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ISSN 1005-0302
CN 21-1315/TG
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The journal has been awarded the excellent periodical in China, and its articles are covered by SCI, EI, CA, SA, JST, RJ, CSA, MA, EMA, AIA etc., PASCAL web. ISI web of Science,SCOPUS.

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      20 December 2016, Volume 32 Issue 12 Previous Issue    Next Issue
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    Orginal Article
    A Review on Casting Magnesium Alloys: Modification of Commercial Alloys and Development of New Alloys
    Pan Fusheng,Yang Mingbo,Chen Xianhua
    J. Mater. Sci. Technol., 2016, 32 (12): 1211-1221.  DOI: 10.1016/j.jmst.2016.07.001
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    The research and development status of casting magnesium alloys including the commercial casting alloys and the new types casting alloys are reviewed, with more attention to microstructure and mechanical properties of modified-AZ91, AM60 and WE43 alloys with various additions, and new types of low cost casting alloys and high strength casting alloys. The modification and/or refinement of Mg2Si phase in Mg-Al-Si based casting alloys by various additions are discussed and new purifying technologies for casting magnesium alloys are introduced to improve the performance. The modified AZ81 alloy with reduced impurities is found to have the tensile strength of 280 ± 6 MPa and elongation of 16% ± 0.7%. The fatigue strength of AZ91D alloy could be obviously improved by addition of Ce and Nd. The Mg-16Gd-2Ag-0.3Zr alloy exhibits very high tensile and yield strengths (UTS: 423 MPa and YS: 328 MPa); however, its elongation still needs to be improved.

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    First-principles Calculations of Strengthening Compounds in Magnesium Alloy: A General Review
    Liu Yong,Ren Hui,Hu Wen-Cheng,Li De-Jiang,Zeng Xiao-Qin,Wang Ke-Gang,Lu Jian
    J. Mater. Sci. Technol., 2016, 32 (12): 1222-1231.  DOI: 10.1016/j.jmst.2016.04.003
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    First-principles computation methods play an important role in developing and designing new magnesium alloys. In this article, we present an overview of the first-principles modeling techniques used in recent years to simulate ideal models of the structure of strengthening compounds in Mg alloys. For typical Mg compounds, structural stability, mechanical properties, electronic structure and thermodynamic properties have been discussed. Specifically, the elastic anisotropies of these compounds are examined, which is highly correlated with the possibility of inducing micro-cracks. Furthermore, some heterogeneous nucleation interfaces investigated by first-principles method are reviewed. Some of the theoretical results are compared with available experimental observations. We hope to illustrate that the first-principles computation can help to accelerate the design of new Mg-based materials and the development of materials genome initiative. Remaining problems and future directions in this research field are considered.

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    Suppressing Effect of Heat Treatment on the Portevin-Le Chatelier Phenomenon of Mg-4%Li-6%Zn-1.2%Y Alloy
    Li C.Q.,Xu D.K.,Wang B.J.,Sheng L.Y.,Han E.H.
    J. Mater. Sci. Technol., 2016, 32 (12): 1232-1238.  DOI: 10.1016/j.jmst.2016.09.018
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    Microstructural evolution and Portevin-Le Chatelier (PLC) phenomenon of the as-extruded Mg-4%Li-6%Zn-1.2%Y alloy before and after heat treatment have been investigated. It has been demonstrated that for the as-extruded and solid solution treated (T4) samples, the PLC phenomenon could be obviously observed on tensile stress-strain curves. Moreover, the PLC phenomenon in T4 samples was more salient than that in the as-extruded condition, suggesting that the occurrence of PLC phenomenon was closely related to the super-saturation degree of solute atoms in the matrix. Since most of solute atoms were consumed for the formation of MgZn precipitates (β1′ and a little of β2′) during the subsequent ageing treatment (T6), the PLC phenomenon of T6 samples was eliminated. Meanwhile, due to the pinning effect of the formed MgZn precipitates on mobile dislocations, the tensile strength of T6 samples was relatively higher than those of the other two conditions.

