Started in 1985 Semimonthly
ISSN 1005-0302
CN 21-1315/TG
Impact factor:6.155

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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      15 February 2020, Volume 39 Issue 0 Previous Issue    Next Issue
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    Letter
    Effect of grain size on fatigue cracking at twin boundaries in a CoCrFeMnNi high-entropy alloy
    A.G. Wang, X.H. An, J. Gu, X.G. Wang, L.L. Li, W.L. Li, M. Song, Q.Q. Duan, Z.F. Zhang, X.Z. Liao
    J. Mater. Sci. Technol., 2020, 39 (0): 1-6.  DOI: 10.1016/j.jmst.2019.09.010
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    The fatigue cracking behavior at twin boundaries (TBs) in a CoCrFeMnNi high-entropy alloy with three different grain sizes was systematically investigated under low-cycle fatigue. Irrespective of grain size, the change from slip band cracking to TB cracking occurred with increasing the difference in the Schmid factors (DSF) between matrix and twin. However, the required critical DSF for the transition of the dominant cracking mode decreases with decreasing grain size due to the reduced slip band spacing that increases the impingement sites on the TBs and facilitates the coalescence of defects and voids to initiate TB cracks.

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    Research Article
    Deciphering deformation mechanisms of hierarchical dual-phase CrCoNi coatings
    S.J. Tsianikas, Y. Chen, Z. Xie
    J. Mater. Sci. Technol., 2020, 39 (0): 7-13.  DOI: 10.1016/j.jmst.2019.07.055
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    Hierarchical CrCoNi medium entropy alloy (MEA) thin films with a dual-phase face-centred cubic (FCC) and hexagonal closed-packed (HCP) nanostructure were prepared on M2 steel substrates by closed field unbalanced magnetron sputtering. Nanoindentation tests show an ultra-high hardness of 9.5 GPa, attributable to large amounts of innate planar defects (i.e., growth twins and stacking faults) impeding dislocation motion in the coatings. A deep analysis of undeformed and post-mortem samples reveals grain refinement as the dominant deformation mechanism in FCC dominated regions, while phase transformation and shear banding played major roles in regions occupied by HCP phase. The grain refinement was facilitated by twin/matrix lamellae, with dislocations piling up and arranging into interconnecting grain boundaries. The shear banding was accelerated by innate planar defects in the HCP phase due to a lack of slip systems. Of particular interest is the observation of HCP → FCC phase transformation, which was catalysed by deformation-induced grain reorientation with innate stacking faults acting as embryos to grow the FCC phase. The results of this work suggest that multiple deformation pathways could be activated in CrCoNi coatings with assistance of growth defects, thereby imparting these technically important coatings appreciable ductility.

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    Pressure-driven mold filling model of aluminum alloy melt/semi-solid slurry based on rheological behavior
    Zhen Ma, Huarui Zhang, Wei Song, Xiaoyan Wu, Lina Jia, Hu Zhang
    J. Mater. Sci. Technol., 2020, 39 (0): 14-21.  DOI: 10.1016/j.jmst.2019.07.048
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    The pressure-driven mold filling ability of aluminum alloy melt/semi-solid slurry is of great significance in pressure casting processes, and the rheological behavior of the alloy has a crucial effect on the mold filling ability according to fluid dynamics. In this work, a pressure-driven mold filling model is first proposed based on the rheological behavior of the alloys. A356 alloy is employed as an example to clarify the rheological behavior of aluminum alloys, which obeys the power law model and is affected by temperature. The rheological behavior of the alloy in semi-solid state is modelled with the coupling of shear rate and temperature. The stop of mold filling attributes to the pressure loss which is caused by the viscosity during the flow of the melt/semi-solid slurry. Pressure loss caused by viscous flow and heat transfer between the alloy and the mold are calculated and coupled during the mold filling of the melt/semi-solid slurry. A pressure-driven mold filling model of aluminum alloy melt/semi-solid slurry is established based on steady-state rheological behavior. The model successfully predicts the filling length of melt/semi-solid slurry in pressure casting processes. Compared with the experimental results, the model can provide a quantitative approach to characterize the pressure-driven mold filling ability of aluminum alloy melt. The model is capable of describing the stop filling behavior of other aluminum alloys in pressure casting processes with corresponding rheological parameters and heat transfer coefficient.

