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 March 2019, Volume 35 Issue 3 Previous Issue    Next Issue
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    Orginal Article
    Understanding of degradation-resistant behavior of nanostructured thermal barrier coatings with bimodal structure
    Guangrong Li, Guanjun Yang
    J. Mater. Sci. Technol., 2019, 35 (3): 231-238.  DOI: 10.1016/j.jmst.2018.09.054
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    Nanostructured thermal barrier coatings (TBCs) often provide high degradation resistance, as well as extended lifetime. However, the underlying mechanism has not been fully understood. In this study, the sintering characteristics of nanostructured yttria-stabilized zirconia (YSZ) coatings were investigated, and compared with those of the conventional YSZ coatings. Multiscale characterizations of the changes in microstructures and properties were performed. Results showed that the enhanced high-performance durability was mainly attributed to different sintering mechanisms of lamellar zones and nanozones. Sintering characteristics of the lamellar zones were similar to those of the conventional coatings. Stage-sensitive healing of two-dimensional (2D) pores dominated the sintering behavior of the lamellar zones. However, the differential densification rates between nanozones and lamellar zones of the nanostructured TBCs led to the formation of coarse voids. This counteractive effect, against healing of 2D pores, was the main factor contributing to the retardation of the performance degradation of bimodal TBCs during thermal exposure. Based on the understanding of the performance-degradation resistance, an outlook towards TBCs with higher performances was presented.

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    The 3-dimensional morphology of dendrite during equiaxed solidification of an Al-5 wt.% Cu alloy
    Xiaoping Ma, Dianzhong Li
    J. Mater. Sci. Technol., 2019, 35 (3): 239-247.  DOI: 10.1016/j.jmst.2018.09.042
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    In a sample quenched during equiaxed solidification of an Al-5?wt.% Cu alloy, the multi-scales 3-dimensional morphology of equiaxed dendrite was observed. The slim primary stem and secondary branches constitute the frame of dendrite, and rows of dense tertiary branches further divide the 3-dimensional space. In the divided space, the quartic branches grow further. The dendritic branches, which are perpendicular to each other, can change their growth directions and coalesce into a whole. In the tertiary branches and quartic branches, the formation of double branch structures is induced by competitive growth. The branch that wins in the competitive growth will produce a cabbage-like structure by wrapping the failed branches. In addition, the side branch can also wrap the original parent branch to produce cabbage-like structures. Depending on the historical growth direction, the dendritic arms can form vein-like and spicate structures, and the shapes of single dendritic arm may be the cylinder, plate and trapezoid platform. According to the compositions and etching morphology, the single dendritic arm in the final solidification structures should coalesce from a fine porous structure. The porous structures at different length-scales are principally induced by the preferential growth. Based on 3-dimensional morphology of equiaxed dendrite, a new research object for the investigation of microsegregation was suggested.

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    Microdomain atomic structure of Zr50Pd40Al10 metallic glasses and its formation mechanism
    Kai Li, Fangliang Gao, Yu-Jen Chou, Kaixiang Shen, Guoqiang Li
    J. Mater. Sci. Technol., 2019, 35 (3): 248-253.  DOI: 10.1016/j.jmst.2018.09.044
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    Zr-based Zr50Pd40Al10 metallic glasses has not only crystalline phases of about 5?nm in diameter but also amorphous phases. In this work, the radial distribution functions (RDFs) of amorphous structure of Zr50Pd40Al10 metallic glasses were firstly measured by electron diffraction, and then Reverse Monte Carlo (RMC) optimization accompanied by density functional theory (DFT) calculations. The amorphous structure has not only short-range order but also good medium-range order. In the RDFs of its amorphous structure, the first and the second peaks are located at 2.96?? and 4.79??, respectively. Partial radical distribution functions (PRDFs) show that the contributions of the first and the second nearest-neighbor distances of various atom pairs to the G(r) peak values, and the first nearest-neighbor distances of Pd-Zr and Zr-Zr atom pairs are the sources of main G(r) peak values between 2?? and 6??. The competition mechanism for generating the Pd25Zr55Al20 amorphous phase and the intermetallic crystalline phase Pd11Zr9 is associated with the differences of atomic radius, the proportion, and the melting point of different atoms, as well as the heat of mixing between atoms, leading to an equilibrium state of the two phases. Accordingly, a composite system with intertwined nanocrystals and amorphous phases is in turn formed, and improves the stability of the material.