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    Effect of Twin Boundary-Dislocation-Solute Interaction on Detwinning in a Mg-3Al-1Zn Alloy
    Xu Jing,Guan Bo,Yu Huihui,Cao Xuezhen,Xin Yunchang,Liu Qing
    J. Mater. Sci. Technol., 2016, 32 (12): 1239-1244.  DOI: 10.1016/j.jmst.2016.08.023
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    In the present study, the influence of solute atoms together with dislocations at {10\overline{1}2} twin boundary (TB) on mechanical behavior of a detwinning predominant deformation in a Mg alloy AZ31 plate was systematically studied. The results show that a large number of {10\overline{1}2} twins disappear during recompression along the normal direction. Both the TB-dislocation interaction and TB-solute-dislocation interaction can greatly enhance the yield stress of the recompression along the normal direction (ND). However, the solute segregation at {10\overline{1}2} TBs with an intensive interaction with dislocations cannot further enhance the yield stress of ND recompression. The samples with TB-dislocation interaction show a similar working hardening performance with that subjected to a TB-solute-dislocation interaction. Both the TB-dislocation interaction and TB-solute-dislocation interaction greatly reduce the value of work hardening peaks during a detwinning predominant deformation.

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    Effect of Surface Mechanical Attrition Treatment on Tribological Behavior of the AZ31 Alloy
    Xia Shuangwu,Liu Yong,Fu Dongming,Jin Bin,Lu Jian
    J. Mater. Sci. Technol., 2016, 32 (12): 1245-1252.  DOI: 10.1016/j.jmst.2016.05.018
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    By surface mechanical attrition treatment (SMAT), a gradient nano structure (GNS) from the surface to center was generated in the AZ31 alloy sheet. The tribological behavior of AZ31 alloy with GNS was systematically investigated by using dry sliding tests, a 3D surface profile-meter and a scanning electron microscope equipped with an energy-dispersive spectrometer. The experimental results indicate that the Mg alloy with GNS exhibits better wear resistance comparing to the as-received sample, which is associated to the alteration of wear mechanism at different sliding speeds. The Mg alloy with GNS presents the wear mechanism of the abrasive wear at 0.05 m/s and the oxidative wear at 0.5 m/s, respectively. Moreover, the GNS can effectively promote the reaction between the oxygen and worn surface, which leads to a compact oxidation layer at 0.5 m/s. The effect of oxidation layer on the wear resistance of the Mg alloy was also discussed.

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    Evolution of Microstructure, Mechanical Properties and Corrosion Resistance of Ultrasonic Assisted Welded-Brazed Mg/Ti Joint
    Xu Chuan,Sheng Guangmin,Cao Xuezhen,Yuan Xinjian
    J. Mater. Sci. Technol., 2016, 32 (12): 1253-1259.  DOI: 10.1016/j.jmst.2016.08.029
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    Ultrasonic vibration with different powers from 0 kW to 1.6 kW was applied during the tungsten inert gas welding-brazing of Mg/Ti. The microstructures, mechanical properties and corrosion resistance of the ultrasonic assisted tungsten inert gas (U-TIG) welded-brazed Mg/Ti joint were characterized. The results showed that, without being subjected to ultrasonic vibration, coarse columnar α-Mg grains occurred in the fusion zone of Mg/Ti joint. However, with ultrasonic power of 1.2 kW, the average grain size of columnar α-Mg grains was refined from 200 μm to about 50 μm and the tensile strength of joints increased ~18% up to 228 MPa. Besides, high fraction of grain boundaries was introduced by grain refinement, contributing to improve the corrosion resistance in two ways: (i) accelerating the formation of Mg(OH)2 protective layer and (ii) reducing the mismatch and disorder between Mg(OH)2 protective layer and Mg alloy surface.