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    Scandium and phosphorus co-doped perovskite oxides as high-performance electrocatalysts for the oxygen reduction reaction in an alkaline solution
    Meigui Xu, Hainan Sun, Wei Wang, Yujuan Shen, Wei Zhou, Jun Wang, Zhi-Gang Chen, Zongping Shao
    J. Mater. Sci. Technol., 2020, 39 (0): 22-27.  DOI: 10.1016/j.jmst.2019.09.007
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    The requirement for a sustainable and renewable energy has inspired substantial interests in designing and developing earth-abundant and high-effectiveness electrocatalysts/electrodes for fuel cells and metal-air batteries, in which oxygen reduction reaction (ORR) plays a crucial role. Perovskite oxides have acquired rapid attention as ORR electrocatalysts to replace noble-metal-based catalysts owing to their intrinsic electrocatalytic activity, compositional and structural flexibility. Herein, we report a new Sc and P co-doped perovskite oxide (La0.8Sr0.2Mn0.95Sc0.025P0.025O3-δ, LSMSP) as an active and robust electrocatalyst for the ORR in an alkaline solution. LSMSP electrocatalyst shows superior ORR activity and stability than those of pristine La0.8Sr0.2MnO3-δ (LSM), Sc-doped LSM and P-doped LSM due to the optimized average valence of Mn ions, the large surface area, the smaller particle size and the synergetic effect introduced by the co-doping. Moreover, compared to the benchmark Pt/C electrocatalyst, LSMSP electrocatalyst displays comparable ORR activity and superior durability. These above results suggest that the co-doping strategy of Sc and P into perovskites is a useful method to design high-performance electrocatalysts for the ORR, which can be used in other electrocatalysis-based applications.

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    TiO2 nanotube arrays decorated with Au and Bi2S3 nanoparticles for efficient Fe3+ ions detection and dye photocatalytic degradation
    Jianying Huang, Jiali Shen, Shuhui Li, Jingsheng Cai, Shanchi Wang, Yao Lu, Jihuan He, Claire J.Carmalt, Ivan P.Parkin, Yuekun Lai
    J. Mater. Sci. Technol., 2020, 39 (0): 28-38.  DOI: 10.1016/j.jmst.2019.04.043
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    Due to increasingly serious environmental problems, many researchers are investigating green clean-energy to solve the world's energy supply issues. So the strategy that Au nanoparticles (Au NPs) and bismuth sulfide (Bi2S3) NPs are used to evenly decorate TiO2 nanotube arrays (TiO2 NTAs) was carried out. Composite materials demonstrated enhanced solar light absorption ability and excellent photoelectrochemical performance. This was attributed to the presence of Bi2S3 NPs with a narrow band gap and the decoration with noble metallic Au NPs which resulted in local surface plasmon resonance (LSPR) effects. The Au/Bi2S3@TiO2 NTAs composites exhibit improved photocatalytic activity for the degradation of methylene blue (MB) under irradiation of UV and visible light. Moreover, the Au/Bi2S3@TiO2 NTAs exhibits high fluorescence emission at 822 nm. Due to the better binding affinity between Bi2S3, TiO2 and Fe3+ ions, the synthesized nanocomposites exhibit high selectivity to Fe3+ ions. The number of binding sites for Au/Bi2S3@TiO2 NTAs was estimated to be 1.41 according to the double logarithmic regression method. The calculated value of “K” was 1862 M-1. Fluorescence emission intensity decreases with increasing concentration (30 μM-5000 μM). The detection limit of the synthesized sensor is 0.221 μM.

