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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      20 November 2018, Volume 34 Issue 11 Previous Issue    Next Issue
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    Orginal Article
    Application of materials based on group VB elements in sodium-ion batteries: A review
    Menglei Sun, Yu Jiang, Jiangfeng Ni, Liang Li
    J. Mater. Sci. Technol., 2018, 34 (11): 1969-1976.  DOI: 10.1016/j.jmst.2018.04.007
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    Owing to their high redox activity, abundant resource, and low cost, compounds based on group VB elements (V, Nb, and Ta) are promising electrode materials for an array of energy storage devices. Moreover, their open structure benefits transportation and accommodation of alkali Na+ ions, rending them particularly appealing for cost-effective sodium-ion batteries (SIBs). In the last decade, these materials have evoked intensive investigations in SIBs, serving as either cathode, anode, or both depending on their sodiation degree and redox potential. Exciting progress has been made, but significant gaps in our knowledge still remain. Their practical application in SIBs remains unclear and thus calls for further efforts to settle several technical challenges in terms of poor conductivity, unstable cycling, and inefficient charge storage. In this perspective, a brief overview is given of recent progress on how to solve these technical issues and envision their bright future in SIBs, which may serve as a source to inspire researches on relevant topics.

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    Oxidation of amorphous alloys
    Zhiqiang Xu, Yifei Xu, An Zhang, Jiangyong Wang, Zumin Wang
    J. Mater. Sci. Technol., 2018, 34 (11): 1977-2005.  DOI: 10.1016/j.jmst.2018.02.015
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    Owing to their unique short- or medium-range ordered microstructures and excellent mechanical, physical, and chemical properties, amorphous alloys have attracted significant interest in recent years. For the application of amorphous alloys, clarifying their oxidation processes and mechanisms is necessary since many of the surface-related properties of amorphous alloys largely depend on the surface oxide layer. The aim of this paper is to review the recent research on the thermal oxidation behaviors of amorphous alloys under pure oxygen or air condition. The contents are divided into three categories according to the number of components the research considers, i.e., the oxidation of binary, ternary, and multi-component (>3) amorphous alloys. Each section discusses the thermal stability of the amorphous matrix, oxidation kinetics, and the oxide layer and amorphous substrate, which are strongly affected by internal factors (i.e., alloy elements and microstructure) and external factors (i.e., oxidation temperature, duration, and oxygen partial pressure, etc.). The general features of the oxidation of amorphous alloys - from simple binary to complex multi-component amorphous alloys - will be summarized. This overview of the current scientific understanding on the fundamentals of these materials may provide guidelines for the development of strongly corrosion-resistant amorphous alloys.

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    Thermoplastic micro-formability of TiZrHfNiCuBe high entropy metallic glass
    Xinyun Wang, Wenlei Dai, Mao Zhang, Pan Gong, Ning Li
    J. Mater. Sci. Technol., 2018, 34 (11): 2006-2013.  DOI: 10.1016/j.jmst.2018.04.006
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    High entropy metallic glasses (MGs) have attracted tremendous attentions owing to high entropy that benefits the probing of new MG-forming systems. However, the micro-formability of high entropy MGs is lack of investigation in comparison with these conventional MG counterparts, which is crucial to the development of this kind of metallic alloys. In this work, the thermoplastic mciro-formability of TiZrHfNiCuBe high entropy MG was systemically investigated. Time-Temperature-Transformation (TTT) curve was first constructed based on isothermal crystallization experiments, which provides thermoplastic processing time of the supercooled high entropy MGs. By comparison with the deformation map, Newtonian flow was found beneficial to the thermoplastic formability. While the thermoplastic forming becomes arduous with reducing mould size to tens micrometer, because of the strong supercooled TiZrHfNiCuBe high entropy MG (fragility = 27). Fortunately, the micro-formability of TiZrHfNiCuBe high entropy MG could be improved by vibration loading, as demonstrated by finite-element-method simulation. Our findings not only systemically evaluate the thermoplastic micro-formability of high entropy MG, but also provide fundamental understanding of the phenomenon.

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    Effect of alloying elements on microstructure, mechanical and damping properties of Cr-Mn-Fe-V-Cu high-entropy alloys
    Ruokang Song, Fan Ye, Chenxi Yang, Sujun Wu
    J. Mater. Sci. Technol., 2018, 34 (11): 2014-2021.  DOI: 10.1016/j.jmst.2018.02.026
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    A series of new Cr-Mn-Fe-V-Cu high-entropy alloys were prepared by arc melting and suction casting. It is found that with the addition of Cu, the structure of the alloys evolved from BCC + BCC1 phases to BCC + FCC phases. With increase of Cu, the volume fraction of the Cu-Mn-rich FCC phase increased, and the morphology of the FCC phase transformed from granular particles to long strips and blocks. Compared with other reported HEAs, the Cr-Mn-Fe-V-Cu HEAs exhibit a good balance between strength and ductility. The CrMn0.3FeVCu0.06 alloy with granular FCC particles exhibits the highest compressive yield strength (1273 MPa) and excellent ductility (εf = 50.7%). Quantitative calculations for different strengthening mechanisms demonstrate that dislocation and precipitate strengthening are responsible for high strength of the CrMn0.3FeVCu0.06 alloy, while the solid solution strengthening effect is very low because of its small atomic-size difference. In addition, the CrMn0.3FeVCu0.06 alloy exhibits good damping capacity due to its high dislocation and interface damping effects. Therefore, the dislocation density and distribution of FCC phase are the crucial factors for improvement of both mechanical properties and damping capacity of the HEAs.