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    In vitro corrosion resistance and antibacterial performance of novel tin dioxide-doped calcium phosphate coating on degradable Mg-1Li-1Ca alloy
    Lan-Yue Cui, Guang-Bin Wei, Zhuang-Zhuang Han, Rong-Chang Zeng, Lei Wang, Yu-Hong Zou, Shuo-Qi Li, Dao-Kui Xu, Shao-Kang Guan
    J. Mater. Sci. Technol., 2019, 35 (3): 254-265.  DOI: 10.1016/j.jmst.2018.09.052
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    A SnO2-doped calcium phosphate (Ca-P-Sn) coating was constructed on Mg-1Li-1Ca alloy by a hydrothermal process. The fabricated functional coatings were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). A triple-layered structure, which is composed of Ca3(PO4)2, (Ca, Mg)3(PO4)2, SnO2, and MgHPO4·3H2O, is evident and leads to the formation of Ca10(PO4)6(OH)2 in Hank’s solution. Electrochemical measurements, hydrogen evolution tests and plating counts reveal that the corrosion resistance and antibacterial activity were improved through the coating treatment. The embedded SnO2 nanoparticles enhanced crystallisation of the coating. The formation and degradation mechanisms of the coating were discussed.

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    Designing a high Si reduced activation ferritic/martensitic steel for nuclear power generation by using Calphad method
    Chao Liu, Quanqiang Shi, Wei Yan, Chunguang Shen, Ke Yang, Yiyin Shan, Mingchun Zhao
    J. Mater. Sci. Technol., 2019, 35 (3): 266-274.  DOI: 10.1016/j.jmst.2018.07.002
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    A high Si reduced activation ferritic/martensitic (RAFM) steel for nuclear structure application is successfully designed by using Calphad method. The main designed chemical composition is C 0.18-0.22%, Cr 10.0-10.5%, W 1.0-1.5%, Si 1.0-1.3%, V+Ta 0.30-0.45%, and Fe in balance. High Si design brings excellent corrosion resistance, while low activation is advantageous in the nuclear waste processing. The experimental results indicate that the newly designed high Si RAFM steel had full martensitic structure and uniformly distributed fine second phase particles, and exhibited excellent mechanical properties and corrosion resistance. Compared to the P91 steel, this new RAFM steel designed by Calphad method is expected to be a promising candidate used in nuclear power generation, which also provides a new and effective approach to the development of RAFM steel for nuclear application.

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    Research Article
    Self-lubricate and anisotropic wear behavior of AZ91D magnesium alloy reinforced with ternary Ti2AlC MAX phases
    Wenbo Yu, Deqiang Chen, Liang Tian, Hongbin Zhao, Xiaojun Wang
    J. Mater. Sci. Technol., 2019, 35 (3): 275-284.  DOI: 10.1016/j.jmst.2018.07.003
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    The dry sliding wear behavior of Ti2AlC reinforced AZ91 magnesium composites was investigated at sliding velocity of 0.5 m/s under loads of 10, 20, 40 and 80 N using pin-on-disk configuration against a Cr15 steel disc. Wear rates and friction coefficients were registered during wear tests. Worn tracks and wear debris were examined by scanning electron microscopy, energy dispersive X-ray spectrometry and transmission electron microscopy in order to obtain the wear mechanisms of the studied materials. The main mechanisms were characterized as the magnesium matrix oxidation and self-lubrication of Ti2AlC MAX phase. In all conditions, the composites exhibit superior wear resistance and self-lubricated ability than the AZ91 Mg alloy. In addition, the anisotropic mechanisms in tribological properties of textured Ti2AlC-Mg composites were confirmed and discussed.

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    Sepiolite/Cu2O/Cu photocatalyst: Preparation and high performance for degradation of organic dye
    Peisan Wang, Chunxia Qi, Luyuan Hao, Pengchao Wen, Xin Xu
    J. Mater. Sci. Technol., 2019, 35 (3): 285-291.  DOI: 10.1016/j.jmst.2018.03.023
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    A novel ternary sepiolite/Cu2O/Cu (SCC) nanocomposite was successfully synthesized by a facile one-pot method. The Cu2O/Cu nanoparticles in the SCC nanocomposite are well dispersed on the sepiolite surface. It exhibited enhanced photocatalytic performance in the degradation of congo red (CR), remarkably superior to that of Cu2O or Cu2O/Cu nanoparticles. Elemental copper in the SCC serves as a good electron acceptor to promote the transfer of photo-generated electrons in Cu2O and suppress the recombination of the photo-generated electrons and holes of the composite. The enhanced photocatalytic efficiency is attributed to the synergistic effect of sepiolite and Cu2O/Cu. This type of SCC nanocomposites is a promising candidate as photocatalytic material for environmental protection.

