to the superhydrophilic properties of those by about 34 times, and therefore, was chosen as optimal conditions. Also, it was shown that none of the samples were sensitive to pitting corrosion. The results of the EIS test showed an outstanding performance of coatings in improving corrosion resistance compared to similar alloy samples, with a conservation efficiency of about 95%. In addition, it enables the evaluation of continuous changes in the metal-coating system. In such conditions, prepared film at 50% duty cycle in frequency of 5000 Hz improved the corrosion resistance of the substrate by about 40 times. Graphic Abstract

    更新日期:2020-01-06
  • Microstructure and Tensile Properties of Ferritic Lightweight Steel Produced by Twin-Roll Casting
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-06-12
    Yunik Kwon, Ji Hyun Hwang, Hee Chae Choi, T. T. T. Trang, Byoungkoo Kim, A. Zargaran, Nack J. Kim

    Ferritic Fe–8Al–5Mn–0.1Nb–0.1C lightweight steel has been produced by twin-roll casting (TRC) process. The microstructures, in as-cast condition and during subsequent thermomechanical treatments, and tensile properties of the steel have been investigated and compared to those of the similar steel produced with conventional ingot casting (IC). TRC significantly refines the microstructure of the steel in as-cast condition, with a formation of NbC and κ-carbide particles within matrix and along grain boundaries. NbC particles inhibit the grain coarsening during subsequent homogenization treatment, while κ-carbide particles promote recrystallization during final annealing by particle-stimulated nucleation mechanism. Tensile properties of the TRC steel are comparable to those of the IC steel; however, such properties of the TRC steel have been achieved under a much smaller number of processing steps, making TRC as an ideal alternative for the production of ferritic lightweight steels.

    更新日期:2020-01-06
  • Anelastic and Microplastic Damping of an Mg–Zn–Y–Al Alloy
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-06-04
    Diqing Wan, Jiajun Hu, Yinglin Hu, Houbin Wang

    Abstract In this study, the Mg97Zn1Y2–Al alloy was selected as a high damping material, anelastic and microplastic damping were analyzed by studying strain amplitude-dependent damping curves of the alloy. The C1 and C2 values of the Granato–Lücke (G–L) model, the theoretical basis of anelastic damping, can be calculated for each alloy, then, the corresponding numbers of strong and weak pinners are deduced. However, since the occurrence of microplastic damping in a high strain amplitude cannot be explained by the G–L model, a new microplastic damping theory was introduced, by comparing the activation volume of the material dislocation slip, the microplastic damping capacity of the Mg97Zn1Y2–xwt%Al (x = 0.3, 1, 3) alloys at the microplastic stage are compared. The elastic and plastic deformation of the materials could be sensitively reflected by studying the damping behavior of these two stages.

    更新日期:2020-01-06
  • Experimental Investigation on the Effect of Ag Addition on Ternary Lead Free Solder Alloy –Sn–0.5Cu–3Bi
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-06-04
    S. Jayesh, Jacob Elias

    Lead cannot be used in the solder material anymore due to environmental legislations which is related to the inherent toxicity of lead. This paper investigates the effect of silver (Ag) addition on the melting behavior, microstructure, and microhardness of Ternary lead free solder alloy Sn–0.5Cu–3Bi. The contact angle between Sn–0.5Cu–3Bi and Cu-substrate were also analyzed. Samples with different Ag percentages (0, 0.25, 0.5, 0.75 and 1.0 wt%) in Sn–0.5Cu–3Bi were prepared using an induction furnace, annealing furnace with argon gas. Tests were conducted for melting temperature using TG–DTA analysis, chemical composition using ICP–OES, Hardness using Vickers’s hardness tester and the microstructure using Field emission scanning electron microscopy. The obtained results were thoroughly analyzed. The results show that the Ag addition has striking positive effects on enhancing the properties of the base solder alloy. Melting point is found to be decreasing with the increase in Ag content. Hardness and contact angle were improved with the addition of Ag. The microstructure observations revealed that the Ag was uniformly distributed on the surface of the solder matrix. The recommended content of the Ag to be added into the Sn–0.5Cu–3Bi solder alloy is 1.0 wt%. With the observed better properties it can be considered as the potential alternative to lead–tin alloy.

    更新日期:2020-01-06
  • Evaluating Corrosion Resistance of Additive-Manufactured Ti–6Al–4V Using Electrochemical Critical Localized Corrosion Temperature
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-11-07
    Jae-Bong Lee, Dong-il Seo, Hyun Young Chang

    A new concept to evaluate the localized corrosion resistance of stacked Ti alloys such as additive-manufactured (AM) Ti–6Al–4V alloy is proposed. Crevice corrosion of subtractive-manufactured (SM) Ti–6Al–4V occurred on the surface beneath the crevice former, whereas localized corrosion of the AM alloy occurred in any vulnerable site irrespective of the crevice assembly. The electrochemical critical localized corrosion temperature (E-CLCT) was measured to evaluate the resistance of AM Ti–6Al–4V alloys to localized corrosion. The results showed that the localized corrosion of AM Ti–6Al–4V was attributable to the anisotropy and microstructure that resulted from rapid cooling, which were completely different from the anisotropy and microstructure of SM Ti–6Al–4V. The optimum applied potential of AM Ti–6Al–4V in 25 wt% NaCl aqueous solution was deduced. The E-CLCT provides a useful criterion for determining the resistance of AM Ti alloys to localized corrosion and for comparing their resistances.