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    Drag Effects of Solute and Second Phase Distributions on the Grain Growth Kinetics of Pre-Extruded Mg-6Zn Alloy
    Jin Zhaoyang,Yu Donghua,Wu Xintong,Yin Kai,Yan Kai
    J. Mater. Sci. Technol., 2016, 32 (12): 1260-1266.  DOI: 10.1016/j.jmst.2016.06.025
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    In order to control the grain size during hot forming, grain growth behavior of a pre-extruded Mg-6Zn magnesium alloy and its correlation with solute and second phase distribution were investigated. Isothermal annealing was conducted on a Gleeble-1500 thermo-mechanical simulator. The mean grain size Dg of each annealed specimen was measured by the quantitative metallography technique. The grain growth kinetics of the Mg-6Zn alloy annealed at 473-623 K was obtained as Dg4-Dg04=2.25×1011exp(-95450/RT)t by the least square linear regression method. The deviation of grain growth exponent n = 4 from the theoretical value of 2 may be attributed to the presence of solute zinc and second phases which will retard the boundary migration. Microscopic observations show that the non-uniform distribution of grain size for samples pre-extruded or annealed at low temperatures is closely related to the non-uniform distribution of fine and dispersed second phases but not to the non-uniform distribution of solute zinc. This indicates that second phase pinning effect plays an important role in microstructure refinement.

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    Formation Behavior of 14H Long Period Stacking Ordered Structure in Mg-Y-Zn Cast Alloys with Different α-Mg Fractions
    Liu Huan,Xue Feng,Bai Jing,Ma Aibin,Jiang Jinghua
    J. Mater. Sci. Technol., 2016, 32 (12): 1267-1273.  DOI: 10.1016/j.jmst.2016.01.005
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    Phase compositions and microstructure evolutions of three Mg-Y-Zn cast alloys during isothermal annealing at 773 K have been systematically investigated to clarify the formation behavior of 14H long period stacking ordered (LPSO) structure from α-Mg grains. The annealed microstructure characteristics indicate that the 18R phase is thermal stable in Mg86Y8Zn6 alloy where 18R serves as matrix, and 14H lamellar phase only forms within tiny α-Mg slices (less than 1% for volume fraction). The α-Mg grains in Mg88Y8Zn4 and Mg89Y8Zn3 alloys exhibit cellular shape, and 14H phase forms and develops into lamellar shape in these cellular grains after annealing. The results suggest that the presence of α-Mg grains is a requirement for the generation of 14H phase. The nucleation and growth rates of 14H lamellas are accelerated in α-Mg grains with higher concentrations of stacking faults and solute atoms. Moreover, the 14H lamellas are parallel to adjacent 18R plates in Mg86Y8Zn6 alloy, but the 14H phase precipitated in cellular α-Mg grains of Mg88Y8Zn4 and Mg89Y8Zn3 alloys exhibits random orientation relationship with surrounding 18R phase, indicating that the orientation relationship between 14H and 18R phases depends on the relationship between α-Mg grains and 18R phase.

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    Effect of Multi-Pass Equal Channel Angular Pressing on the Microstructure and Mechanical Properties of a Heterogeneous Mg88Y8Zn4 Alloy
    Liu Huan,Cheng Zhaojun,Yan Kai,Yan Jingli,Bai Jing,Jiang Jinghua,Ma Aibin
    J. Mater. Sci. Technol., 2016, 32 (12): 1274-1281.  DOI: 10.1016/j.jmst.2016.05.015
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    The microstructure evolutions and mechanical properties of a heterogeneous Mg88Y8Zn4 (in at.%) alloy during multi-pass equal channel angular pressing (ECAP) were systematically investigated in this work. The results show that four phases, i.e. α-Mg, 18R long period stacking ordered (LPSO) phase, Mg24Y5 and Y-rich phase, are present in cast alloy. During ECAP, dynamic recrystallization (DRX) occurs and the diameter of DRXed α-Mg grains decreases to 0.8 μm. Moreover, precipitation of lamellar 14H LPSO structure is developed within α-Mg phase. Both the refinement of α-Mg grains and precipitation of 14H LPSO contribute to the increase in micro-hardness from 98 HV to 135 HV for α-Mg. In addition, a simplified model describing the evolution of 18R LPSO phase is established, which illustrates that 18R undergoes a four-step morphological evolution with increasing strains during ECAP, i.e. original lath → bent lath → cracked lath → smaller particles. Compression test results indicate that the alloy has been markedly strengthened after multi-pass ECAP, and the main reason for the significantly enhanced mechanical properties could be ascribed to the DRXed α-Mg grains, newly precipitated 14H lamellas, 18R kinking and refined 18R particles.