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    First demonstration of possible two-dimensional MBene CrB derived from MAB phase Cr2AlB2
    Haiming Zhang, Huimin Xiang, Fu-zhi Dai, Zhili Zhang, Yanchun Zhou
    J. Mater. Sci. Technol., 2018, 34 (11): 2022-2026.  DOI: 10.1016/j.jmst.2018.02.024
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    In this communication, the possibility for the preparation of two-dimensional MBene CrB from MAB phase Cr2AlB2 is demonstrated for the first time. Herein M is a transition metal, A is a group IIIA or IVA element and B is boron; MAB phases are layered transition metal ternary borides, MBene is used to emphasize the loss of A group element from the parent MAB phases and to highlight the 2D nature. The possible 2D CrB nano sheets are prepared by selectively etching out Al layers from Cr2AlB2 by immersing the Cr2AlB2 powders in dilute HCl solution at room temperature. The as-prepared 2D CrB nano sheets are examined using X-ray diffraction and scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS). In addition, different structure models are built to explain the observed phenomena. The discovery in this work opens a door to the synthesis of a large number of new 2D MBenes from MAB phases.

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    Revealing the atomistic deformation mechanisms of face-centered cubic nanocrystalline metals with atomic-scale mechanical microscopy: A review
    Duohui Li, Xinyu Shu, Deli Kong, Hao Zhou, Yanhui Chen
    J. Mater. Sci. Technol., 2018, 34 (11): 2027-2034.  DOI: 10.1016/j.jmst.2018.03.006
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    Nanocrystalline metals have many functional and structural applications due to their excellent mechanical properties compared to their coarse-grained counterparts. The atomic-scale understanding of the deformation mechanisms of nanocrystalline metals is important for designing new materials, novel structures and applications. The review presents recent developments in the methods and techniques for in situ deformation mechanism investigations on face-centered-cubic nanocrystalline metals. In the first part, we will briefly introduce some important techniques that have been used for investigating the deformation behaviors of nanomaterials. Then, the size effects and the plasticity behaviors in nanocrystalline metals are discussed as a basis for comparison with the plasticity in bulk materials. In the last part, we show the atomic-scale and time-resolved dynamic deformation processes of nanocrystalline metals using our in-lab developed deformation device.

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    Effects of holding time and Zener-Hollomon parameters on deformation behavior of cast Mg-8Gd-3Y alloy during double-pass hot compression
    Xi Nie, Shuai Dong, Fenghua Wang, Li Jin, Jie Dong
    J. Mater. Sci. Technol., 2018, 34 (11): 2035-2041.  DOI: 10.1016/j.jmst.2018.03.001
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    Double-pass hot compression tests were carried out over a wide range of holding time (0-180 s) and Zener-Hollomon parameter (1.6E15-1.3E20) to study the deformation behavior of cast Mg-8Gd-3Y alloy. The flow curves show obvious work hardening and strain softening stages, leading to the peak stress of double-pass hot compression. Holding time and Zener-Hollomon parameter can significantly affect the second pass peak stress. It is found that increasing the holding time can cause a higher peak stress in the second pass deformation. The second pass stress reaches the peak stress of 71 MPa at Zener-Hollomom parameter of 1.6E15. When the parameter rises to 1.3E20, the second pass peak goes up to 237 MPa. In addition, the second pass peak stress is significantly higher than the unloading stress, which is opposite to the flow behavior of aluminum alloys. Residual stored deformation energy caused by the first pass deformation could be consumed by metadynamic recrystallization. Therefore, more strain energy is required for subsequent dynamic recrystallization, resulting in hardening behavior. A hardening fraction is defined to describe the deformation behavior quantitatively, which shows a positive correlation with the metadynamic recrystallization fraction. The metadynamic recrystallization leads to grain growth at the inter pass holding stage, diminishing dynamic recrystallization nucleation positions in the second pass deformation.