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    High-quality liquid phase-pulsed laser ablation graphene synthesis by flexible graphite exfoliation
    M. Jalili, H. Ghanbari, S.Moemen Bellah, R. Malekfar
    J. Mater. Sci. Technol., 2019, 35 (3): 292-299.  DOI: 10.1016/j.jmst.2018.09.048
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    This work reports a one-pot procedure of laser ablation on a graphite target in a liquid medium, based on the variation of different parameters such as target type, laser wavelength, and ablation medium, to obtain high-quality graphene nanosheets. The morphology of derived products was characterized by the field emission scanning electron microscopy (FE-SEM). Then, the morphology and structure of the optimized sample were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet-visible-near infrared (UV-vis-NIR) spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). By controlling the laser ablation parameters, we were able to prepare micrometer-sized few-layer graphene nanosheets with mainly less than ten layers. Such synthesized graphene nanosheets were grown at the surface of a flexible graphite target, indicating many potential applications in fundamental research, electrochemical and as hydrophobic surfaces.

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    High He-ion irradiation resistance of CrMnFeCoNi high-entropy alloy revealed by comparison study with Ni and 304SS
    Lixin Yang, Hualong Ge, Jian Zhang, Ting Xiong, Qianqian Jin, Yangtao Zhou, Xiaohong Shao, Bo Zhang, Zhengwang Zhu, Shijian Zheng, Xiuliang Ma
    J. Mater. Sci. Technol., 2019, 35 (3): 300-305.  DOI: 10.1016/j.jmst.2018.09.050
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    High entropy alloys (HEAs) have presented potential applications in nuclear power plants owing to their novel atomic structure based high irradiation resistance. However, understanding of He-ion irradiation of HEAs is still lacking. In this work, we reveal He-ion irradiation resistance of HEA CrMnFeCoNi by comparison study with a pure Ni and a 304 stainless steel (304SS). It is found that the damage structure in the three materials can be characterized with He bubbles and stacking faults/stacking fault tetrahedrons ((SFs/SFTs), which show a similar depth distribution after He-ion irradiation at both RT and 450?°C. Although the He bubbles have a similar size about 2?nm after irradiation at RT, the He bubble sizes of the HEA, 304SS, and Ni increase to 4.0?±?0.9, 5.3?±?1.0 and 6.7?±?1.0?nm after irradiation at 450?°C, respectively. Moreover, the density of SFs/SFTs displays in an order of Ni < 304SS?

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    A novel heat-resistant Al-Si-Cu-Ni-Mg base material synergistically strengthened by Ni-rich intermetallics and nano-AlNp microskeletons
    Kaiqi Hu, Qingfei Xu, Xia Ma, Qianqian Sun, Tong Gao, Xiangfa Liu
    J. Mater. Sci. Technol., 2019, 35 (3): 306-312.  DOI: 10.1016/j.jmst.2018.09.051
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    In this work, nano-AlN particle (nano-AlNp) microskeletons were introduced into an Al-Si-Cu-Ni-Mg alloy by Al-8AlN master alloy in which the nano-AlNp reinforcements connect with each other to form three-dimensional networks. It is found that these nano-AlNp microskeletons mainly distribute in the binary Al-Si eutectic zones resulting in flaky eutectic Si phases being modified to particulates. Meanwhile, the microskeletons strengthen the matrix synergistically with semi-continuous Ni-rich intermetallics in three dimensions. The tensile mechanical properties, micro-hardness and thermal expansion properties of the alloy at different temperatures are significantly improved. Especially, the ultimate tensile strength (UTS) at 350?°C increases from 85?MPa to 106?MPa, rising by 24.7%, which is ascribed to nano-AlNp microskeletons assisting intermetallics with undertaking mechanical loading, and to the modification of eutectic Si phases to reduce the stress concentration at elevated temperatures.

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    Y5Si3C and Y3Si2C2: Theoretically predicted MAX phase like damage tolerant ceramics and promising interphase materials for SiCf/SiC composites
    Yanchun Zhou, Huimin Xiang, Fu-Zhi Dai
    J. Mater. Sci. Technol., 2019, 35 (3): 313-322.  DOI: 10.1016/j.jmst.2018.09.041
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    Researching for interphase materials that can protect SiC fibers from oxygen and water vapor attacks has become one of the most important issues for the applications of SiCf/SiC composites in high-temperature combustion environment. However, such kinds of interphase materials are not available yet. Herein, we report theoretically predicted properties of two promising interphase materials Y5Si3C and Y3Si2C2. Although crystallizing in different structures, they share the common features of layered structure, anisotropic chemical bonding, anisotropic electrical and mechanical properties, and low shear deformation resistance. The bulk moduli for Y5Si3C and Y3Si2C2 are 78 and 93?GPa, respectively; while their shear moduli are 52 and 50?GPa, respectively. The maximum to minimum Young’s modulus ratios are 1.44 for Y5Si3C and 3.27 for Y3Si2C2. Based on the low shear deformation resistance and low Pugh's ratios (G/B?=?0.666 for Y5Si3C and 0.537 for Y3Si2C2; G: shear modulus; B: bulk modulus), they are predicted as damage tolerant and soft ceramics with predicted Vickers hardness of 9.6 and 6.9?GPa, respectively. The cleavage plane and possible slip systems are (000l) and (0001)[112ˉ0] and (101ˉ0)[0001] for Y5Si3C, and those for Y3Si2C2 are {h00} and (010)[101]. Since the oxidation products are water-vapor resistant Y2Si2O7, Y2SiO5 and/or Y2O3 upon oxidation, and the volume expansions are ca 140% and ca 26% for Y5Si3C and Y3Si2C2, they are expected to seal the interfacial cracks in SiCf/SiC composites. The unique combination of easy cleavage, low shear deformation resistance, volume expansions upon oxidation, and the resistance of the oxidation products to water vapor attack warrant them promising as interphase materials of SiCf/SiC composites for water-vapor laden environment applications.