    更新日期:2020-01-06
  • Densification and Magnetic Properties of Injection Molded Gas- and Water-Atomized Fe–Si Alloys and Effect of Fe-10.2 wt% P Addition
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-06-24
    Da Seul Shin, Joo Won Oh, Im Doo Jung, Hwi Jun Kim, Min Woo Lee, Goo Won Noh, Woo Seok Yang, Seong Jin Park

    Abstract This study investigated the effect of the water and gas atomized Fe–Si powders on the densification behavior and consequential magnetic properties of the sintered soft magnetic alloys by metal injection molding. The water and gas atomized Fe–Si powders were used to fabricate the injection molded parts with the same solids loading of 58 vol% to analyze the inherent characteristics of each powder admixture. Dilatometry analysis was performed to understand the densification behavior of the water and gas atomized powders, and the master sintering curve model was developed to quantify the differences. The results showed that a significant amount of oxides in the water atomized powder reduced not only the densification but also the overall magnetic properties. The gas atomized sample exhibited the higher sintered density than the water atomized sample, and consequentially higher magnetic induction was obtained. The lower core loss, lower coercivity, and the higher permeability were also obtained from the gas atomized sample with the relatively low oxide level and large grain size. In addition, Fe-10.2 wt% P (Fe-17 at% P) powder was added to activate the liquid phase sintering, as a method to overcome the weakness of poor densification of the Fe–Si powders. Although both the water and gas atomized samples achieved near-full density with Fe-10.2 wt% P, the gas atomized sample yielded superior magnetic properties as compared with the water atomized sample. Graphical Abstract

    更新日期:2020-01-06
  • Comparative Hot Workability Characteristics of an Al–Si/SiCp Aluminium Matrix Composite Hybrid Reinforced with Various TiB 2 Additions
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-04
    Xinrong Chen, Zhiming Xu, Dingfa Fu, Hui Zhang, Jie Teng, Fulin Jiang

    Abstract Hot compression tests were conducted on Al–Si/SiCp + TiB2 hybrid aluminium matrix composites with various TiB2 contents at temperatures from 350 to 500 °C and strain rates from 0.001 to 1 s−1. The hot workability characteristics and deformation mechanisms were investigated by combining constitutive equations, processing maps and microstructural observations through scanning electron microscopy and transmission electron microscopy measurements. The results showed that there were small differences in the peak stresses when the contents of TiB2 were 3% and 5%, while the peak stress increased when the content of TiB2 reached 8%. The contents of TiB2 had little influence on the activation energy but affected the processing maps to a certain extent. The areas of the instability zones were observed to gradually increase with increased TiB2 additions. The optimal deformation conditions of the studied materials migrated from a low temperature and high strain rate to a high temperature and low strain rate with increasing TiB2 content. In addition, the flow softening mechanism transformed from dynamic recrystallization + dynamic recovery to dynamic recovery with increasing TiB2 content. Graphic Abstract

    更新日期:2020-01-04
  • Investigation of Microstructure of Aluminum Based Composite Material Obtained by Mechanical Alloying
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-04
    Veysel Erturun, Sezer Çetin, Oguzhan Sahin

    Abstract Aluminum, zinc, magnesium, copper and silicon carbide powders were alloyed by mechanical alloying (MA) at certain ratios and for different periods. At the same time, the zinc effect on the microstructure was investigated by keeping the ratio of zinc in the mixture at different ratios for each mixture. X-ray diffraction (XRD) analysis was carried out to investigate the different phases. Analyzes of the microstructures of alloys with different alloying times were investigated by scanning electron microscopy (SEM) and optical microscope. The powders obtained by the MA method sintered in an argon atmosphere, which is a protective gas, to obtain billets from the powder samples. Finally, the billets were polished and then examined under an optical microscope. Graphic Abstract

    更新日期:2020-01-04
  • Preparation of Ultrafine Tungsten-Molybdenum Composite Powder and Its Sintering Behavior
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-04
    He Zhang, Guo-Hua Zhang

    In this paper, a new method for preparing ultrafine tungsten-molybdenum composite powders has been proposed. The carbothermic pre-reduction of the mixture of molybdenum trioxide and tungsten trioxide with insufficient carbon black under argon atmosphere was carried out, to generate the pre-reduced tungsten-molybdenum composite powder containing a small amount of residual dioxide. Thereafter, the obtained reaction product was subjected to hydrogen reduction to remove the residual dioxide and generate pure tungsten-molybdenum composite powder with the particle size of 100–200 nm. Two kinds of ultrafine tungsten-molybdenum alloy powders (Mo-30 wt% W, Mo-70 wt% W) were prepared. The residual carbon of the finally obtained product was about 0.01–0.02 wt% after the hydrogen reduction. The sintering behavior of ultrafine W–Mo powders and the properties of sintered samples are investigated. After sintering ultrafine Mo-30 wt% W and Mo-70 wt% W powders at 1600 °C, the relative density of the sintered compacts was about 99%, 97%, and the microhardness were 287 HV and 350 HV, respectively. Meanwhile, as increasing the sintering temperature from 1200 to 1600 °C, the relative density and microhardness of the compacts gradually increased.

    更新日期:2020-01-04
  • Nanostructural Evolution and Deformation Mechanisms of Severely Deformed Pure Fe
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-04
    N. Forouzanmehr, H. R. Jafarian, M. Samadi-khoshkhoo, M. Bönisch, M. Nili-Ahmadabadi

    Microstructural evolution and mechanical behavior of commercially pure Fe during severe deformation by cold caliber rolling followed by wire drawing were investigated using transmission electron microscopy and electron backscatter diffraction. Following by a drastic increment of strength in the early stage of deformation, shear banding as a softening mechanism leads to decreasing of work hardening rate and finally a steady state situation at medium strains, creating a bimodal microstructure. Increasing strain beyond 3 is associated with increasing the rate of work hardening and refinement of the material. Severely deformed Fe after cold caliber rolling to equivalent strain of 4.5 evolves from lamellar ultrafine-grained structure. Additional deformation by drawing results in more homogeneous structure and activates new mechanisms. A dynamic recovery appears at severe strains through mechanically assisted triple junction motion. It is found that suppression of triple junction motion enhances the refinement of microstructure and the strength, such that the highly deformed Fe after equivalent strain of 7 has a nano/ultrafine-grained structure combined with a high tensile strength of 1115 MPa.