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    Mechanical Behavior and Microstructure Evolution of a Rolled Magnesium Alloy AZ31B Under Low Stress Triaxiality
    Pan Hongchen,Wang Fenghua,Jin Li,Feng Miaolin,Dong Jie
    J. Mater. Sci. Technol., 2016, 32 (12): 1282-1288.  DOI: 10.1016/j.jmst.2016.10.006
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    Plastic deformation up to final rupture failure of a rolled magnesium (Mg) alloy Mg-3.0Al-1.0Zn-0.34Mn (AZ31B) under low stress triaxiality was investigated. Local strain evolution was quantified by the digital image correlation (DIC) technique analysis with tensile, combined tensile-shear, and shear specimens, corresponding to the stress triaxiality of 1/3, 1/6 and 0, respectively. Stress-strain curves show that the yield stress reduces with the decrease in the stress triaxiality, and obviously exhibits different strain hardening response. Electron backscatter diffraction (EBSD) observations reveal that the twinning behavior depends on stress triaxiality. Before fracture, double twinning is the dominant mechanism at the stress triaxiality of 1/3, while extension twinning is prevalent at the stress triaxiality of 0. Moreover, scanning electron microscopy (SEM) shows that the fracture mechanism is transformed from micro-void growth and coalescence to internal void shearing as the stress triaxiality decreases from 1/3 to 0.

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    Constitutive Modeling and Hot Deformation Behavior of Duplex Structured Mg-Li-Al-Sr Alloy
    Yang Yan,Peng Xiaodong,Ren Fengjuan,Wen Haiming,Su Junfei,Xie Weidong
    J. Mater. Sci. Technol., 2016, 32 (12): 1289-1296.  DOI: 10.1016/j.jmst.2016.11.015
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    Hot deformation behavior of an as-extruded duplex structured Mg-9Li-3Al-2.5Sr alloy is investigated via hot compression tests conducted at 200-350 °C with strain rate of 0.001-1 s-1. The flow behavior of Mg-9Li-3Al-2.5Sr alloy can be described accurately by hyperbolic sine constitutive equation and the average activation energy for deformation is calculated as 143.5 kJ/mol. Based on a dynamic materials model, the processing maps of Mg-9Li-3Al-2.5Sr alloy which describe the variation of power dissipation efficiency are constructed as a function of temperature and strain rate. The processing maps exhibit an area of discontinuous dynamic recrystallization occurring at 280-300 °C with strain rate of 0.001-0.01 s-1, which corresponds to the optimum hot working conditions.

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    Effect of Sr on Grain Refinement of Mg-3%Al Alloy Containing Trace Fe by Carbon-Inoculation
    Du Jun,Shi Yutong,Zhou Mingchuan,Li Wenfang
    J. Mater. Sci. Technol., 2016, 32 (12): 1297-1302.  DOI: 10.1016/j.jmst.2016.05.019
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    Magnesium (Mg)-3% aluminum (Al) (in weight) alloy was modified by carbon (C) inoculation combining with strontium (Sr). The effects of trace 0.1% iron (Fe) addition and operating sequence of carbon-inoculation and Fe addition on the grain size of Mg-3%Al alloy were studied. The results reveal that the Sr addition could effectively suppress grain-coarsening resulted from the inclusion of Fe in the carbon-inoculated Mg-Al alloy. Sr addition could contribute to the formation of the duplex-phase particles that Al-C-rich phases coated on Al-Fe or Al-C-Fe-rich phases, regardless of the Fe addition sequence. These duplex-phase particles should be the potent substrates for α-Mg grains. Consequently, Sr addition could effectively subsidize the inhibiting effect of Fe on grain refinement and the active nuclei were maintained. In other words, Sr plays a counter role in the poisoning effect of Fe on the microstructure of Mg-3%Al alloy.