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    A facile synthesis of supported amorphous iron oxide with high performance for Cr(VI) removal from aqueous solution under visible light irradiation
    Xianliang Hou, Zhen Wang, Changqing Fang, Youliang Cheng, Tiehu Li
    J. Mater. Sci. Technol., 2019, 35 (3): 323-329.  DOI: 10.1016/j.jmst.2018.09.061
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    A series of supported iron oxide nanoparticles were prepared by impregnation with Fe(NO3)3 supported on TiO2, followed by low-temperature calcination. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra and BET have been used to characterize the samples. These iron oxide-impregnated TiO2 were examined for photocatalytic reduction of Cr(VI). The experiments demonstrated that Cr(VI) in aqueous solution was more efficiently reduced using Fe2O3/TiO2 heterogeneous photocatalysts than either pure Fe2O3 or TiO2 under visible light irradiation. All TiO2 supported samples were somewhat active for visible light photoreduction. With an optimal mole ratio of 0.05-Fe/Ti, the highest rate of Cr(VI) reduction was achieved under the experimental conditions. We also compared the photoreactivity of TiO2 supported iron oxide samples with that supported on Al2O3 and ZrO2. It can be noted that iron oxide nanoparticles deposited on high surface area supports to increase the solid-liquid contact area renders it considerably more active. Noticeably, iron oxide cluster size and dispersion are important parameters in synthesizing active, supported Iron oxide nanoparticles. In addition, the interaction between iron oxide and TiO2 was proposed as the source of photoactivity for Cr(VI) reduction.

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    Improvement on the interface properties of p-GaAs/n-InP heterojunction for wafer bonded four-junction solar cells
    Mengyan Zhang, Tao Ning, Jie Chen, Lijie Sun, Lihua Zhou
    J. Mater. Sci. Technol., 2019, 35 (3): 330-333.  DOI: 10.1016/j.jmst.2018.09.064
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    The p-GaAs/n-InP heterojunction was fabricated by direct wafer bonding technology. The optimized atomic level contact between GaAs and InP is critical for getting good ohmic contact and removing the bubbles or voids at the interface, which is helpful to enhance the efficiency of wafer bonded multi-junction solar cells. Through the surface megasonic cleaning and the plasma treatment, we have achieved the high quality bonding interface without bubbles or voids and with interface resistivity of about 0.1 ohms/cm2. A GaInP/GaAs//InGaAsP/InGaAs 4-junction solar cell was prepared with the high efficiency of 34.4% (AM0) at 1 sun.

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    Fatigue behavior of CoCrFeMnNi high-entropy alloy under fully reversed cyclic deformation
    Y.Z. Tian, S.J. Sun, H.R. Lin, Z.F. Zhang
    J. Mater. Sci. Technol., 2019, 35 (3): 334-340.  DOI: 10.1016/j.jmst.2018.09.068
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    Bulk ultrafine-grained (UFG) CoCrFeMnNi high-entropy alloy (HEA) with fully recrystallized microstructure was processed by cold rolling and annealing treatment. The high-cycle fatigue behaviors of the UFG HEA and a coarse-grained (CG) counterpart were investigated under fully reversed cyclic deformation. The fatigue strength of the UFG HEA can be significantly enhanced by refining the grain size. However, no grain coarsening was observed in the UFG HEA during fatigue tests. Mechanisms for the superior mechanical properties of the UFG HEA were explored.