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    Weakened anisotropy of mechanical properties in rolled ZK60 magnesium alloy sheets with elevated deformation temperature
    Wenke Wang, Wenzhen Chen, Wencong Zhang, Guorong Cui, Erde Wang
    J. Mater. Sci. Technol., 2018, 34 (11): 2042-2050.  DOI: 10.1016/j.jmst.2018.02.019
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    The rolling direction (RD) and the transverse direction (TD) samples were obtained from an as-rolled ZK60 magnesium alloy sheet with strong anisotropy of initial texture and their mechanical properties were tested at various deformation temperatures. Meanwhile, the microstructure and texture of these samples after fracture were investigated. Results revealed that a higher flow stress along the RD than that along the TD at room temperature were ascribed to the strong anisotropy of transitional texture, and this texture effect was remarkably weakened with the increase of deformation temperature. Deformation structure was dominant at 100 °C, and was replaced by dynamic recrystallization structure when the deformation temperature increased to 200 °C and 300 °C. The texture presented a strong texture (transitional texture in the RD sample and basal texture in the TD sample) at 100 °C, but its intensity visibly decreased and texture components became more disperse at 200 °C and 300 °C. These microstructure and texture results were employed in conjunction with calculated results to argue that raising deformation temperature could increase the activity of non-basal slip by tailoring the relative critical resolved shear stress of each deformation mode and finally result in low texture effect on mechanical anisotropy.

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    Optimum rolling speed and relevant temperature- and reduction-dependent interfacial friction behavior during the break-down rolling of AZ31B alloy
    Weitao Jia, Yan Tang, Fangkun Ning, Qichi Le, Lei Bao
    J. Mater. Sci. Technol., 2018, 34 (11): 2051-2062.  DOI: 10.1016/j.jmst.2018.03.020
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    The present study aimed to determine the optimum rolling speed for break-down rolling of as-cast AZ31B alloy and investigated the friction behavior associated with temperature- and reduction-sensitivity at the roll/plate contact interface. Tensile testing, formability evaluation and microstructural studies relevant to different rolling speeds were performed and finally the optimum operating rolling speed (50.0 ± 0.8 m/min) was obtained. Further, the effects of rolling reduction and initial temperature were assessed on the temperature variation, lateral spread and interfacial friction behavior at optimum rolling speed. The results showed that lower rolling speed (18.0 ± 0.8 m/min) resulted in an incompletely recrystallized structure where twins occupied relatively high volume fraction. Twinning dominated the deformation at rolling speed exceeding the optimum, resulting in the local recrystallization with shear bands and coarse grains. Rolling at 50.0 ± 0.8 m/min could get the best overall tensile properties and rolling formability due to the relatively high recrystallization degree and microstructure uniformity. An inverse method has been developed to determine the interfacial friction coefficient during interaction of AZ31B alloy with roll surfaces. When rolling at the optimum speed, the interfacial friction coefficient ranged from 0.16 to 0.58, which was strongly positively correlated with the reduction but slightly positively correlated with the initial temperature. Depended on the rolling characteristics, external friction effect coefficient ranged from 1.25 to 2.35 and it exhibited positive correlation with both the initial rolling temperature and rolling reduction.

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    Development of non-flammable high strength extruded Mg-Al-Ca-Mn alloys with high Ca/Al ratio
    Guosong Han, Ding Chen, Gang Chen, Jianghua Huang
    J. Mater. Sci. Technol., 2018, 34 (11): 2063-2068.  DOI: 10.1016/j.jmst.2018.03.019
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    A series of non-flammable high strength Mg-Al-Ca-Mn alloys with high Ca/Al ratio were fabricated by water-cooled casting and hot extrusion. Microstructure and mechanical properties were investigated to study the effect of hot extrusion. The experimental results showed that hot extrusion significantly improved the mechanical properties by grain refinement and precipitates. Ignition temperature was measured by furnace test, and the highest temperature is up to approximately 1040 °C due to the composite oxide layer consisting of CaO and MgO. In addition, a laboratory-scale flame test was conducted to evaluate the flammability of smaller specimens. These alloys exhibited marvelous flame resistance attributed to the protective effect of dense and stable oxide film.

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    Role of pre-vertical compression in deformation behavior of Mg alloy AZ31B during super-high reduction hot rolling process
    Weitao Jia, Qichi Le, Yan Tang, Yunpeng Ding, Fangkun Ning, Jianzhong Cui
    J. Mater. Sci. Technol., 2018, 34 (11): 2069-2083.  DOI: 10.1016/j.jmst.2018.04.005
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    Mg alloy AZ31B plates were processed by hot rolling with different thickness reductions per pass and pre-vertical compression followed by super-high reduction hot rolling (PVCR), respectively. Microstructure evolution, rolling formability variation and mechanical responses were investigated. As reduction per pass increased, the number of shear bands deflecting toward rolling direction increased, resulting in easy crack initiation in and around the bands. With increasing reduction per pass up to 80%, twinning and twinning-induced dynamic recrystallization (DRX) dominated the deformation of the edge material at 350 °C, resulting in local recrystallization with coarse grains and further largest edge-crack degree. Pre-induced {101ˉ2} tensile twins by pre-vertical compression (PVC) increased number density of nucleation sites for dynamic recrystallization during the subsequent severe rolling, which enhanced the dominant role of continuous dynamic recrystallization. Designed PVCR-b was proved to be a relatively effective method to improve rolling formability of rolled Mg alloy AZ31B plates. With this method, mean grain size of AZ31B plate was significantly refined from ~600 mm to ~14.1 mm and more homogeneous grain size distribution along transverse direction (TD) was achieved. In addition, basal texture intensity was greatly weakened. As a result, tensile anisotropy was distinctly decreased and fracture elongation increased dramatically.