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    A Novel Melt Processing for Mg Matrix Composites Reinforced by Multiwalled Carbon Nanotubes
    Shi H.L.,Wang X.J.,Zhang C.L.,Li C.D.,Ding C.,Wu K.,Hu X.S.
    J. Mater. Sci. Technol., 2016, 32 (12): 1303-1308.  DOI: 10.1016/j.jmst.2016.05.014
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    ChinaCarbon nanotubes (CNTs) reinforced Mg matrix composites were fabricated by a novel melt processing. The novel processing consisted of two courses: CNTs pre-dispersion and ultrasonic melt processing. Mechanical ball-milling was employed to pre-disperse CNTs on Zinc (Zn) flakes. Serious CNT entanglements were well dispersed to single CNT or tiny clusters on Zn flakes. The ultrasonic melt processing further dispersed CNTs in the Mg melt, especially tiny CNT clusters. Thus, a uniform dispersion of CNTs was achieved in the as-cast composites. Hot extrusion further improved the distribution of CNTs. CNTs increased both the strength and elongation of the matrix alloy. Notably, the elongation of the matrix alloy was enhanced by 40%. Grain refinement and the pulling-out of CNTs resulted in the evident improvement of ductility for the composites.

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    Effects of Grain Refinement by ECAP on the Deformation Resistance of Al Interpreted in Terms of Boundary-Mediated Processes
    Blum W.,Dvo?ák J.,Král P.,Eisenlohr P.,Skleni?ka V.
    J. Mater. Sci. Technol., 2016, 32 (12): 1309-1320.  DOI: 10.1016/j.jmst.2016.08.028
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    Results of a large set of tensile and compressive creep tests on pure Al were reanalyzed for the influence of low- and high-angle grain boundaries on the deformation resistance at the temperature T = 473 K = 0.51Tm where Tm is the melting point. Thermomechanical treatment by equal channel angular pressing followed by heating to T led to strong increase of areal fraction of high-angle boundaries in a structure of subgrains of ≈10-6 m in size, accompanied by significant reduction of subgrain strengthening and of the stress sensitivity of the deformation rate. (Sub)grain strengthening by low-angle boundaries is most effective; the strengthening effect virtually disappears during creep as the boundary spacings coarsen toward their stress-dependent, quasi-stationary size wqs. The same type of coarsening is found for (sub)grain structures with large fraction of high-angle boundaries; in the quasi-stationary state they lead to softening at low and strengthening at high stresses, and a significant increase in tensile fracture strain to values up to 0.8. The results are analogous to former results for Cu and are explained in the same way by the influence of boundaries on storage and recovery of crystal defects and the homogenization of glide.

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    Imaging of Structure Evolution in Solidifying Al-Bi Immiscible Alloys by Synchrotron Radiography
    Lu Wenquan,Zhang Shuguang,Zhang Wei,Li Jianguo
    J. Mater. Sci. Technol., 2016, 32 (12): 1321-1325.  DOI: 10.1016/j.jmst.2016.09.020
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    Using synchrotron X-ray imaging technique, the segregation evolution in solidifying Al-10 wt% Bi immiscible alloys was investigated at different cooling rates. Irrespective of the cooling rate, most of the Bi solute appeared at the upper part of the sample after solidification. The reason for this Bi enrichment phenomenon is different for different cooling rates. Besides Marangoni motion, positive segregation, which has rarely been noticed before, can also make Bi solute transfer to the hot top zone. It is also found that, bubbles (or pores) appear in solidifying Al-10 wt% Bi alloys, and the number of bubbles (or pores) increases with the increase of the cooling rate, while the size of the bubbles (or pores) decreases.