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    Assessment of structure integrity, corrosion behavior and microstructure change of AZ31B stent in porcine coronary arteries
    Shanshan Chen, Bin Zhang, Bin Zhanggchun, Hao Lin, Hui Yang, Feng Zheng, Ming Chen, Ke Yang
    J. Mater. Sci. Technol., 2020, 39 (0): 39-47.  DOI: 10.1016/j.jmst.2018.12.017
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    Magnesium alloy coronary stent becomes a hot research topic due to its biodegradable character for avoiding late thrombosis and late restenosis. However, fracture of Mg alloy stent was a common issue after implantation. In this study, 18 drug-eluting biodegradable AZ31B stents were implanted into porcine coronary arteries to assess its structural integrity, corrosion behavior and microstructure change in vivo. The coronary artery tissue responses to AZ31B stent implantation were detected by quantitative coronary angiography and optical coherence tomography at the set time periods. In addition, further analyses were focused on the stent structure integrity, corrosion behaviors and the microstructure change of Mg alloy stents after implantation. A large number of fractures on stent struts were observed by high-resolution transmission X-ray tomography clearly. Moreover, degradation products, twins and grain refinement that appeared in Mg alloy stent matrix after implantation were also observed during the study. Inferred from this study, it is shown that the loss of AZ31B stent structural integrity may be the result of stress concentration, degradation and microstructure change.

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    Effects of N-alkylation on anticorrosion performance of doped polyaniline/epoxy coating
    Suyun Liu, Li Liu, Ying Li, Fuhui Wang
    J. Mater. Sci. Technol., 2020, 39 (0): 48-55.  DOI: 10.1016/j.jmst.2019.06.012
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    N-alkylation of sulfosalicylic acid-doped polyaniline (PANI-SSA) was used to promote the anticorrosion performance of PANI-SSA/epoxy coating for 5083 Al alloy. PANI-SSA was modified with C5H11Br and C12H25Br in polar solvents IPA (isopropanol) and DMF (dimethylformamide), and then characterized by FTIR, XPS and sedimentation experiments. Results showed that alkanes were successfully linked onto the PANI-SSA chains. The compatibility between N-alkylated PANI-SSA and epoxy/xylene solution was improved. SEM results proved a better dispersion performance of N-alkylated PANI-SSA in epoxy coatings, with less holes and aggregations. Corrosion protection of the epoxy coatings incorporating PANI-SSA and N-alkylated PANI-SSA on 5083 Al alloy was studied by EIS and adhesion measurements in 3.5% NaCl solution. It turned out that the epoxy coating including C12H25Br-modified PANI-SSA in DMF has yielded the highest values of impedance modulus and best protective properties.

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    Invited Review
    Deformation behavior and microstructure evolution of titanium alloys with lamellar microstructure in hot working process: A review
    Pengfei Gao, Mingwang Fu, Mei Zhan, Zhenni Lei, Yanxi Li
    J. Mater. Sci. Technol., 2020, 39 (0): 56-73.  DOI: 10.1016/j.jmst.2019.07.052
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    Titanium alloys have been widely used in many industrial clusters such as automotive, aerospace and biomedical industries due to their excellent comprehensive properties. In order to obtain fine microstructures and favorable properties, a well-designed multi-step thermomechanical processing (TMP) is critically needed in manufacturing of titanium components. In making of titanium components, subtransus processing is a critical step to breakdown lamellar microstructure to fine-structure in hot working process and thus plays a key role in tailoring the final microstructure and properties. To realize this goal, huge efforts have been made to investigate the mechanisms of microstructure evolution and flow behavior during the subtransus processing. This paper reviews the recent experimental and modelling progresses, which aim to provide some guidelines for the process design and microstructure tailoring for titanium alloy research community. The characteristics of the initial lamellar microstructure are presented, followed by the discussion on microstructure evolution during subtransus processing. The globularization of lamellar α is analyzed in detail from three aspects, i.e., globularization mechanism, heterogeneity and kinetics. The typical features of flow behaviors and the explanations of significant flow softening are then summarized. The recent advances in modelling of microstructure evolution and flow behaviors in the subtransus processing are also articulated. The current tantalized issues and challenges in understanding of the microstructure evolution and flow behaviors of the titanium alloys with lamellar microstructure are presented and specified in future exploration of them.