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    Effect of applied potential on the microstructure, composition and corrosion resistance evolution of fluoride conversion film on AZ31 magnesium alloy
    Liping Wu, Changgang Wang, Durga Bhakta Pokharel, Ini-Ibehe Nabuk Etim, Lin Zhao, Junhua Dong, Wei Ke, Nan Chen
    J. Mater. Sci. Technol., 2018, 34 (11): 2084-2090.  DOI: 10.1016/j.jmst.2018.04.009
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    AZ31 magnesium (Mg) alloy was potentiostatic polarized in 0.1 M deaerated KF solution with pH 7.5 from -0.4 V to -1.4 V with an interval of -0.2 V. The polarization process was described by the potentiostatic current decay. The resultant film was analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The results demonstrated that the deposited film included a Mg(OH)2/MgF2 containing inner layer and a Mg(OH)2/MgF2/KMgF3 comprising outer layer. The high polarized potential produced high content of MgF2 but low content of KMgF3 and thin film. Conversely, the low polarized potential produced small content of MgF2 but high content of KMgF3 and thick film. The optimal corrosion resistance of the deposited film was obtained at -1.4 V, which was closely related with the content of MgF2 and KMgF3 and the film thickness.

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    Effect of heat treatment on strain-controlled fatigue behavior of cast Mg-Nd-Zn-Zr alloy
    Zhenming Li, Qigui Wang, Alan A. Luo, Jichun Dai, Hui Zou, Liming Peng
    J. Mater. Sci. Technol., 2018, 34 (11): 2091-2099.  DOI: 10.1016/j.jmst.2018.05.001
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    The influence of heat treatment on the strain-controlled fatigue behavior of cast NZ30 K alloy was investigated. Compared with the as-cast and solutionized (T4) alloys, the peak-aged (T6) and over-aged (T7) counterparts have a higher cyclic stress and a lower plastic strain value due to the precipitation strengthening. The as-cast and T4-treated alloys have a higher fatigue strength/yield strength ratio than the aged alloys, which is mainly attributed to their higher cyclic hardening. Under stress-controlled loading, the aged alloys show lower hysteresis energies than the as-cast and T4-treated counterparts, leading to longer fatigue lifetimes. For the T4-treated alloy, the cyclic hardening and fatigue failure are controlled by the dislocations-slip and twinning, while for both the as-cast and T6-treated counterparts, they are controlled by the dislocation-slip. For the T7-treated alloy, cyclic deformation and failure behavior are mainly dependent on dislocations-slip and grain boundary sliding.

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    Influence of oxygen content on the microstructure and mechanical properties of cold rolled Ti-32.5Nb-6.8Zr-2.7Sn-xO alloys after aging treatment
    Chunbo Lan, Feng Chen, Huijuan Chen, Yulong Wu, Xiangwei Wu
    J. Mater. Sci. Technol., 2018, 34 (11): 2100-2106.  DOI: 10.1016/j.jmst.2018.03.008
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    The influence of oxygen (O) content on the microstructure and mechanical properties of cold rolled Ti-32.5Nb-6.8Zr-2.7Sn-xO (TNZS-xO; x = 0, 0.3, 0.6; mass%) alloys after aging at temperature range from 350 to 600 °C for 24 h was investigated. Results showed that the cold rolled TNZS-xO alloys possess single β phase. During the aging process, O could not only effectively suppress the precipitation of ω phase but also retard the formation and decomposition of α phase. In addition, the corresponding temperatures of the maximal volume fraction of α phase precipitation and the (α+β)/β transus temperatures of the TNZS-xO alloys were all increased with the increasing of O content. For mechanical properties, it was found that the strength and Young's modulus of the TNZS-xO alloys increased owing to the ω phase and/or α phase precipitation and decreased owing to the α phase decomposition. However, the elongation showed the opposite change tendency with the above mentioned strength. The mechanical properties of TNZS-xO alloys can be controlled over a wide range by subjecting to aging treatment and/or changing their O content. When aged at or below 450 °C, the TNZS-xO alloys exhibit great potential to become a series of new candidates for biomedical applications since they possess high strength (870-1460 MPa), low Young's modulus (45.1-75.6 GPa), high strength-to-modulus ratio (0.018-0.02) and appropriate elongation (7.2%-14.9%), which are superior to those of Ti-6Al-4 V alloy and suitable for the use as bio-implant materials.