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    Modification of NiCoCrAlY with Pt: Part I. Effect of Pt depositing location and cyclic oxidation performance
    Yingfei Yang, Hongrui Yao, Zebin Bao, Pan Ren, Wei Li
    J. Mater. Sci. Technol., 2019, 35 (3): 341-349.  DOI: 10.1016/j.jmst.2018.09.039
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    Pt layers of 5?μm in thickness were electroplated before or after depositing NiCoCrAlY coating by arc ion plating (AIP) aiming for identifying the effect of Pt enriching position on microstructure and cyclic oxidation behavior of Pt modified NiCoCrAlY coatings. Al-rich zones formed at the same position of Pt-rich zones for both modified coatings due to uphill diffusion of Al driven by Pt. Cyclic oxidation tests at 1000 and 1100?°C indicated that oxidation resistance of NiCoCrAlY was improved by Pt modification via different mechanisms: at surface, Pt-rich zone promoted selective oxidation of Al to form α-Al2O3, whilst at coating/substrate interface Pt-rich zone acted as effective diffusion barrier for titanium. Roles of Pt played in enhancing the oxidation performance of various Pt-modified NiCoCrAlY coating were investigated.

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    Modification of NiCoCrAlY with Pt: Part II. Application in TBC with pure metastable tetragonal (t′) phase YSZ and thermal cycling behavior
    Chuntang Yu, He Liu, Chengyang Jiang, Zebin Bao, Shenglong Zhu, Fuhui Wang
    J. Mater. Sci. Technol., 2019, 35 (3): 350-359.  DOI: 10.1016/j.jmst.2018.09.040
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    A thermal barrier coating system comprising Pt-modified NiCoCrAlY bond coating and nanostructured 4?mol.% yttria stabilized zirconia (4YSZ, hereafter) top coat was fabricated on a second generation Ni-base superalloy. Thermal cycling behavior of NiCoCrAlY-4YSZ thermal barrier coatings (TBCs) with and without Pt modification was evaluated in ambient air at 1100?°C up to 1000 cycles, aiming to investigate the effect of Pt on formation of thermally grown oxide (TGO) and oxidation resistance. Results indicated that a dual layered TGO, which consisted of top (Ni,Co)(Cr,Al)2O4 spinel and underlying α-Al2O3, was formed at the NiCoCrAlY/4YSZ interface with thickness of 8.4?μm, accompanying with visible cracks at the interface. In contrast, a single-layer and adherent α-Al2O3 scale with thickness of 5.6?μm was formed at the interface of Pt-modified NiCoCrAlY and 4YSZ top coating. The modification of Pt on NiCoCrAlY favored the exclusive formation of α-Al2O3 and the reduction of TGO growth rate, and thus could effectively improve overall oxidation performance and extend service life of TBCs. Oxidation and degradation mechanisms of the TBCs with/without Pt-modification were discussed.

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    Non-destructive microstructural analysis by electrical conductivity: Comparison with hardness measurements in different materials
    Gonçalo L. Sorger, J.P. Oliveira, Patrick L. Inácio, Norbert Enzinger, Pedro Vilaça, R.M. Miranda, Telmo G. Santos
    J. Mater. Sci. Technol., 2019, 35 (3): 360-368.  DOI: 10.1016/j.jmst.2018.09.047
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    The use of non-destructive evaluation (NDE) techniques for assessing microstructural changes in processed materials is of particular importance as it can be used to assess, qualitatively, the integrity of any material/structure. Among the several NDE techniques available, electrical conductivity measurements using eddy currents attract great attention owing to its simplicity and reliability. In this work, the electrical conductivity profiles of friction stir processed Ti6Al4V, Cu, Pb, S355 steel and gas tungsten arc welded AISI 304 stainless steel were determined through eddy currents and four-point probe. In parallel, hardness measurements were also performed. The profiles matched well with the optical macrographs of the materials: while entering in the processed region a variation in both profiles was always observed. One particular advantage of electrical conductivity profiles over hardness was evident: it provides a better resolution of the microstructural alterations in the processed materials. Moreover, when thermomechanical processing induces microstructural changes that modify the magnetic properties of a material, eddy currents testing can be used to qualitatively determine the phase fraction in a given region of the material. A qualitative relation between electrical conductivity measurements and hardness is observed.

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    A promising new class of irradiation tolerant materials: Ti2ZrHfV0.5Mo0.2 high-entropy alloy
    Yiping Lu, Hefei Huang, Xuzhou Gao, Cuilan Ren, Jie Gao, Huanzhi Zhang, Shijian Zheng, Qianqian Jin, Yonghao Zhao, Chenyang Lu, Tongmin Wang, Tingju Li
    J. Mater. Sci. Technol., 2019, 35 (3): 369-373.  DOI: 10.1016/j.jmst.2018.09.034
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    Recently, high-entropy alloys (HEAs) or multi-principal-element alloys with unprecedented physical, chemical, and mechanical properties, have been considered as candidate materials used in advanced reactors due to their promising irradiation resistant behavior. Here, we report a new single-phase body-centered cubic (BCC) structured Ti2ZrHfV0.5Mo0.2 HEA possessing excellent irradiation resistance, i.e., scarcely irradiation hardening and abnormal lattice constant reduction after helium-ion irradiation, which is completely different from conventional alloys. This is the first time to report the abnormal XRD phenomenon of metallic alloys and almost no hardening after irradiation. These excellent properties make it to be a potential candidate material used as core components in next-generation nuclear reactors. The particular irradiation tolerance derives from high density lattice vacancies/defects.