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    Research Article
    Cyclic shear deformation and fatigue of extruded Mg-Gd-Y magnesium alloy
    Fenghua Wang, Miaolin Feng, Yanyao Jiang, Jie Dong, Zhenyan Zhang
    J. Mater. Sci. Technol., 2020, 39 (0): 74-81.  DOI: 10.1016/j.jmst.2019.08.025
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    Deformation and fatigue of extruded Mg-8.0Gd-3.0Y-0.5Zr (GW83, wt%) magnesium (Mg) alloy were experimentally investigated under cyclic torsion using tubular specimen fabricated along the extrusion direction. The controlled shear strain amplitudes ranged from 0.606% to 4.157%. Twinning and detwinning of extension twins are observed to take place during cyclic torsion and the shear stress-shear strain hysteresis loops display a perfectly symmetric shape at all tested strain amplitudes. Marginal cyclic softening is observed when the shear strain amplitude is higher than 1.732%. The strain-life fatigue curve shows two kink points, corresponding to the shear strain amplitude of 1.040% and 1.732%, respectively. When the shear strain amplitude is higher than the upper kink point, early fatigue crack is found to initiate on the maximum shear plane. When the strain amplitude is lower than the lower kink point, fatigue cracking is parallel to the maximum tensile plane. At an identical equivalent strain amplitude, the fatigue life under pure shear is much higher than that under tension-compression. The fatigue life of extruded GW83 alloy is much higher than that of extruded AZ31B alloy at the same plastic strain energy density.

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    In situ synthesis of a porous high-Mn and high-Al steel by a novel two-step pore-forming technique in vacuum sintering
    Chuanbing Zhuang, Zhigang Xu, Shangyu Huang, Yu Xia, Chuanbin Wang, Qiang Shen
    J. Mater. Sci. Technol., 2020, 39 (0): 82-88.  DOI: 10.1016/j.jmst.2019.09.008
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    In this work, a novel in-situ two-step pore-forming process in vacuum sintering (ITPVS) technique combining low-temperature processing to produce open pores through the interdiffusion among the intrinsic components in the base steel, and subsequent high-temperature processing to further improve the porosities by the sublimation of Mn via previously formed open pores, was proposed to produce a lab-scale porous FeMnAl steel. For the first time, a high-Mn and high-Al steel with open and overall porosities of ~59.6 vol.% and ~63.7 vol.% (percent in volume, vol.%) was synthesized by isothermal holding of the quaternary elemental Fe/Mn/Al/C powder mixture at 640 ℃ for 1 h and the subsequent sintering at 1200 ℃ for 1 h. Elemental Al partly incorporated into/reacted with α-Fe and α-Mn after sintering at 640 ℃ for 1 h, leading to the overall and open porosities promoting by ~26.6 vol.% and ~25.6 vol.%. After sintering at 1200 ℃, FeMnAl steel with increased porosities mainly comprising of austenite and α-Fe obtained. The compression strength and corresponding strain of the 1200 ℃-sintered porous specimen without crack on the surface was ~75 MPa and ~25%. The ITPVS technique takes advantage of using the intrinsic components like Al, Mn and Fe in steels to produce porous structure. This is beneficial to avoiding the contamination of the FeMnAl steel matrix caused by the employment of the foreign pore-forming agents.

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    Performance of GH4169 brazed joint using a new designed nickel-based filler metal via cluster-plus-glue-atom model
    Honggang Dong, Yueqing Xia, Xinxing Xu, Gul Jabeen Naz, Xiaohu Hao, Peng Li, Jun Zhou, Chuang Dong
    J. Mater. Sci. Technol., 2020, 39 (0): 89-98.  DOI: 10.1016/j.jmst.2019.08.028
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    A novel Ni-Cr-Si-B filler metal with the cluster formula of [Cr-Ni12]B2Cr + [B-Ni8Cr]BSiCr based on the cluster-plus-glue-atom model was designed for vacuum brazing GH4169 alloy. The effect of brazing temperature and brazing time on microstructure and shear strength of GH4169 alloy joints was investigated. The brazed seam was mainly composed of γ-Ni solid solution. (Nb, Ti)-rich phase and (Cr, Nb, Mo)-rich borides distributed in diffusion zones. The diffusion and aggregation of B, Cr, Nb, and Mo resulted in the variation of phase contrast and morphology of borides. Coarse precipitations in the joint brazed at 1240 ℃ consisted of borides, Laves phase and δ phase. The shear strength of joints was principally dominated by the brittle precipitations in diffusion zone, and the homogenization of microstructure improved the room-temperature shear strength to 820 MPa with the high-temperature shear strength of 627 MPa for the joint brazed at 1240 ℃/20 min. The joint fractured in diffusion zone and brazed seam, and the existence of borides and Laves phase in diffusion zone provide the potential origin for crack growth.