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    Fatigue crack tip plastic zone of α + β titanium alloy with Widmanstatten microstructure
    Yingjie Ma, Sabry S. Youssef, Xin Feng, Hao Wang, Sensen Huang, Jianke Qiu, Jiafeng Lei, Rui Yang
    J. Mater. Sci. Technol., 2018, 34 (11): 2107-2115.  DOI: 10.1016/j.jmst.2018.03.012
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    The recent studies had focused on the fatigue crack propagation behaviors of α + β titanium alloys with Widmanstatten microstructure. The fascinated interest of this type of microstructure is due to the superior fatigue crack propagation resistance and fracture toughness as compared to other microstructures, which was believed to be related to the fatigue crack tip plastic zone (CTPZ). In this study, the plastic deformation in fatigue CTPZ of Ti-6Al-4V titanium alloy with Widmanstatten microstructure was characterized by scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). The results showed that large-scale slipping and deformation twinning were generated in fatigue CTPZ due to the crystallographic feature of the Widmanstatten microstructure. The activation of twinning was related to the rank of Schmid factor (SF) and the diversity of twin variants developing behaviors reflected the influence of SF rank. The sizes of CTPZ under different stress intensity factors (K) were examined by the white-light coherence method, and the results revealed that the range of the plastic zone is enlarged with the increasing K (or crack length), while the plastic strain decreased rapidly with the increasing distance from the crack surface. The large-scale slipping and deformation twinning in Widmannstatten microstructure remarkably expanded the range of fatigue CTPZ, which would lead to the obvious larger size of the observed CTPZ than that of the theoretically calculated size.

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    Effect of substrate preset temperature on crystal growth and microstructure formation in laser powder deposition of single-crystal superalloy
    Zhaoyang Liu, Zi Wang
    J. Mater. Sci. Technol., 2018, 34 (11): 2116-2124.  DOI: 10.1016/j.jmst.2018.04.016
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    A successful repair of single-crystal components needs to avoid the stray grain formation and achieves continuous epitaxial growth of columnar dendrites in the repaired zone. In this study, the effect of substrate preset temperature on crystal growth and microstructure formation in laser powder deposition of single-crystal superalloy was studied through an improved mathematical model and corresponding experimental approaches. The results indicated that the variation of substrate preset temperature between -30 °C and +210 °C changes the molten pool morphology little, but obviously affects the columnar-to-equiaxed transition conditions. The preheating of substrate facilitates the stray grain formation and enlarges the primary columnar dendrite arm spacing, while the situation for precooling of substrate is opposite. Under the specific processing conditions, the critical condition for continuous epitaxial growth is that the substrate preset temperature Tsub ≤ +90 °C. When the substrate preset temperature Tsub is below +90 °C, the height ratio of melting depth to total height of the molten pool is larger than that of stray grain, ensuring that stray grains can be completely remelted and the continuous columnar dendrites during the multi-layer laser powder deposition process on (001) surface of single-crystal substrate can be achieved.

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    Fabrication of nanostructure in inner-surface of AISI 304 stainless steel pipe with surface plastic deformation
    Hongwang Zhang, Yiming Zhao, Yuhui Wang, Huaxin Yu, Chunling Zhang
    J. Mater. Sci. Technol., 2018, 34 (11): 2125-2130.  DOI: 10.1016/j.jmst.2018.05.012
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    In the present investigation, a pipe inner-surface grinding (PISG) technique was developed to fabricate nanostructure in the inner-surface of an austenitic 304 stainless steel pipe. PISG was performed by high speed shearing with hard sphere tips, leading to gradient distribution of strain, strain rate and strain gradient along depth. Nano-austenite with an average boundary spacing of 20 nm was generated, followed by deformation microstructure characterized by shear bands, multi- and uni-directional twins and planar dislocation arrays. Deformation induced grain refinement of austenitic 304 stainless steel with low stacking fault energy (SFE) covering 4-5 order’s magnitude of length scales toward nanometer regime was unified.

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    Effect of cumulative gamma irradiation on microstructure and corrosion behaviour of X65 low carbon steel
    Canshuai Liu, Jianqiu Wang, Zhiming Zhang, En-Hou Han, Wei Liu, Dong Liang, Zhongtian Yang, Xingzhong Cao
    J. Mater. Sci. Technol., 2018, 34 (11): 2131-2139.  DOI: 10.1016/j.jmst.2018.03.017
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    X65 low carbon steel was exposed to Co-60 radiation source with 1.25 MeV gamma rays, and cumulatively absorbed gamma irradiation doses (1, 2, and 3 MGy) were obtained after different exposure time (333, 667, and 1000 h). The effect of cumulative gamma irradiation on microstructure and corrosion behaviour of the carbon steel in unirradiated aerobic Beishan groundwater at 25 °C was investigated by using positron annihilation, scanning vibrating electrode, and electrochemical techniques. Cumulative gamma irradiation increases vacancy intensity and decreases open circuit potential (OCP) of carbon steel. They indicate that the irradiated carbon steel is activated. Measured current density distribution above the irradiated carbon steel shows that cumulative gamma irradiation accelerates localized corrosion after 0.5 h of immersion. In contrast, the analysis of electrochemical impedance spectroscopy of the irradiated carbon steel indicates that localized corrosion is transformed into general corrosion after 12 h of immersion, which is also accelerated by cumulative gamma irradiation.