    更新日期:2020-01-04
  • Effects of Fe 2 O 3 and B 4 C Addition on the Mechanical Properties and Corrosion Resistance of Al–Mg–Si Alloy in 3.5% Brine Solution
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-03
    Mummoorthi Duraipandian

    Abstract In this present investigation aluminum Al6061 alloy and 5 wt% of Fe2O3 in addition to 2%, 4%, 6% weight of B4C reinforced matrix composites (AMCs) is fabricated by stir casting method. Upon increasing the amount of weight percentage to the composites, the mechanical properties also increased. The AC impedance spectra and polarization studies have been utilized to investigate the resistance towards corrosion of the Fe2O3 and B4C reinforced Al6061 metal matrix composites (AMCs). Corrosion current (Icorr), Linear Polarization Resistance (LPR), corrosion potential (Ecorr), capacitance (C), charge transfer resistance (Rct) parameters were considered by the materials submerged in 3.5% of Brine solution and the resistance towards corrosion of the material is determined. Scanning Electron Microscopy (SEM) is utilized to identify the before and after corrosion of the prepared composites. The resistance towards the corrosion is significantly increased with increasing the wt% of reinforced composites. Graphic Abstract

    更新日期:2020-01-04
  • Micro-Cracking in Medium-Carbon Steel Layers Additively Deposited on Gray Cast Iron Using Directed Energy Deposition
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-03
    Seulbi Lee, Jaewoong Kim, Do-Sik Shim, Sang-Hu Park, Yoon Suk Choi

    Abstract Single track and multi-layers of medium-carbon steel (AISI H13) powders were additively deposited on gray cast iron using a directed energy deposition (DED) technique. Multi-scale microstructure characterization using a scanning electron microscopy, an electron probe micro-analyzer and a scanning transmission electron microscopy, and the thermal analysis using finite element method were performed to understand the mechanism for the micro-crack formation, which was found at the single, double and triple layers of medium-carbon steel powders, except for the single track, deposited on a cast iron substrate. The crack formation mechanism was thoroughly investigated by combining the layer-by-layer chemistry variations and the resulting microstructural evolution upon exposure to thermal cycles during the DED process. It was concluded that micro-cracking was accompanied by the initiation of the local graphitization and the formation of plate martensite in the vicinity, which seemed to be kinetically facilitated by an indirect exposure to multiple heating–cooling thermal cycles, not by a direct exposure to a melting-cooling (solidification) cycle. Graphic Abstract

    更新日期:2020-01-04
  • Numerical Simulation of Surface Softening Behavior for Laser Heat Treated Cu-Bearing Medium Carbon Steel
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-03
    Ahjin Sim, Eun-Joon Chun, Dae-Won Cho

    The critical temperature condition for softening behavior of AISI P21 steel during laser-assisted heat treatment is suggested by three-dimensional transient simulation with a finite different method. Temperature history of the cross-sectional region during laser-assisted heat treatment at 1273 K was simulated. The critical temperature condition for formation of the softening zone was assumed to range from 900 to 1008 K, based on this peak temperature history. Formation of the softening zone was simulated based on the assumed critical temperature condition. Morphology and area of simulated softening zone was compared with the experimentally obtained results, and these were well matched. In this regard, critical temperature condition for formation of the softening zone during laser-assisted heat treatment was identified to range from 900 to 1008 K.

    更新日期:2020-01-04
  • Effect of Zinc Content and Cutting Tool Coating on the Machinability of the Al-(5–35) Zn Alloys
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-03
    Şenol Bayraktar, Ali Paşa Hekimoğlu

    Abstract In this study, Al-5Zn, Al-15Zn, Al-25Zn and Al-35Zn alloys containing 5, 15, 25 and 35 wt% Zn, respectively were produced by permanent mold casting. Their microstructures and mechanical properties were investigated using metallography and universal hardness and tensile tests. Cutting tests of the alloys produced were carried out in a vertical machining center. During the tests, the cutting forces were continuously measured and saved by a software. The roughness of the machined surfaces of the alloy samples was measured accordance with the standard of ISO 4287. It was observed that Al-(5–15)Zn alloys exhibit single phase (aluminum rich α) microstructure while Al-(25–35)Zn alloys exhibit two-phase microstructure consisting of α and zinc rich η. As the zinc content increased the hardness and tensile strength of the alloys increased, but their elongation to fracture decreased. Cutting force, surface roughness, formation of built-up edge (BUE) and built-up layer (BUL), and the size of the chip occurring in the machining of the alloys decreased with increasing zinc content. The machining of the Al-(5-35)Zn alloys with uncoated WC tools results in both lower cutting forces and better surface quality compared to titanium-aluminum-nitride (TiAlN) coated tools. The changes in the cutting properties of the tested alloys with the increasing zinc content were discussed in the based on changes in structural and mechanical properties. Graphic Abstract

    更新日期:2020-01-04
  • Preparation and Improved Friction and Wear Performance of the Nano-MoSi 2 Coating on Ni Substrate by Plasma Spraying
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-03
    Mohammad Erfanmanesh, Saeed Reza Bakhshi, Mohammad Reza Pakmanesh, Masoud Barekat

    Abstract In this work, the wear performance of nano- and ordinary MoSi2 plasma-sprayed coating on Ni substrate are compared. MoSi2 nanopowder is prepared by ball milling followed by heat treatment processes. Atmospheric plasma spraying with argon atmosphere protection has been used to deposit the powders onto the nickel substrate. Ni substrate, MoSi2 coating, and nano-MoSi2 coating were subjected to reciprocating wear test. Wear tests were done on a pin on plate machine by sliding MoSi2 coating and substrates without coating against 52100 steel as the pin, at a temperature of 27 °C in dry condition. A friction coefficient of 0.18 ± 0.1 is obtained for nanostructured MoSi2 coating, whereas a friction coefficient of 0.2 ± 0.1 is obtained for conventional MoSi2 coating under normal load of 20 N. Wear performance of nanostructured MoSi2 coating was better as compared to the conventional MoSi2 coating. The three observed dominant types of wear mechanisms were adhesive, oxidation and abrasive. Morphologies and phases of coating, wear tracks, wear debris and counterpart steel pins were evaluated by SEM with EDS and X-ray diffraction. The microhardness and adhesion strength of nanostructured MoSi2 coating are determined by 1000 HV and 27 MPa, respectively. Graphic Abstract

    更新日期:2020-01-04
  • Fabrication and High-Temperature Compressive Behavior of Unique Multi-Sheet Stacked Block Ni–Cr–Al Metallic Foam
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-02
    Kyu-Sik Kim, Tae-Hoon Kang, Man-Ho Park, Kee-Ahn Lee