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    Microstructure and mechanical properties of (TiZrNbTaMo)C high-entropy ceramic
    Kai Wang, Lei Chen, Chenguang Xu, Wen Zhang, Zhanguo Liu, Yujin Wang, Jiahu Ouyang, Xinghong Zhang, Yudong Fu, Yu Zhou
    J. Mater. Sci. Technol., 2020, 39 (0): 99-105.  DOI: 10.1016/j.jmst.2019.07.056
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    A high-entropy (TiZrNbTaMo)C ceramic has been successfully fabricated by hot pressing the newly-synthesized quinary carbide powder to investigate its microstructure and mechanical properties. The carbothermal reduction process of equimolar quinary metallic oxides at 1500 ℃ for 1 h generates a carbide powder mixture, which consists mainly of TaC- and ZrC-based solid solutions. The as-synthesized powder was then sintered to form a single-phase high-entropy ceramic by a two-step hot pressing at 1850 ℃ for 1 h and 2100 ℃ for 0.5 h, respectively. The high-entropy ceramic exhibits a fine grain size of about 8.8 μm, a high compositional uniformity and a high relative density of 98.6% by adding Mo as the strategic main component. The measured nanohardness values of (TiZrNbTaMo)C ceramic are 25.3 GPa at 9.8 N and 31.3 GPa at 100 mN, respectively, which are clearly higher than those of other available high-entropy carbide ceramics.

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    Weak-reduction graphene oxide membrane for improving water purification performance
    Hao Yu, Yi He, Guoqing Xiao, Yi Fan, Jing Ma, Yixuan Gao, Ruitong Hou, Jingyu Chen
    J. Mater. Sci. Technol., 2020, 39 (0): 106-112.  DOI: 10.1016/j.jmst.2019.08.024
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    Two-dimensional (2D) materials are promising candidates for advanced water purification membranes. In this work, UV reduced GO (UrGO) membranes on the support of polyvinylidene fluoride (PVDF) had been fabricated for wastewater treatment. The reduction degree of GO membrane on the effect of water purification performance was investigated, and it was found that the weak-reduction GO membrane exhibited the optimal performance of removing pollutant from wastewater than GO membrane. Besides, scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectra and contact angle tests were used to characterize the physical and chemical properties of the UrGO membranes, and the permeance and rejection ability of the as-prepared filtration membranes were determined. Due to the weak-reduction of GO, pristine graphitic sp2 domains increased with slightly decreasing D-spacing. Thus, the UrGO membrane showed a higher water flux of 38.27 L m-2 h-1 bar-1, which was improved more than 270% compared to GO membrane, and dyes rejection increased. Those outstanding performances indicated that the UrGO membrane could effectively regulate the contradiction of the trade-off balance between flux and rejection, and hold great potential in real-world waste-water purification.

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    In-situ observation of solid-liquid interface transition during directional solidification of Al-Zn alloy via X-ray imaging
    Yuanhao Dong, Sansan Shuai, Tianxiang Zheng, Jiawei Cao, Chaoyue Chen, Jiang Wang, Zhongming Ren
    J. Mater. Sci. Technol., 2020, 39 (0): 113-123.  DOI: 10.1016/j.jmst.2019.06.026
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    The morphological instability of solid/liquid (S/L) interface during solidification will result in different patterns of microstructure. In this study, two dimension (2D) and three dimension (3D) in-situ observation of solid/liquid interfacial morphology transition in Al-Zn alloy during directional solidification were performed via X-ray imaging. Under a condition of increasing temperature gradient (G), the interface transition from dendritic pattern to cellular pattern, and then to planar growth with perturbation was captured. The effect of solidification parameter (the ratio of temperature gradient and growth velocity (v), G/v) on morphological instabilities was investigated and the experimental results were compared to classical “constitutional supercooling” theory. The results indicate that 2D and 3D evolution process of S/L interface morphology under the same thermal condition are different. It seems that the S/L interface in 2D observation is easier to achieve planar growth than that in 3D, implying higher S/L interface stability in 2D thin plate samples. This can be explained as the restricted liquid flow under 2D solidification which is beneficial to S/L interface stability. The in-situ observation in present study can provide coherent dataset for microstructural formation investigation and related model validation during solidification.