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    Enhanced age-hardening behavior in Al-Cu alloys induced by in-situ synthesized TiC nanoparticles
    Huabing Yang, Tong Gao, Huaning Zhang, Jinfeng Nie, Xiangfa Liu
    J. Mater. Sci. Technol., 2019, 35 (3): 374-382.  DOI: 10.1016/j.jmst.2018.09.029
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    The influence of in-situ synthesized TiC nanoparticles on age-hardening behavior of Al-Cu alloys was investigated in Al-4.5Cu-1.5TiC alloy. It was found that TiC nanoparticles decrease the peak-age time effectively, from about 20?h for Al-4.5Cu alloy decreasing to about 12?h for the Al-4.5Cu-1.5TiC. Mechanical property test shows that the age-hardening effect has been improved by the TiC nanoparticles. The increment of yield strength before and after aging is about 84?MPa for Al-4.5Cu, while, it reaches to about 113?MPa for the Al-4.5Cu-1.5TiC. After aging heat treatment, precipitates have been observed both in matrix and around TiC nanoparticles. Due to the difference of coefficient of thermal expansion between TiC and Al, high density dislocations in the Al-4.5Cu-1.5TiC were generated during water quenching after solution. Dislocations play a role of diffusion path for Cu atoms during aging, which reduces the peak-age time. Alpha-Al lattice distortion resulted from lattice mismatch of TiC/Al interface induces the precipitation of θ? phase around TiC nanoparticles, which increases the number density of θ? and improves the age-hardening effect. This finding is supposed to be also applicable to alloy systems of Al-Cu-Mg, Al-Cu-Mg-Li, Al-Cu-Mg-Ag, etc.

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    Enhancing both strength and toughness of carbon/carbon composites by heat-treated interface modification
    Jiajia Sun, Hejun Li, Liyuan Han, Qiang Song
    J. Mater. Sci. Technol., 2019, 35 (3): 383-393.  DOI: 10.1016/j.jmst.2018.09.055
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    A simple method to increase both strength and toughness of carbon/carbon (C/C) composites is presented. This method is based on the heat treatment of the pre-deposited thin carbon coating, leading to the formation of more orderly pyrolytic carbon (PyC) as a functional interlayer between fiber and matrix that could optimize the interfacial sliding strength in C/C composites. Effects of such a heat-treated PyC layers on the microstructure, tensile strength and fracture behavior of unidirectional C/C composites were investigated. Results showed that although the in-situ fiber strength was deteriorated after the introduction of interfacial layer, tensile strength of the specimen was greatly improved by 38.5% compared with pure C/C composites without any treatment. The interfacial sliding stress sharply decreased, which was interpreted from finite element analysis and verified by Raman spectra. Therefore, the fracture behavior was changed from brittle fracture to multiple-matrix cracking induced non-linear mechanical behavior. Finally, the ultimate strength can be predicted by different models according to the interfacial sliding stress. Our research would provide a meaningful way to improve both strength and toughness of C/C composites.

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    Strong and ductile Mg alloys developed by dislocation engineering
    M. Wang, B.B. He, M.X. Huang
    J. Mater. Sci. Technol., 2019, 35 (3): 394-395.  DOI: 10.1016/j.jmst.2018.09.033
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    Dislocation engineering concept has been successfully employed to tackle the strength-ductility trade-off in steels, resulting in the development of high-strength high-ductility deformed and partitioned (D&P) steel. The present perspective proposes to employ such dislocation engineering concept to develop strong and ductile magnesium (Mg) alloys. High density of??dislocations could be generated at appropriate temperature and retained in the Mg alloy after quenching to room temperature. Those??dislocations inherited from the warm deformation could provide??dislocation sources when the Mg alloy is deformed at room temperature, resulting in good ductility. The high dislocation density generated at warm deformation provides dislocation forest hardening, leading to improved yield strength of Mg alloy.