    Large unique block Ni–Cr–Al superalloy foam was fabricated using a combination method of powder-alloying, multi-sheet stacking, and hot compression processes. Subsequently, the compressive properties and deformation behaviors of multi-sheet stacked block metallic foam were investigated from room temperature to 1073 K. The analysis of the resulting structural characteristics of the block foam showed that the interfaces between the sheets have complex strut interactions, such as contacted (deformed) and intersected struts. The relative density was measured as 2.93% for sheet foam and 4.90% for block foam. The compressive deformation of sheet and block Ni–Cr–Al foams showed the typical compressive stress–strain curves of plastically deformable metallic foams regardless of foam type. However, different deformation behaviors in the plateau regions were detected based on the type of foam. It is noteworthy that the yield strength of block foam showed a relatively lower value than that of sheet foam, even though the block foam had higher relative density. The existence of unique interfaces in the multi-sheet stacked block foam may have affected strength and plastic deformation. Finally, distinct compressive behaviors related to the structural and microstructural characteristics of block Ni–Cr–Al foam are discussed.

    更新日期:2020-01-04
  • Microstructure, Mechanical Properties and Tribological Behavior of Two-Phase Mg–Y–Cu Alloys with Long Period Stacking Ordered Phases
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-02
    L. Zhang, H. Huang, S. J. Zhang, X. R. Liu

    Abstract This study is undertaken to investigate the microstructure, mechanical properties and tribological behavior of as-cast Mg100−3xY2xCux (at%, x = 0.5, 1, 1.5 and 2) alloys. The results show that all the alloys had a two-phase structure consisting of α-Mg matrix and 18R long period stacking ordered phase. With increasing Y and Cu contents, the average grain size of primary α-Mg gradually decreased from 1280 to 146 μm, meanwhile, the volume fraction of long period stacking ordered phase rapidly increased from 11.8 to 56.4%. As Y and Cu contents increased, the tensile strength and hardness of as-cast alloys were gradually enhanced. The yield strength, ultimate tensile strength and hardness of the Mg94Y4Cu2 alloy were 188 MPa, 252 MPa and 86.7 HB respectively, which were increased by 144.2%, 78.7% and 20.2% compared with the Mg98.5Y1Cu0.5 alloy. The friction coefficient and the wear rate of as-cast alloys decreased firstly and then increased as Y and Cu contents increased. The Mg95.5Y3Cu1.5 alloy exhibited the lowest friction coefficient and the best wear resistance. Graphic Abstract

    更新日期:2020-01-02
  • Modeling the Age-Hardening Process of Aluminum Alloys Containing the Prolate/Oblate Shape Precipitates
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-02
    Nozar Anjabin

    Abstract Non-spherical precipitates are the main strengthening source of the age-hardenable aluminum alloys. In the majority of the precipitation hardening models presented so far, the simple spherical shape has been assumed. Moreover, the models which considered the actual shape of the precipitates, are derived based on the simple assumption of steady-state diffusion problem solutions. In the present study, the classical Kampmann and Wagner numerical model of spherical precipitates is extended to model the kinetics of spheroidal shape precipitates evolution during the aging treatment of Al alloys. To do so, a new rate law is proposed using a similarity solution of the transient diffusion problem around the spheroidal precipitates, with different aspect ratios, and moving boundaries. Moreover, a modified age-hardening model which considered the effects of precipitate shape, size and volume fraction, is used to predict the variation of the alloy hardness during the aging process. The accuracy of the proposed model is shown by comparing the predicted features of precipitates, and hardness evolution with the published experimental data. Also, the validity of the existing approximate solutions for the aging problem is discussed. Graphic Abstract

    更新日期:2020-01-02
  • Effect of Microstructure on High Cycle Fatigue and Fatigue Crack Propagation Behaviors of β-Annealed Ti–6Al–4V Alloy
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-01
    Heesoo Choi, Sumin Kim, Yongnam Kwon, Masahiro Goto, Sangshik Kim

    Abstract High cycle fatigue (HCF) and fatigue crack propagation (FCP) behaviors of β-annealed Ti64 alloys having a microstructure of either α colonies or basketweave were studied. It was found that the resistance to HCF of β-annealed Ti64 alloys with a microstructure of α colonies was similar but slightly inferior to those with a microstructure of basketweave. On the other hand, the FCP rates of β-annealed Ti64 alloys having a microstructure of α colonies were lower than those of basketweave, particularly in low ΔK regime. Crack path observation on the surfaces of β-annealed Ti64 alloy specimens suggested that crystallographic crack growth prevailed in the microstructure of α colonies, leaving cleavage facets on the fracture surface and less fatigue damage at the tip of crack. Based on the fractographic and micrographic examination, the effects of microstructure on the HCF and FCP behaviors of β-annealed Ti64 alloys were discussed. Graphic Abstract

    更新日期:2020-01-02
  • Study on Deformation of Closed-Cell Aluminum Foam in Different Solid–Liquid–Gas Coexisting State
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-01
    Zhiyong Liu, Ying Cheng, Yanxiang Li, Ningzhen Wang, Xu Zhou

    The deformation of closed-cell aluminum foam (CAF) in different solid–liquid–gas coexisting state was studied in this paper. The results showed that the most suitable temperature of the CAF deformation was about 635 °C, which made the CAF have maximum deformation, but its characteristic parameters changed slightly. Moreover, the multi-grain cell wall and small size cell were helpful to the CAF deformation in the solid–liquid–gas coexisting state. When the CAF deformed at 635 °C, the inter-granular solidification microstructure and part of the primary α-Al grain were melted into liquid. The fixed or inter-locked primary α-Al grain was released and changed into the distributed discretely near-spherical grain, making the cell wall have good thixotropy. At the same time, the gas pressure in the cell was recovered to the foaming stage, so the gas pressure could be close to the flow stress of cell wall. During the CAF deformation in the solid–liquid–gas coexisting state, the cell wall deformed in thixotropic under the supporting and coordinating of the gas pressure in the cell, meanwhile, the cell was moved following the cell wall deformation. Therefore, the CAF deformation was affected by the types of the cell walls and the cell size.