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    Effect of Y and Ce on the microstructure, mechanical properties and anisotropy of as-rolled Mg-8Li-1Al alloy
    Feng Zhong, Huajie Wu, Yunlei Jiao, Ruizhi Wu, Jinghuai Zhang, Legan Hou, Milin Zhang
    J. Mater. Sci. Technol., 2020, 39 (0): 124-134.  DOI: 10.1016/j.jmst.2019.04.045
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    The effects of combined addition of Y and Ce on the microstructure, mechanical properties and anisotropy of as-rolled Mg-8Li-1Al (LA81) alloy were studied. The combined addition of Y and Ce improves the mechanical properties with a low plasticity loss by solution strengthening, dispersion strengthening, grain refinement strengthening. Mg-8Li-1Al-0.6Y-0.6Ce (LA81-0.6Y-0.6Ce) has better mechanical properties and shows an almost isotropy. It possesses an ultimate tensile strength of 278.7 MPa and an elongation of 15.0%. Compared to LA81 alloy, the ultimate tensile strength increases by about 17.6% with an elongation reduction of only 3.5%, and a good isotropy of ultimate tensile strength and elongation (the value of ravg is near 1).

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    Improvement of elevated-temperature strength and recrystallization resistance via Mn-containing dispersoid strengthening in Al-Mg-Si 6082 alloys
    Chen Li, Kun Liu, X.-Grant Chen
    J. Mater. Sci. Technol., 2020, 39 (0): 135-143.  DOI: 10.1016/j.jmst.2019.08.027
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    The precipitation behavior of Mn-containing dispersoids in Al-Mg-Si 6082 alloys with different Mn contents (0, 0.5 and 1.0 wt%) during various heat treatments (300-500 ℃) was investigated. The effects of dispersoids on elevated-temperature strength and recrystallization resistance during hot-rolling and post-rolling annealing were evaluated. The results showed that the dispersoids in the Mn-containing alloys (0.5 and 1.0%) began to precipitate at 350 ℃ and reached the optimum conditions after 2-4 h at 400 ℃. However, the dispersoids coarsened with increasing holding time at temperatures above 450 ℃. After the peak precipitation treatment at 400 ℃ for 2 h, the yield strength at 300 ℃ increased from 28 MPa (base alloy free of Mn) to 55 MPa (alloy with 0.5% Mn) and 70 MPa (alloy with 1% Mn), respectively, demonstrating a significant dispersoid strengthening effect at elevated temperature. In addition, the dispersoids were thermally stable at 300 ℃ for up to 1000 h holding owing to its relative high precipitation temperature (350-400 ℃), leading to the superior constant mechanical performance at elevated temperature during the long service life. During hot rolling and post-rolling annealing, the presence of a large amount of dispersoids results in the higher Zener drag PZ compared with base alloy and then significantly improved the recrystallization resistance. The alloy containing 0.5% Mn exhibited the highest recrystallization resistance among three experimental alloys studied during the post-rolling process, likely resulted from the lower coarsening rate of dispersoids and the lower dispersoids free zone.