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    Interaction between austein-ferrite phases on passive performance of 2205 duplex stainless steel
    Xuequn Cheng, Yi Wang, Xiaogang Li, Chaofang Dong
    J. Mater. Sci. Technol., 2018, 34 (11): 2140-2148.  DOI: 10.1016/j.jmst.2018.02.020
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    The passive behavior of 2205 duplex stainless steel (DSS) and its individual phases (α-phase, γ-phase) in neutral 3.5% NaCl solution was investigated by various electrochemical methods. The results indicated that galvanic effect between α and γ phases cannot deteriorate local corrosion, but favors the enhancement of the passive film. Under the galvanic effect, the diffusion of the dissolved passive cations would be promoted in a short distance between α and γ zones, leading to modifications of the chemical composition and semiconductive property of the passive film and therefore the enhancement of the corrosion resistance of DSS 2205.

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    Dissolution and repair of passive film on Cu-bearing 304L stainless steels immersed in H2SO4 solution
    Xinrui Zhang, Jinlong Zhao, Tong Xi, M. Babar Shahzad, Chunguang Yang, Ke Yang
    J. Mater. Sci. Technol., 2018, 34 (11): 2149-2159.  DOI: 10.1016/j.jmst.2018.02.017
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    The antibacterial Cu-bearing 304L stainless steel is a new kind of structural and functional integrated metal material. In this work, evolution behavior of passive film of different heat treated Cu-bearing 304L stainless steel immersed in 0.5 M H2SO4 solution was investigated by using electrochemical measurements, atomic force microscopy (AFM) observation and X-ray photoelectron spectroscopy (XPS) analysis. The results show that the solution and aging treated samples have the similar polarization behaviors. The passive film impedance experiences an initial decrease within 7 days followed by a subsequent increase, while the defect density of passive film presents the opposite trend. Meanwhile, the evolution of surface morphology and the estimated thickness of the passive film confirm that it experiences initial dissolution and follow-up repair. Furthermore, the Cr3+ content in passive film undergoes sequential reduction to increase, however the variation tendency of Cu2+ content is just opposite, indicating that the content variation of Cr and Cu in passive film reflects the competitive process of film dissolution and repair. In addition, compared with solution treated samples, aged samples have a bigger icorr value and the rougher passive film. This indicates that the passive film of solution treated steel is more compact and stable.

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    Evolution of interface character distribution in duplex stainless steel processed by cross-rolling and annealing
    Ming Wang, Ting Xu, Yanli Zhu, Wenhong Yin, Hong Guo, Ertuan Zhao, Xiaoying Fang, Weiguo Wang
    J. Mater. Sci. Technol., 2018, 34 (11): 2160-2166.  DOI: 10.1016/j.jmst.2018.02.018
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    Duplex stainless steel UNS S31803 samples were cross-rolled with a true strain of ε = 2 followed by annealing at 1323 K for 2 min and 240 min, respectively. The distributions of intervariant boundary planes in the precipitated austenite (A) from ferrite (F) and phase boundary planes conforming to Kurdjumov-Sache (K-S) orientation relationship (OR) were characterized by electron backscatter diffraction (EBSD) and the five-parameter analysis (FPA) method, respectively. The intervariant boundary planes with misorientation angle of 60° around <111> and <011> occur frequently and tend to terminate on the {111} plane. At the grain size level of 4 μm, the phase boundary appears to be connected with the K-S OR terminating on {110}F‖{111}A at the early stage of annealing. When the grain size reaches approximately 20 μm, phase boundary was modified into {541}F‖{533}A due to twinning in austenite during annealing.