    更新日期:2020-01-01
  • Material Selection: Exploring the Reliability of Material Perception Data and Its Relevance to Materials
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-24
    Jaeho Choi

    Abstract Identifying and evaluating the diffuse interface between the users’ material perceptions and the designer’s intended product personalities is a key aspect of decision making in user centred design. As such, acquiring reliable information on the material perceptions of users is vital for studying material selection using the diffuse interface. To verify the reliability of material perception data and its relevance to materials, two surveys on material perceptions were conducted using two different groups. The data were analysed by priority fluctuation, the p value of a hypothesis test of the difference in two proportions, and the Pearson coefficient and p value of a correlation analysis. The results revealed that conducting multiple surveys using statistically validated adjective pairs and merging the data can provide more objective material perception data of a large number of participants. Moreover, by creating a large database of statistically validated adjective pairs, designers will have access to a variety of material perception data to enable more appropriate material selection to meet the diverse needs of users. Suitable material can be selected by employing the Euclidean distance between users’ common perceptions of materials and the designer’s intended product personalities. Graphic Abstract

    更新日期:2019-12-25
  • Dislocation Damping and Defect Friction Damping in Magnesium: Molecular Dynamics Study
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-21
    Jingyu Zhai, Xinyuan Song, Anyang Xu, Yugang Chen, Qingkai Han

    Abstract In this study, the molecular dynamics method was used to study the damping mechanism in Mg alloys at the atomic scale. The energy dissipated by the nucleation and motion of dislocations and by defects friction, and the effect of defects, such as vacancies, cracks, and grain boundaries, on them were studied. The study shows that different kinds of defect have different effects on the dislocation damping and defect friction damping. And then, the effect of strain amplitude and temperature on damping capacity of Mg was studied. The result shows that the amplitude independent damping is caused by defect friction and the amplitude dependent damping is mainly caused by the nucleation and motion of dislocation; the damping of Mg increased exponentially with the temperature, and the damping peck appeared at 440 K is attributed to the appearance of dislocations at the grain boundaries which may be caused by boundaries self-diffusion. Graphic Abstract

    更新日期:2019-12-21
  • Effects of Mn Content on Microstructure, Mechanical and Dry Sliding Wear Properties of Eutectic Al–Si–Cu Alloy
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-20
    Yasin Alemdag, Murat Beder

    In the present study, effects of Mn content on microstructure, hardness, tensile and dry sliding wear properties of eutectic Al–Si–Cu alloy in as cast-state were investigated. Mn addition to the eutectic alloy results in the formation of α-Al15Mn3Si2 phase in its microstructure. It was found that hardness of eutectic alloy increases continuously with increasing Mn content while its tensile strength and percentage elongation values decrease. It was also found that the friction coefficient and volume loss of eutectic alloy decrease as Mn content increases. Amongst the alloys, the lowest friction coefficient is obtained with Al–12Si–3Cu–2Mn alloy yet the Al–12Si–3Cu–1Mn alloy exhibits the highest wear resistance. Formation of adhesion layer, its oxidation and delamination were observed to be main wear mechanisms of Al–12Si–3Cu–(0–2)Mn alloys. These findings are explained in terms of formation of α-Al15Mn3Si2 phase, and its cracking tendency effect.

    更新日期:2019-12-21
  • Microstructure and Tensile Strength of Nano-TiC p /Mg–Zn–Ca Magnesium Matrix Nanocomposites Processed by Multidirectional Forging
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-18
    K. B. Nie, Z. H. Zhu, K. K. Deng, Y. C. Guo, J. G. Han

    In this work, a Mg–Zn–Ca magnesium matrix nanocomposite containing nano-sized TiC particles was firstly processed by multidirectional forging (MDF). With increasing the forging temperature from 230 to 310 °C for 1 MDF pass or the number of MDF passes at 270 °C, both volume fractions and average sizes of recrystallized grains increased. The average sizes of precipitated MgZn2 phases increased with the increase in either the initial forging temperature or MDF passes, and the volume fractions gradually decreased with increasing the initial forging temperature or decreasing the MDF passes. With decreasing the initial MDF temperature, thermal expansion mismatch strengthening slightly decreased while fine-grain strengthening and Orowan strengthening gradually increased, resulting in a gradual increased yield strength. The elongation of the present nanocomposite gradually increased from 8.2% after 1 MDF pass to 22.7% after 6 MDF passes, while both yield strength and ultimate tensile strength did not change significantly. This could be ascribed to that although the fine-grain strengthening gradually reduced, there was no significant change in the Orowan strengthening caused by MgZn2 phases with increasing the number of MDF passes.

    更新日期:2019-12-19
  • Microstructure, Mechanical Properties and Wear Performance of WC/Brass Composites Produced by Pressureless and Spark Plasma Sintering Processes
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-16
    Mehdi Naghikhani, Mohammad Ardestani, Mohammad Moazami-Goudarzi

    Tungsten carbide reinforced brass matrix composites with 30 and 70 wt% brass were synthesized by mechanical milling and densification of brass/tungsten carbide powder mixtures. Two different sintering methods included pressureless and spark plasma sintering were applied for densification of the milled powders. The relative density of the spark plasma sintered samples was much higher than those of the pressureless sintered ones confirming higher microstructural densification during spark plasma sintering. The hardness of the spark plasma sintered composites containing 30 and 70 wt% brass were 303 and 175 Vickers, respectively which was about five times more than those of the pressureless sintered composites with similar weight percent of brass. In addition, the wear performance of the composites was investigated by the pin on disc method. The spark plasma sintered samples with 30 wt% brass showed the highest wear resistant among the processed samples owing to their higher hardness. The microscopic observations revealed that delamination and adhesion were the dominant wear mechanisms for the pressureless and spark plasma sintered composites, respectively. The bending strength of the spark plasma sintered samples with 30 and 70 wt% brass were 329 and 453 MPa, respectively.