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    Resolution of a discrepancy of magnetic mechanism for Elinvar anomaly in Fe-Ni based alloys
    Fangyu Qin, Wenlong Xiao, Fengshuang Lu, Yuanchao Ji, Xinqing Zhao, Xiaobing Ren
    J. Mater. Sci. Technol., 2019, 35 (3): 396-401.  DOI: 10.1016/j.jmst.2018.09.032
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    Fe-Ni based Elinvar alloys performing temperature-independent elastic modulus over a wide temperature range have found wide and significant applications. Although numerous models involved with magnetism have been proposed to explain the Elinvar anomaly, some of the puzzles concerning the anomaly have not been fully understood. In this work, a remarkable discrepancy between the inflection temperature of modulus and the Curie temperature in a typical Fe-Ni-Cr Elinvar alloy was found, challenging the magnetic mechanism for Elinvar anomaly. Microstructural characterization and dynamic mechanical analysis demonstrate the occurrence of a strain glass transition with continuous formation of nanodomains. Accompanying such a transition, the gradual softening in the elastic modulus of austenite offsets the modulus hardening due to the vibrational anharmonicity of nanodomains upon cooling, leading to the Elinvar effect. As a result, the inflection temperature of modulus corresponds to the initiation of nanodomains’ formation instead of magnetic transition. Our findings specify the association of Elinvar anomaly with structural aspects, and provide new insights into the mechanism of Elinvar anomaly in Fe-Ni based alloy.

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    Interactions between dislocations and twins in deformed titanium aluminide crystals
    Guang Yang, Shang-Yi Ma, Kui Du, Dong-Sheng Xu, Sen Chen, Yang Qi, Heng-Qiang Ye
    J. Mater. Sci. Technol., 2019, 35 (3): 402-408.  DOI: 10.1016/j.jmst.2018.09.031
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    Using scanning, transmission electron microscopy and aberration-corrected scanning transmission electron microscopy, we have studied the interactions between dislocations and twins in impact deformed polysynthetic twinned TiAl crystal. The 1/3? dislocations with the coherent twin boundaries. An abnormal stacking fault was found adjacent to the coherent twin boundary. It has the same stacking sequence but different atom species in the [1ˉ10] direction with an additional displacement of 1/4[1ˉ10] in two neighboring {111} layers, and is likely induced by the slip of a 1/12[112] (i.e. 1/4[1ˉ10] + 1/6[21ˉ1]) dislocation.

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    Effect of thermal annealing on the microstructure, mechanical properties and residual stress relaxation of pure titanium after deep rolling treatment
    Jie Huang, Kai-Ming Zhang, Yun-Fei Jia, Cheng-Cheng Zhang, Xian-Cheng Zhang, Xian-Feng Ma, Shan-Tung Tu
    J. Mater. Sci. Technol., 2019, 35 (3): 409-417.  DOI: 10.1016/j.jmst.2018.10.003
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    The aim of this paper was to investigate the effect of thermal annealing on the microstructure, mechanical properties, and residual stress relaxation of deep rolled pure titanium. The microstructure and mechanical properties of the surface modified layer were analyzed by metallographic microscopy, transmission electron microscope and in-situ tensile testing. The results showed that the annealed near-surface layer with fine recrystallized grains had increased ductility but decreased strength after annealing below the recrystallization temperature, where the tensile strength was still higher than that of the substrate. After annealing at the recrystallization temperature, the recrystallized near-surface layer had smaller grain size, similar tensile strength, and higher proportional limit, comparable to those of the substrate. Moreover, the residual stress relaxation showed evidently different mechanisms at three different temperature regions: low temperature (T≤0.2Tm), medium temperature (T ≈ ( 0.2- 0.3)Tm), and high temperature (T ≥ 0.3Tm). Furthermore, a prediction model was proposed in terms of modification of Zener-Wert-Avrami model, which showed promise in characterizing the residual stress relaxation in commercial pure Ti during deep rolling at elevated temperature.

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    Effect of different surface treatments on bioactivity of porous titanium implants
    M. Todea, A. Vulpoi, C. Popa, P. Berce, S. Simon
    J. Mater. Sci. Technol., 2019, 35 (3): 418-426.  DOI: 10.1016/j.jmst.2018.10.004
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    The work aims to characterize the structure and to evaluate in vitro the effect of different surface treatments on the bioactivity of medical grade Ti6Al7Nb alloy implants manufactured by selective laser melting. In order to improve the bioactivity of these samples, they were subjected to heat treatment, chemical treatment, and impregnation with bioactive materials. To evaluate the apatite forming ability, the samples were immersed in simulated body fluid solution) and characterized before and after immersion by scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The composition and the texture of the surfaces after the applied treatments have a selective effect on apatite layer development on the surface of samples.

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    New insights into the in-process densification mechanism of cold spray Al coatings: Low deposition efficiency induced densification
    Richard Jenkins, Shuo Yin, Barry Aldwell, Morten Meyer, Rocco Lupoi
    J. Mater. Sci. Technol., 2019, 35 (3): 427-431.  DOI: 10.1016/j.jmst.2018.09.045
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    This work details new insights into the in-process densification mechanism of cold spray Al coatings. The results show a trend counter to common observations: coating plastic deformation levels and coating density decreases with an increase in particle impact velocity. A lower particle impact velocity and the consequent lower deposition efficiency (DE) results in greater tamping energy per unit volume of deposit, which is the primary reason for the observed trend. This is the first time that DE has been shown to have a non-linear impact on the density of a cold spray coating, with particle in-process tamping being the primary mechanism for coating densification.