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    Cracking behavior and control of β-solidifying Ti-40Al-9V-0.5Y alloy produced by selective laser melting
    Piao Gao, Wenpu Huang, Huihui Yang, Guanyi Jing, Qi Liu, Guoqing Wang, Zemin Wang, Xiaoyan Zeng
    J. Mater. Sci. Technol., 2020, 39 (0): 144-154.  DOI: 10.1016/j.jmst.2019.08.026
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    A β-solidifying Ti-40Al-9V-0.5Y (at.%) alloy with a high cracking sensitivity has been successfully fabricated by selective laser melting (SLM) in this study. The influence factors for cracking sensitivity, cracking behavior and crack inhibition mechanism were investigated. The results show that the effects of process parameters on cracking sensitivity strongly depend on the cooling rate in molten pool with different heat transfer modes. The conduction mode with higher cooling rates exhibits a higher cracking sensitivity in comparison to the keyhole mode. Microstructure characteristics and phase transformations controlled by cooling rate determine the inherent ductility of β-solidifying γ-TiAl alloys during SLM. On this basis, the formation and inhibition mechanism of solidification and cold cracking are proposed. Finally, the crack-free Ti-40Al-9V-0.5Y sample with fine equiaxed microstructures and favorable mechanical properties (microhardness of 542 ± 19 HV, yield strength of 1871 ± 12 MPa, ultimate strength of 2106 ± 13 MPa and ultimate compressive strain of 10.89 ± 0.57%) can be produced by SLM. The strengthening mechanism can be attributed to grain refinement and precipitation strengthening.

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    3D hierarchical NiS2/MoS2 nanostructures on CFP with enhanced electrocatalytic activity for hydrogen evolution reaction
    Jieqiong Wang, Zheng Liu, Changhong Zhan, Kexi Zhang, Xiaoyong Lai, Jinchun Tu, Yang Cao
    J. Mater. Sci. Technol., 2020, 39 (0): 155-160.  DOI: 10.1016/j.jmst.2019.05.037
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    The electrocatalytic activity for hydrogen evolution reaction (HER) is strongly correlated with active edge sites and resulting efficient charge transport capability. Here, we presented a facile two-step method to synthesize 3D hierarchical NiS2/MoS2 composite nanostructures on a carbon fiber paper (CFP) skeleton. The nanostructures distributed on CFP uniformly and composed of 2D nanosheets, which would provide plenty of active edge sites and increase the HER activity. Electrochemical measurement suggests that the prepared NiS2/MoS2 exhibit great HER activity including a low overpotential of 102 mV, a small Tafel slope of 67 mV/dec, and a high double-layer capacity of 53.7 mF/cm2 in 1 M KOH aqueous solution. In addition, the HER activity is almost unchanged after galvanostatic technique with applied current densities of 10 mA/cm2 for 20 h.

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    Theoretical investigation on the stability, mechanical and thermal properties of the newly discovered MAB phase Cr4AlB4
    Fu-Zhi Dai, Haiming Zhang, Huimin Xiang, Yanchun Zhou
    J. Mater. Sci. Technol., 2020, 39 (0): 161-166.  DOI: 10.1016/j.jmst.2019.01.017
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    The nanolaminated MAB phases have attracted great research interests in recent years due to their similarities to MAX phases, which display both metallic and ceramic-like properties. In the present work, a newly discovered MAB phase Cr4AlB4 was investigated by first principles calculations. Energy evaluations indicate that Cr4AlB4 can be synthetized in Al lean condition, which can further transform to Cr2AlB2 in Al rich condition. The full set of elastic properties and their dependences on temperature, ideal strengths under different tensile and shear deformations, and thermal expansions of Cr4AlB4 were predicted. The results reveal that the properties of Cr4AlB4 are dominated by the layered crystal structure and weak bonding nature between Al and Cr2B2 layers, including low elastic stiffness and large thermal expansion along [010] direction (the stacking direction of Al and Cr2B2 layers), low shear resistances in (010) plane, and preferentially cleavage along and/or shear in (010) plane. Therefore, it suggests that Cr4AlB4 displays similar mechanical properties to MAX phases, including readily machinable, thermal shock resistant, and damage tolerant. In combination with the fact that Cr, Al and B all can form dense oxides to protect the material from further oxidation, Cr4AlB4 is regarded as a promising high temperature ceramic.