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    Structural Modification of Al65Cu16.5Ti18.5 Amorphous Powder through Annealing and Post Milling: Improving Thermal Stability
    Tan Zhen,Wang Lu,Xue Yunfei,Cheng Xingwang,Zhang Long
    J. Mater. Sci. Technol., 2016, 32 (12): 1326-1331.  DOI: 10.1016/j.jmst.2016.03.007
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    To improve thermal stability of the Al65Cu16.5Ti18.5 amorphous powder, structural modification of the amorphous powder was performed through annealing and post milling. Annealing above the crystallization temperature (Tx) not only induced nanoscale intermetallics to precipitate in the amorphous powder, but also increased Cu atomic percentage within the residual amorphous phase. Post milling induced the amorphization of the nanocrystal intermetallics and the formation of Cu9Al4 from the residual amorphous phase. Thus, a mixed structure consisting of amorphous phase and Cu9Al4 was obtained in the powder after annealing and post milling (the APMed powder). The phase constituent in the APMed powder did not change during the post annealing, which exhibited significantly improved thermal stability in comparison with the as-milled amorphous powder.

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    Effect of Preparation Technique on Microstructure and Hydrogen Storage Properties of LaNi3.8Al1.0Mn0.2 Alloys
    Han X.B.,Qian Y.,Liu W.,Chen D.M.,Yang K.
    J. Mater. Sci. Technol., 2016, 32 (12): 1332-1338.  DOI: 10.1016/j.jmst.2016.11.005
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    LaNi3.8Al1.0Mn0.2 alloy was prepared by vacuum induction melting and melt-spinning. The effects of different preparation techniques of the as-cast, cast then annealed, as-spun and spun then annealed alloys on the microstructure and hydrogen storage properties were investigated. The results indicated that the non-CaCu5 phases in the alloy became tinier and more dispersive after annealing or melt-spinning compared to those of the as-cast one. But in the spun then annealed alloy, the non-CaCu5 phases disappeared and only a single-phase with CaCu5 type structure was found. For all the alloys, the cell volume was increased in an order of as-cast < spun then annealed < cast then annealed < as-spun, and the change of plateau pressure showed the opposite trend with that of the cell volume. The plateau could be flattened after melt-spinning or annealing, and the spun then annealed alloy showed the minimum plateau slope. The absorption kinetics of the alloy was promoted after melt-spinning or annealing. It is suggested that the change in cell volume and compositional homogeneity resulting from different preparation techniques contribute to the difference of the hydrogen storage properties of the investigated alloys.

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    Synthesis of α-Mo2C by Carburization of α-MoO3 Nanowires and Its Electrocatalytic Activity towards Tri-iodide Reduction for Dye-Sensitized Solar Cells
    Theerthagiri J.,Senthil R.A.,Buraidah M.H.,Madhavan J.,Arof A.K.
    J. Mater. Sci. Technol., 2016, 32 (12): 1339-1344.  DOI: 10.1016/j.jmst.2016.03.003
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    Nanowire-shaped α-MoO3 was synthesized on a large scale by hydrothermal route. Nanocrystalline α-Mo2C phase was obtained by the carburization of α-MoO3 nanowires with urea as a carbon source precursor. The phase purity and crystalline size of the synthesized materials were ascertained by using powder X-ray diffraction. The shape and morphology of synthesized materials were characterized by field-emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HR-TEM). The electrocatalytic activity of α-Mo2C for I-/I3- redox couple was investigated by the cyclic voltammetry. The synthesized α-Mo2C was subsequently applied as counter electrode in dye-sensitized solar cells to replace the expensive platinum.