    更新日期:2019-12-17
  • Nano-CeO 2 Doped Cu–Al–Ni SMAs with Enhanced Mechanical as well as Shape Recovery Characteristics
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-09
    Shahadat Hussain, Abhishek Pandey, Rupa Dasgupta

    Effect of nano-CeO2 doping was studied on self-accommodating Cu–12Al–4Ni based shape memory alloys. Cu–Al–Ni based alloys are known for their high thermal stability and good shape memory properties but mechanical processing of these alloys is very difficult due to their high brittle nature and susceptibility to inter-granular failure. The present work deals with the enhancement of mechanical as well as shape recovery characteristics of these alloys with the addition of nano-CeO2. Significant improvements in ductility (1.8 times), strength and shape recovery were observed with the addition of nano-CeO2 with respect to the base alloy.

    更新日期:2019-12-11
  • Influence of Thermomechanical Treatments on the Microstructure and Mechanical Properties of Aluminium Alloy AA2219 Hand Forgings
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-09
    M. Arumugam, P. Ramesh Narayanan, V. Muthupandi

    The heat treatable aluminium alloy AA2219 is subjected to mechanical stress relieving by way of cold deformation after solution treatment to relieve the quenched in stresses as thermal stress relieving is not possible due to the requirement of higher temperature than the ageing temperature. Cold deformation prior to aging has also been found to yield improved strength. Though this phenomenon is to some extent being exploited in aluminium alloy AA2219 sheets and plates, there is no experimental data available to understand the influence of cold compression on the extent of benefits obtainable on mechanical properties in forgings. In the present study to identify a thermo-mechanical treatment that can yield the maximum tensile strength, solution treated AA2219 forgings were subjected to cold deformation ranging from 0 to 25% and then artificially aged. The results indicates that the maximum room temperature tensile strength (both UTS and 0.2% PS) can be obtained at 10% post solution treatment cold deformation. As this alloy is being used for low temperature applications, it is very essential to assess the effect of higher cold compression on the low temperature (77 K) properties and the results show that the 77 K tensile properties more or less same beyond 2% cold deformation. As the weld properties are around 50% of the parent metal properties, any increase in the mechanical properties, is considered to be very crucial and very much needed for this alloy in the absence of aluminium–lithium alloy technology. Hence this study indicate that there is a good scope to increase the amount of cold compression after Solution treatment instead of restricting the same to 2%–5% maximum.

    更新日期:2019-12-11
  • Extraction, Distribution, and Precipitation Mechanism of TiN–MnS Complex Inclusions in Al-Killed Titanium Alloyed Interstitial Free Steel
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-07
    Shuai Gao, Min Wang, Jian-long Guo, Hao Wang, Jian-guo Zhi, Yan-ping Bao

    The TiN–MnS complex inclusions in Al-killed titanium alloyed interstitial free steel were extracted from the slabs using an electrolytic aqueous solution method. Scanning electron microscopy with energy spectroscopy analysis and an automatic scanning electron microscope were employed to analyze the size and distribution of TiN–MnS inclusions in the thickness direction of the slab. It was found that TiN–MnS complex inclusions were primarily concentrated in the 1/4 thickness direction from the inner and outer surfaces, and the size of the complex inclusions in the slab center was approximately 8 μm. TiN began to precipitate when the solidification rate reached 0.646–0.680 in the δ phase, and MnS would appear in the γ phase when the solidification rate exceeded 0.450 through thermodynamic analysis. Also, the formation mechanism of the complex TiN–MnS was investigated under a crystal structure during solidification.

    更新日期:2019-12-11
  • Phase Stability and Thermo-Physical Properties of Nickel-Aluminum Binary Chemically Disordered Systems via First-Principles Study
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-07
    Zhiqin Wen, Yuhong Zhao, Jianhua Li, Hua Hou

    The effect of Al content and crystal structures on ground state, phase stability, elasticity and thermodynamics of Ni1−xAlx (x = 0.25, 0.50 and 0.75) binary chemically disordered systems are investigated using first-principles method in combination with quasi-harmonic Debye-Grüneisen model. The special quasirandom structures are applied to model disordered body-centered cubic (bcc) and face-centered cubic (fcc) phases. The Gibbs free energy of mixing of equiatomic Ni0.5Al0.5 is the lowest. The nonmagnetic fcc structure’ Ni1−xAlx are predicted to be more favorable phases. Disordered Ni1−xAlx are less stable than ordered L21 Ni3Al and B2 NiAl, and L21 phase is the most likely to form a nuclear growth. The somewhat different impact of Al content on elastic properties has been extracted that the resistance to volume change, shear deformation and elastic deformation of Ni1−xAlx decrease with increasing Al content. For bcc and fcc phases, Ni0.75Al0.25 and Ni0.25Al0.75 are predicted to be ductile behavior, while Ni0.5Al0.5 exhibit brittleness. The structural, vibrational and electronic contributions are taken into account to study the thermodynamic properties at finite temperature. The lattice constants a and volumetric thermal expansion coefficient α of Ni1−xAlx systems increase with the increase of Al content. Nevertheless, it is decreasing for heat capacity Cv and Cvvib. The vibrational entropy Svib of bcc Ni0.25Al0.75 is the largest in considered temperature. The α, Cvvib and Svib of disordered Ni1−xAlx are larger than that of ordered Ni3Al and NiAl. Vibrational and electronic entropy are the dominating at finite temperature stabilization mechanism.

    更新日期:2019-12-11
  • Enhancement of Impurity, Machinability and Mechanical Properties in Te-Treated 0Cr18Ni9 Steel
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-06
    Jian-bo Xie, Tian Fan, Han Sun, Zhi-qi Zeng, Jian-xun Fu

    To enhance the machinability and mechanical properties of 0Cr18Ni9 steel, free-machining element Te was introduced in this work. By adding various quantities of Te to steel, several machining and tensile tests were carried out. Results show that with Te addition of 530 ppm, the number of inclusion sizes below 1 μm disappeared. With raising Te from 360 to 530 ppm, more MnTe–MnS inclusions of 10–40 μm were in spherical shape; above 50 μm2, the ratio of inclusion area at 530 ppm was greatest among all, and the large-sized inclusions occupied a larger share. Te addition contributed to the surfaces of machining steels more smooth. The ultimate tensile strength of steel increased from 399 to 435 MPa. Te resulted in growth of sulfides and improved the machinability of steel.