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    Optimization of cold-sprayed AA2024/Al2O3 metal matrix composites via friction stir processing: Effect of rotation speeds
    Kang Yang, Wenya Li, Chunjie Huang, Xiawei Yang, Yaxin Xu
    J. Mater. Sci. Technol., 2018, 34 (11): 2167-2177.  DOI: 10.1016/j.jmst.2018.03.016
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    In this study, friction stir processing (FSP) was employed to modify cold-sprayed (CSed) AA2024/Al2O3 metal matrix composites (MMCs). Three different rotation speeds with a constant traverse speed were used for FSP. Microstructural analysis of the FSPed specimens reveals significant Al2O3 particle refinement and improved particle distribution over the as-sprayed deposits. After FSP, a microstructural and mechanical gradient MMC through the thickness direction was obtained. Therefore, a hybrid technique combining these two solid-state processes, i.e. CS and FSP, was proposed to produce functionally gradient deposits. The Guinier-Preston-Bagaryatskii zone was dissolved during FSP, while the amounts at different rotation speeds were approximately the same, which is possibly due to the excellent thermal conductivity of the used Cu substrate. Mechanical property tests confirm that FSP can effectively improve the tensile performance and Vickers hardness of CSed AA2024/Al2O3 MMCs. The properties can be further enhanced with a larger rotation speed with a maximum increase of 25.9% in ultimate tensile strength and 27.4% in elongation at 1500 rpm. Friction tests show that FSP decreases the wear resistance of CSed MMCs deposits due to the breakup of Al2O3 particles. The average values and fluctuations of friction coefficients at different rotation speeds vary significantly.

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    Inhomogeneous deformation of {111} grain in cold rolled tantalum
    Yahui Liu, Shifeng Liu, Chao Deng, Haiyang Fan, Xiaoli Yuan, Qing Liu
    J. Mater. Sci. Technol., 2018, 34 (11): 2178-2182.  DOI: 10.1016/j.jmst.2018.03.015
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    The microstructures of {111} grain were characterized in detailed and systematically investigated with the aid of electron backscatter diffraction (EBSD) and transmission electron microscope (TEM). The stored energy in different regions in the grain was evaluated by the band contrast values collected from EBSD. The results show that the distribution of energy is inhomogeneous through the grain. Especially, the regions containing the least and the largest energy were extracted from the EBSD data, and then quantitatively analyzed based on the misorientation and Schmid factor. Many peaks with large misorientation appeared in the region containing larger energy, and these peaks represent the existences of micro-bands and micro-shear bands in {111} grain. The results of Schmid factor suggest that the region containing larger energy is prone to deforming ahead of the region with less stored energy, implying the more serious subdivision of the microstructure of region with larger stored energy.

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    Achieving ultra-high strength friction stir welded joints of high nitrogen stainless steel by forced water cooling
    H. Zhang, D. Wang, P. Xue, L.H. Wu, D.R. Ni, B.L. Xiao, Z.Y. Ma
    J. Mater. Sci. Technol., 2018, 34 (11): 2183-2188.  DOI: 10.1016/j.jmst.2018.03.014
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    The microstructure and properties of water-cooled and air-cooled friction stir welded (FSW) ultra-high strength high nitrogen stainless steel joints were comparatively studied. With additional rapid cooling by flowing water, the peak temperature and duration at elevated temperature during FSW were significantly reduced. Compared to those in the air-cooled joint, nugget zone with finer grains (900 nm) and heat affected zone with higher dislocation density were successfully obtained in the water-cooled joint, leading to significantly improved mechanical properties. The wear of the welding tool was significantly reduced with water cooling, resulting in better corrosion resistance during the immersion corrosion test.

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    Synthesis of porous carbon spheres derived from lignin through a facile method for high performance supercapacitors
    Yuemei Chen, Guoxiong Zhang, Jingyuan Zhang, Haibo Guo, Xin Feng, Yigang Chen,
    J. Mater. Sci. Technol., 2018, 34 (11): 2189-2196.  DOI: 10.1016/j.jmst.2018.03.010
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    Porous carbon spheres (PCS) derived from lignin have been prepared through a facile method and fabricated as electrodes for electric double-layer capacitors. Spherical shaped mixtures of lignosulfonate and crystalized KOH are formed by spray drying of a solution of lignosulfonate and KOH. Activation by KOH is performed at high temperatures along with lignosulfonate carbonization. With an appropriate pore structure, the obtained PCS have a specific surface area of 1372.87 m2 g-1 and show a capacitance of 340 F g-1 in 3 M KOH at a current density of 0.5 A g-1. Moreover, a symmetric supercapacitor fabricated using the PCS as electrodes show a maximum capacitance of 68.5 F g-1, and an energy density of 9.7 W h kg-1 at a power density of 250 W kg-1. The capacity retention is more than 94.5% after 5000 galvanostatic charge-discharge cycles. The excellent characteristics seem to be ascribed to the pore structures of PCS that have a large specific surface area and a low electrical resistance.