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    Letter
    (Y0.25Yb0.25Er0.25Lu0.25)2(Zr0.5Hf0.5)2O7: A defective fluorite structured high entropy ceramic with low thermal conductivity and close thermal expansion coefficient to Al2O3
    Zifan Zhao, Heng Chen, Huimin Xiang, Fu-Zhi Dai, Xiaohui Wang, Wei Xu, Kuang Sun, Zhijian Peng, Yanchun Zhou
    J. Mater. Sci. Technol., 2020, 39 (0): 167-172.  DOI: 10.1016/j.jmst.2019.08.018
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    Research Article
    Microstructure and high temperature fracture toughness of NG-TIG welded Inconel 617B superalloy
    Xiaogang Li, Kejian Li, Shanlin Li, Yao Wu, Zhipeng Cai, Jiluan Pan
    J. Mater. Sci. Technol., 2020, 39 (0): 173-182.  DOI: 10.1016/j.jmst.2019.07.021
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    In the present study, the microstructure, fracture toughness, and fracture behavior of Inconel 617B narrow gap tungsten inert gas (NG-TIG) welded joint were investigated systematically at the designed service temperature of 700 ℃. Fracture toughness (J0.2) of base metal (BM) and heat affected zone (HAZ) was higher than that of weld metal (WM). In HAZ and BM, strain mainly localised at grain boundaries with large misorientation and there were lots of coincidence site lattice (CSL) ∑3 boundaries related to twins inside grains, which led to the much higher fracture toughness of BM and HAZ than WM. The high numbers of twins as well as the less serious strain localization at grain boundaries resulted in the most outstanding fracture toughness of BM.

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    Deciphering deformation mechanisms of hierarchical dual-phase CrCoNi coatings
    S.J. Tsianikas, Y. Chen, Z. Xie
    J. Mater. Sci. Technol., 2020, 39 (0): 183-189.  DOI: 10.1016/j.jmst.2019.07.047
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    Hierarchical CrCoNi medium entropy alloy (MEA) thin films with a duaerarchical CrCoNi medium entropy alloy (MEA) thin films with a dual-phase face-centred cubic (FCC) and hexagonal closed-packed (HCP) nanostructure were prepared on M2 steel substrates by closed field unbalanced magnetron sputtering. Nanoindentation tests show an ultra-high hardness of 9.5 GPa, attributable to large amounts of innate planar defects (i.e., growth twins and stacking faults) impeding dislocation motion in the coatings. A deep analysis of undeformed and post-mortem samples reveals grain refinement as the dominant deformation mechanism in FCC dominated regions, while phase transformation and shear banding played major roles in regions occupied by HCP phase. The grain refinement was facilitated by twin/matrix lamellae, with dislocations piling up and arranging into interconnecting grain boundaries. The shear banding was accelerated by innate planar defects in the HCP phase due to a lack of slip systems. Of particular interest is the observation of HCP → FCC phase transformation, which was catalysed by deformation-induced grain reorientation with innate stacking faults acting as embryos to grow the FCC phase. The results of this work suggest that multiple deformation pathways could be activated in CrCoNi coatings with assistance of growth defects, thereby imparting these technically important coatings appreciable ductility.

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    Evolution of rust layers on carbon steel and weathering steel in high humidity and heat marine atmospheric corrosion
    Yueming Fan, Wei Liu, Shimin Li, Thee Chowwanonthapunya, Banthukul Wongpat, Yonggang Zhao, Baojun Dong, Tianyi Zhang, Xiaogang Li
    J. Mater. Sci. Technol., 2020, 39 (0): 190-199.  DOI: 10.1016/j.jmst.2019.07.054
    Abstract   HTML   PDF

    The evolution of the rust layers on carbon steel and weathering steel in high humidity and heat marine atmospheric environment was investigated by wet/dry cyclic acceleration corrosion tests in this study. The corrosion process of carbon steel and weathering steel was divided into two stages and the reasons for the changes in the corrosion rates of two steels were different. The composition phase of the inner rust layer of weathering steel was mainly goethite, whereas that of carbon steel was mainly akaganeite. Rust resistance (Rr) performed better than charge transfer resistance (Rt) in evaluating the protection performance of rust layer. As the corrosion proceeded, the evolution of the cathodic process of weathering steel was not obvious, whereas that of carbon steel was irregular.

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