    更新日期:2019-12-11
  • High Temperature Mechanical Properties and Microstructures of Thermally Stabilized Fe-Based Alloys Synthesized by Mechanical Alloying Followed by Hot Extrusion
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-06
    Hasan Kotan, Kris A. Darling, Tom Luckenbaugh

    The key requirement to consolidate high-energy mechanically alloyed nanocrystalline powders is to achieve densification and particle bonding without impairment in the mechanical properties. Recent demonstrations of consolidation methods involving high shear, pressure and temperature have shown promising results for bonding high strength particulate materials produced by mechanical alloying. In this study, we report the ability of multi-pass high temperature equal channel angular extrusion to produce bulk ferritic alloys from nanocrystalline Fe–Ni–Zr powders. Subsequent microstructural characterizations indicate limited grain growth as the average grain sizes remain smaller than 100 nm after processing temperatures of 600 °C and 700 °C, above which grains reach micron sizes. The compression test results reveal that the alloys exhibit high mechanical strength at room and moderately high temperatures compared to the pure Fe and Fe–Ni alloys without Zr addition.

    更新日期:2019-12-11
  • Manufacturing Methods, Microstructural and Mechanical Properties Evolutions of High-Entropy Alloys: A Review
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-06
    Yaser A. Alshataif, S. Sivasankaran, Fahad A. Al-Mufadi, Abdulaziz S. Alaboodi, Hany R. Ammar

    High entropy alloys (HEAs) are being attracted recently by several researchers, scientists, and academicians to achieve extraordinary and outstanding properties that cannot be obtained from conventional alloys. HEAs are multicomponent alloys in which a minimum of five metallic elements are mixed in an equal molar or non-equal molar ratio. The rapid growth of this field produces a huge amount of scientific papers over the last decade. However, still, there is a need to review various manufacturing methods and their results. Also, the outcome of the scientific articles related to HEAs has ignored the various methods of synthesizing and manufacturing. In this review article, an attempt was made and largely concentrated on the methods and techniques that can be used in the manufacturing and synthesizing of the HEAs. Recently, the properties of HEAs become much better when compared to conventional alloys. Some techniques have succeeded in producing ultrafine microstructure grains which become a leap in industrial fields. Now, the manufacturing methods of conventional alloys are almost familiar and implemented according to the suggestions given by the researchers and academicians based on their work. Therefore, the present review article has demonstrated various methods of manufacturing of HEAs with novel schematics with a preview description for more understanding of the basic work criteria. Besides, this article has reviewed the outcomes of several research articles related to several methods, then compared the outcome of each method with the corresponding mechanical properties, and major challenges of HEAs are discussed and reported.

    更新日期:2019-12-11
  • 27R-SiAlON Reinforced AlN Composite: Synthesis, Sintering and Characterization
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-06
    Mita Biswas, Siddhartha Bandyopadhyay

    Synthesis of powder containing a dual phase mixture of 27R-SiAlON and AlN has been successfully carried out through carbothermal reduction and nitridation route. The probable reaction sequences of formation have been identified through the analysis of transient appearances of intermediate phases associated with parameters like loss of carbon, oxygen and weight as well as nitrogen uptake. Formation of 27R-SiAlON takes place through further reaction of a primary polytype phase, Si3Al7O3N9. FTIR spectra provide supplementary evidence for supporting the revealed model of reaction sequences. Particles are agglomerative in nature consisting of fine grains, as low as below 50 nm in size. Spark plasma sintering was applied for an initial densification trial of this bi-phasic powder without externally added sintering aid. The densified samples exhibited elongated grain-reinforced composite microstructure with improved properties over monolithic AlN.

    更新日期:2019-12-11
  • Effect of Rare Earth Er on Microstructure and Creep Behavior of Al–7Si–0.3Mg Alloy
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-05
    S. Rashno, M. Reihanian, Khalil Ranjbar

    The effect of 0.25 wt% and 0.5 wt% rare earth Er addition on the microstructure and creep behavior of the cast A356 alloy was investigated. The microstructure of the alloys before and after the creep was evaluated by optical and scanning electron microscopy equipped with energy dispersive spectrometry. The creep behavior was examined by the impression creep test at the temperature range of 493 to 553 K under the stresses between 480 and 680 MPa. Results showed that the addition of Er addition caused the α-Al dendrites to refine and the morphology of the eutectic silicon to modify significantly. The microstructure of the A356 alloy with Er addition was characterized by Er-rich intermetallics. The lattice self-diffusion climb-controlled creep was found to be the dominant creep mechanism in all alloys. The addition of Er improved the creep resistance of the A356 alloy and the alloy modified with 0.5 wt% Er exhibited the highest creep resistance.

    更新日期:2019-12-11
  • Effect of SiC Nanofiber Addition on Microstructure, Mechanical Properties and Creep Behaviour of High Pressure Die Cast AZ91-1Sr Alloy
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-05
    Güven Yarkadaş, Hüseyin Şevik

    Effects of nanofiber SiC (0.5 and 1 vol%) addition on microstructure, mechanical properties and creep behaviour of cold chamber high pressure die casting AZ91-1Sr alloy have been investigated. Experimental results indicate that the AZ91-1Sr alloy contains of α-Mg, β-Mg17Al12 and Al4Sr intermetallic phases. With addition of nanofiber SiC, the Al4C3 and SiC peaks were detected. Also, the mechanical properties of the matrix alloy were improved. The AZ91-1Sr-1%SiC nanocomposite displays the best yield strength and hardness increment. Furthermore, the creep resistance of the matrix alloy was increased with increasing nanofiber SiC and the best creep resistance was obtained in the AZ91-1Sr-1SiC nanocomposite. The values of stress exponents and the activation energies for experimental specimen were found between 3.17–5.54 and 103.5–155.3 kJ/mol., respectively. When considered the results obtained from the values of stress exponents, the activation energies and SEM micrographs, it was thought that the dominant creep mechanism for the matrix alloy and nanocomposites is dislocation climb controlled.