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    Enhanced efficiency of graphene-silicon Schottky junction solar cell through inverted pyramid arrays texturation
    Jiajia Qiu, Yudong Shang, Xiuhua Chen, Shaoyuan Li, Wenhui Ma, Xiaohan Wan, Jia Yang, Yun Lei, Zhengjie Chen
    J. Mater. Sci. Technol., 2018, 34 (11): 2197-2204.  DOI: 10.1016/j.jmst.2018.04.008
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    Nanostructures of silicon are gradually becoming hot candidate due to outstanding capability for trapping light and improving conversion efficiency of solar cell. In this paper, silicon nanowires (SiNWs) and silicon inverted pyramid arrays (SiIPs) were introduced on surface of Gr-Si solar cell through silver and copper-catalyzed chemical etching, respectively. The effects of SiNWs and SiIPs on carrier lifetime, optical properties and efficiency of Gr-SiNWs and Gr-SiIPs solar cells were systematically analyzed. The results show that the inverted pyramid arrays have more excellent ability for balancing antireflectance loss and surface area enlargement. The power conversion efficiency (PCE) and carrier lifetime of Gr-SiIPs devices respectively increase by 62% and 34% by comparing with that of Gr-SiNWs solar cells. Finally, the Gr-SiIPs cell with PCE of 5.63% was successfully achieved through nitric acid doping. This work proposes a new strategy to introduce the inverted pyramid arrays for improving the performance of Gr-Si solar cells.

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    Reinforcing epoxy resin with nitrogen doped carbon nanotube: A potential lightweight structure material
    Qi Wang, Guodong Wen, Junnan Chen, Dang Sheng Su
    J. Mater. Sci. Technol., 2018, 34 (11): 2205-2211.  DOI: 10.1016/j.jmst.2018.02.021
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    The outstanding mechanical properties of nanocarbon materials, especially carbon nanotube (CNT), make them one of the most promising reinforcing nanofillers for the high-performance lightweight structural material. However, the complicated but not eco-friendly surface functionalization processes (e.g. HNO3 oxidation) are generally necessary to help disperse nanocarbon materials into epoxy or build chemical bonds between them. Herein, nitrogen doped carbon nanotube (NCNT) was used to replace CNT to reinforce the epoxy resin, and the mechanical properties of the NCNT/epoxy nanocomposite showed significant superiorities over the CNT/epoxy nanocomposites. The fabrication process was simple and environmentally friendly, and avoided complicated, polluting and energy intensive surface functionalization processes. Moreover, the NCNT/epoxy suspension exhibited a relative low viscosity, which was favorable for the subsequent application. The reinforcing mechanism of NCNT was also proposed. The present work gives out an easy solution to the preparation of a high-performance nanocomposite as a potential lightweight structure material.

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    Oxidation behaviors of Co-Al-W-0.1B superalloys in a long-term isothermal exposure at 900 °C
    Yuzhi Li, Florian Pyczak, Jonathan Paul, Zekun Yao
    J. Mater. Sci. Technol., 2018, 34 (11): 2212-2217.  DOI: 10.1016/j.jmst.2018.03.013
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    Co-Al-W-0.1B superalloys have been isothermally oxidized at 900 °C for 1000, 5000 and 10000 h in order to investigate their oxidation behaviors. The oxide layers and morphologies were characterized by X-ray diffraction and scanning electron microscopy combined with energy-dispersive spectroscopy. After 1000 h exposure, a Co3W/γ zone, an Al2O3 layer, a mixture of Co, Al, W oxides layer and a CoO layer are established on the substrate alloys. After extended oxidation, a discontinuous Al2O3 layer in Co-9Al-8W-0.1B and Co-9Al-9W-0.1B alloys leads to an additional mixed oxide layer on the substrate instead of the Co3W/γ zone. The oxide layers that form on the Co-9Al-8W-0.1B and Co-9Al-9W-0.1B alloys are much thicker than those on the Co-9Al-11W-0.1B alloy, and continuously thicken during oxidation. The higher content of W is beneficial to improving the oxidation resistance as it facilitates a faster formation of Co3W as well as Al2O3.

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    Preparation and characterization of organic pigments and their fluorescence properties depending on bulk structure
    Jie Du, Rong Yang, Changqing Fang, Xing Zhou, Shaofei Pan, Wanqing Lei, Jian Su, Youliang Cheng, Donghong Liu
    J. Mater. Sci. Technol., 2018, 34 (11): 2218-2224.  DOI: 10.1016/j.jmst.2018.05.017
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    Fluorescent pigments, based on the optical or electrooptical properties of dyes, are the main component in fluorescent coatings and inks. In this study, three kinds of dyes (Rhodamine B, Light Green SF Yellowish, Coumarin) with four different ratios (2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%) were employed as luminophor, and the melamine-formaldehyde (MF) resin was used as curing resin to prepare fluorescent pigments in different color. Fourier transform infrared spectroscopy and X-ray diffractometry were carried out to analyze the structure of the fluorescent pigments. Scanning electron microscopy and particle size distribution were used to present the morphology of fluorescent pigments. UV-vis and fluorescence spectrum were used to demonstrate the optical properties. It can be concluded that, coumarin pigments possessed consecutive structure in MF resin while rhodamine B might be the best for the preparation of printing inks among the three kinds of dyes from the view of particle size. The TG results presented that all the pigments showed good thermal stability, which might possess potential application in high speed printing industry.

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