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    Probabilistic Analysis and Design of HCP Nanowires: An Efficient Surrogate Based Molecular Dynamics Simulation Approach
    Mukhopadhyay T.,Mahata A.,Dey S.,Adhikari S.
    J. Mater. Sci. Technol., 2016, 32 (12): 1345-1351.  DOI: 10.1016/j.jmst.2016.07.019
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    We investigate the dependency of strain rate, temperature and size on yield strength of hexagonal close packed (HCP) nanowires based on large-scale molecular dynamics (MD) simulation. A variance-based analysis has been proposed to quantify relative sensitivity of the three controlling factors on the yield strength of the material. One of the major drawbacks of conventional MD simulation based studies is that the simulations are computationally very intensive and economically expensive. Large scale molecular dynamics simulation needs supercomputing access and the larger the number of atoms, the longer it takes time and computational resources. For this reason it becomes practically impossible to perform a robust and comprehensive analysis that requires multiple simulations such as sensitivity analysis, uncertainty quantification and optimization. We propose a novel surrogate based molecular dynamics (SBMD) simulation approach that enables us to carry out thousands of virtual simulations for different combinations of the controlling factors in a computationally efficient way by performing only few MD simulations. Following the SBMD simulation approach an efficient optimum design scheme has been developed to predict optimized size of the nanowire to maximize the yield strength. Subsequently the effect of inevitable uncertainty associated with the controlling factors has been quantified using Monte Carlo simulation. Though we have confined our analyses in this article for Magnesium nanowires only, the proposed approach can be extended to other materials for computationally intensive nano-scale investigation involving multiple factors of influence.

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    Mechanical Properties and Interfacial Interaction of Modified Calcium Sulfate Whisker/Poly(Vinyl Chloride) Composites
    Yuan Wenjin,Cui Jiayang,Xu Shiai
    J. Mater. Sci. Technol., 2016, 32 (12): 1352-1360.  DOI: 10.1016/j.jmst.2016.05.016
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    Calcium sulfate whiskers (CSWs) modified with glutaraldehyde-crosslinked poly(vinyl alcohol) (PVA) or traditional surface modifiers, including silane coupling agent, titanate coupling agent and stearic acid, were used to strengthen poly(vinyl chloride) (PVC), and the morphologies, mechanical and heat resistant properties of the resulting composites were compared. The results clearly show that glutaraldehyde cross-linked PVA modified CSW/PVC composite (cPVA@CSW/PVC) has the strongest interfacial interaction, good and stable mechanical and heat resistant properties. Nielsen's modified Kerner's equation for Young's modulus is better than other models examined for the CSW/PVC composites. The half debonding angle θ of cPVA@CSW/PVC composite is lower than that of other composites except silane coupling agent modified CSW/PVC composites, indicating a very strong interfacial adhesion between cPVA@CSW and PVC. In general, cross-linked PVA is effective and environmentally friendly in modifying inorganic fillers.

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    Core-Shell Structure and Luminescence of SrMoO4:Eu3+ (10%) Phosphors
    Zhu Yanan,Zheng Ganhong,Dai Zhenxiang,Zhang Lingyun,Mu Jingjing
    J. Mater. Sci. Technol., 2016, 32 (12): 1361-1371.  DOI: 10.1016/j.jmst.2016.04.018
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    SrMoO4:Eu3+ (10%) phosphors were produced via hydrothermal synthesis and co-precipitation. We systematically analyzed how the morphology and luminescence properties of the phosphors were affected by the synthesis conditions, including the pH of the precursor solution, stirring speed, and post-sintering temperature. The samples synthesized at pH = 8 and 9 were spindle-like rods with a core-shell structure. When the stirring speed increased to Vs = 150 r/min, the core-shell structure disappeared. Photoluminescence measurements indicated that the SrMoO4:Eu3+ samples under ultraviolet radiation produced strong red emission centered at 616 nm. The luminescence properties were greatly affected by the pH, stirring during hydrothermal reaction, and use of post-annealing. The related mechansim is discussed.