    更新日期:2019-12-11
  • In-Situ Synthesis of Aluminum Matrix Composite from Al–NiO System by Mechanical Alloying
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-05
    Samaneh Mamnooni, Ehsan Borhani, Davoud Bovand

    In this paper, Al-based composites reinforced by Alumina and Al–Ni intermetallic compounds have been successfully fabricated by mechanical alloying technique. The intermetallic phase, i.e., NiAl, NiAl3, Ni2Al3, as well as Alumina, were formed in the aluminum matrix by in situ solid-state reactions between pure Al and NiO powders. The effects of NiO content (7–10–13 vol%) on the characteristics of the fabricated composites were examined, the hardness, wear properties, phase constituent, and composite microstructure with different NiO content in particular. The results showed that the addition of NiO to Al increases the formation of Al–Ni system intermetallic compounds and enhance the surface hardness. Further, it is ascertained that Al–10 vol% NiO nanocomposite has better wear properties in comparison with samples with 7 and 13 vol% NiO due to the better matrix integrity and reinforcement distribution in the Al matrix.

    更新日期:2019-12-11
  • Hydrogen Behavior in Ti-Added Reduced Activation Ferritic-Martensitic Steels
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-05
    Kang-Mook Ryu, Dae Geon Lee, Joonoh Moon, Chang-Hoon Lee, Tae-Ho Lee, Jae Sang Lee, Dong-Woo Suh

    Hydrogen behavior and corresponding mechanical degradation were examined in TaTi-RAFM and EUROFER97 steels. Increased Ta content with Ti addition decelerates the hydrogen diffusion but increases the solubility in the lattice. It is mainly led by the higher fraction of Ta-rich MC carbides and dislocation density in TaTi-RAFM steel. Overall activation energy of hydrogen trapping of investigated steels is evaluated to be 25.3 ~ 25.6 kJ/mol in the tempered condition. The activation energy increases to nearly 30 kJ/mol when the steels are re-austenitized and quenched. Higher activation energy with increased dislocation density indicates that the dislocation provides for trap site with higher activation energy than Ta-rich MC carbide. Mechanical degradation by hydrogen with respect to the yield strength, tensile strength and uniform elongation could not be observed in all investigated steels. The presence of hydrogen only has influence on the loss of post-uniform elongation. For a given charging time, the loss of post-uniform elongation is more remarkable in TaTi-RAFM steel due to the larger hydrogen uptake.

    更新日期:2019-12-11
  • Electropulsing Treatment on Enhancement of Electrical Conductivity of Screen-Printed Ag Wire
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-04
    Ju-Won Park, Howook Choi, Hwangsun Kim, Simoon Sung, Hye-Jin Jeong, Il Kim, Jaeseok Gong, Sung-Tae Hong, Heung Nam Han

    The effect of high electric current density on the sintering of Ag wires manufactured by screen printing is evaluated through electrical resistivity analysis and microstructure observation. Different forms (continuous and pulsed) of electric current with different current densities are applied to the specimens. Conventional heat treatment is also performed as a control group to examine the athermal effect of electropulsing treatment. Compared to the conventional heat treatment, the resistivity is reduced more under the electropulsing treatment with continuous current for the same temperature and treatment time. Also, the process time of electropulsing treatment can be reduced by applying a pulse form of high density current instead of continuous current without losing the benefit of enhanced reduction of resistivity. The microstructural observations obtained from high angle annular dark field scanning transmission electron microscope and a digital precession instrument clearly show that necking connecting the crystals is formed more firmly under electric current. In addition, the temperature change of Ag wire and substrate is calculated according to the change of the resistivity when the electric current is applied to confirm the reliability.

    更新日期:2019-12-11
  • Dynamic Compression Behavior of a Mg–Gd-Based Alloy at Elevated Temperature
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-04
    Changping Tang, Kai Wu, Wenhui Liu, Di Feng, Guoliang Zuo, Wuying Liang, Yue Yang, Xu Chen, Quan Li, Xiao Liu

    The dynamic compression behavior and microstructure evolution at 400 °C of an extruded Mg–8Gd–4Y–Nd–Zr alloy with different tempers were investigated. The peak-aged samples exhibit the highest compressive strength, followed by as-extruded samples and over-aged samples. The highest dynamic compressive strength of 582 MPa was achieved by peak-aged sample compressed at 1224 s−1. The high strength was attributed to the formation of abundant thermally stable βʹ precipitates and some dynamic precipitates. The dynamic compressive strength of peak-aged sample and over-aged sample is not sensitive to strain rates, while that of the as-extruded sample is sensitive to strain rates. The dynamic compressive strength of the as-extruded alloy can reach 535 MPa when compressed at 2024 s−1. The high strength was mainly ascribed to the formation of numerous dynamic precipitates and the work hardening effect caused by dislocations. The cracks are composed of crack that is 45° to loading direction on the cylindrical surface and crack on the compressed surface. Microstructure observation indicates that the crack was easily propagated along the interface between the adiabatic shear band and matrix, grain boundaries. The equilibrium phase β in over-aged sample was unable to hinder the crack propagation.

    更新日期:2019-12-11
  • Electrochemical Polishing of Additively Manufactured Ti–6Al–4V Alloy
    Met. Mater. Int. (IF 1.647) Pub Date : 2019-12-04
    Yifei Zhang, Jianzhong Li, Shuanghang Che, Yanwen Tian

    In this present paper, the electropolishing behavior of Ti–6Al–4V alloy fabricated by additive manufacturing in chloride-containing ethylene glycol electrolyte was surveyed. The impacts of chloride ion on surface quality and oxide film of Ti–6Al–4V were analyzed in dependence on the surface topography, roughness, weight loss ratio and compositions. The visual and microscopic results revealed that the optimally electropolished surface was attained in a 0.4 mol L−1 chloride electrolyte with a decreased surface roughness of 75.04% and a weight loss rate of 4.93%. For lower (CCl−1 ≤ 0.3 mol L−1) or higher concentrations (CCl−1 ≥ 0.5 mol L−1), a smooth and flat surface was not observed due to insufficient reactions or excessive anodic dissolution. During the electropolishing, the titanium oxides nucleated and corresponding surface tension increased, resulting in the formation of a stable TiO2 film on the surface of the Ti–6Al–4V alloy, increasing the corrosion resistance of the specimen.

    更新日期:2019-12-11
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