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    Improving Joint Features and Mechanical Properties of Pinless Fiction Stir Welding of Alcald 2A12-T4 Aluminum Alloy
    Liu Zhenlei,Cui Hutao,Ji Shude,Xu Minqiang,Meng Xiangchen
    J. Mater. Sci. Technol., 2016, 32 (12): 1372-1377.  DOI: 10.1016/j.jmst.2016.07.003
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    As a new solid state welding, pinless friction stir welding (PFSW) can be used to join thin-wall structures. In this study, four new pinless tools with different groove distributions were designed and manufactured in order to enrich technological storage of PFSW and obtain sound joint with high quality of alclad 2A12-T4 alloy. The results show that the small-obliquity tool is detrimental to the transfer of plasticized materials, resulting in the formation of kissing bond defect. For the through-groove tool or the large-curvature tool, bigger flashes form on the joint surface and alclad layer is observed in the nugget zone (NZ), deteriorating mechanical properties. Compared with the above-mentioned three tools, using the six-groove tool with rational curvature and obliquity can not only yield sound joint with small flashes and thickness reduction, but also prevent alclad from flowing into NZ, which has potential to weld thin alclad aluminum alloys. Meanwhile, the tensile strength and elongation of joint using the six-groove tool reach the maximum values of 362 MPa and 8.3%, up to 85.1% and 64% of BM.

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    Effect of Sheet Configuration on Microstructure and Mechanical Behaviors of Dissimilar Al-Mg-Si/Al-Zn-Mg Aluminum Alloys Friction Stir Welding Joints
    Yan Zhongjie,Liu Xuesong,Fang Hongyuan
    J. Mater. Sci. Technol., 2016, 32 (12): 1378-1385.  DOI: 10.1016/j.jmst.2016.10.011
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    Friction stir welding (FSW) was used to weld dissimilar Al-Mg-Si/Al-Zn-Mg aluminum alloys in this work. Influences of sheet configuration on microstructure and mechanical properties of the joints were mainly discussed. Results showed that rather different joint cross sections were obtained when using different sheet configurations. Coarser β' phases can be observed at the heat affected zone (HAZ) of the Al-Mg-Si alloy side, which was the main factor affecting the tensile properties and the fatigue properties. Tensile strengths of the dissimilar Al-Mg-Si/Al-Zn-Mg joints using both configurations were higher than that of the Al-Mg-Si FSW joint. When the Al-Zn-Mg alloy was located at the advancing side (AS), the joints owned better fatigue properties due to the bridging effect of the big secondary phase particles.

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    A Simulation Study on the Thermal Shock Behavior of Tungsten Mock-Up under Steady-State Heat Loads
    Wang Yanxin,Wang Shuming,Ye Qing,Yan Qingzhi,Ge Changchun
    J. Mater. Sci. Technol., 2016, 32 (12): 1386-.  DOI: 10.1016/j.jmst.2016.09.023
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    In a fusion reactor, due to high heat flux (HHF) loads, the plasma facing components (PFCs) will suffer severe thermal shock. In this paper, the temperature distribution and thermal-stress field of tungsten armor under HHF loads were investigated by the method of finite element modeling and simulating. The orthogonal experiment and range analysis were employed to compare the influence degree of four representative factors: steady-state heat flux; thickness of tungsten armor; inner diameter of cooling tube and the coefficient of convection heat transfer (CCHF) of cooling water, on thermal shock behavior tungsten mock-ups, and then get an optimization model to conduct the transient heat flux experiment. The final simulation results indicated that the steady-state heat flux and the thickness of W armor are the main influential factors for the maximum temperature of mock-ups. Furthermore, the influence of transient thermal shock all mainly concentrates on the shallow surface layer of tungsten (about 500 μm) under different transient heat flux (duration 0.5 ms). The results are useful for the structural design and the optimization of tungsten based plasma facing materials for the demonstration reactor (DEMO) or other future reactors.

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ISSN: 1005-0302
CN: 21-1315/TG
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