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    Suppressing the anomalous rapid oxidation of Ti3AlC2 by incorporating TiB2
    Chao Li, Yuhai Qian, Chunlei Ma, Shumin Wang, Meishuan Li
    J. Mater. Sci. Technol., 2019, 35 (3): 432-439.  DOI: 10.1016/j.jmst.2018.08.002
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    The oxidation behavior of Ti3AlC2-20TiB2 composite was studied at 500?°C-900?°C in air. The composite showed a very low oxidation rate and followed a logarithmic oxidation law. The in-situ incorporation of TiB2 suppressed the anomalous rapid oxidation of the substrate Ti3AlC2 occurred near 600?°C by forming a protective B2O3 glass layer, and also improved the oxidation resistance of the MAX phase at intermediate-temperature.

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    Comparison of CMAS corrosion and sintering induced microstructural characteristics of APS thermal barrier coatings
    Yiyou Wu, Hua Luo, Canying Cai, Yanguo Wang, Yichun Zhou, Li Yang, Guangwen Zhou
    J. Mater. Sci. Technol., 2019, 35 (3): 440-447.  DOI: 10.1016/j.jmst.2018.09.046
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    The microstructural features of high-temperature sintered and CaO-MgO-Al2O3-SiO2 (CMAS) corroded air plasma sprayed Y2O3 stabilized ZrO2 (YSZ) thermal barrier coatings (TBCs) under the thermal gradient condition were comparatively studied. As-sprayed YSZ has a lamellar structure and the lamellae are composed of closely aligned columnar crystals. The sintered and the CMAS corroded YSZ coatings maintain the t’-ZrO2 phase as the as-sprayed YSZ coating. The sintered YSZ remains the lamellar structure with reduced interlamellar gaps and grains coarsening. After the CMAS corrosion, the top layer of the YSZ coating keeps its lamellar structure consisting of some columnar grains with the CMAS infiltration into the intergrain gaps and the formation of striped Zr2Y2O7. The typical lamellar structure transforms into more equiaxed grains in the middle and bottom layers of the ceramic coating along with significant infiltration of amorphous CMAS and anorthite formation in the bottom layer owing to the high contents of Ca and Al.

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    Tribocorrosion behavior in artificial seawater and anti-microbiologically influenced corrosion properties of TiSiN-Cu coating on F690 steel
    Fuliang Ma, Jinlong Li, Zhixiang Zeng, Yimin Gao
    J. Mater. Sci. Technol., 2019, 35 (3): 448-459.  DOI: 10.1016/j.jmst.2018.09.038
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    The TiSiN-Cu nanocomposite coating was deposited on F690 steel substrate by arc ion plating. The structure and composition, tribocorrosion behavior and anti-microbiologically influenced corrosion (MIC) properties of TiSiN-Cu coating were investigated. The results show that the TiSiN-Cu coating has unique nanocomposite structures. The results of tribocorrosion show that the potential and current change of F690 steel and TiSiN-Cu coatings tend to be opposite. The reason is that the F690 steel is non-passivated metal and the TiSiN-Cu coating has passivation phenomenon. The TiSiN-Cu coating possesses excellent tribocorrosion resistance. Cu ion released from TiSiN-Cu coating can effectively inhibit the corrosion caused by SRB.

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    Diffusion behavior of Cr in gradient nanolaminated surface layer on an interstitial-free steel
    S.L. Xie, Z.B. Wang, K. Lu
    J. Mater. Sci. Technol., 2019, 35 (3): 460-464.  DOI: 10.1016/j.jmst.2018.09.043
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    Nanolaminated structures composed of low-angle grain boundaries (LAGBs) possess high thermal stability. In this paper, a gradient nanolaminated (GNL) surface layer with smooth finish was fabricated on an interstitial-free steel by means of surface mechanical rolling treatment. Microstructural observations demonstrated that the average lamellar thickness is about 80?nm in the topmost surface layer and increases with increasing depth. High thermal stability was confirmed in the GNL surface layer after annealing at 500?°C. Diffusion measurements showed that effective diffusivity of Cr in GNL layer is 4-6 orders of magnitude higher than lattice diffusivity within the temperature range from 400 to 500?°C. This might be attributed to numerous LAGBs or dislocation structures with a higher energy state in the GNL surface layer. This work demonstrates the possibility to advanced chromizing (or other surface alloying) processes of steels with formation of GNL surface layer, so that a thicker alloyed surface layer with a stable nanostructure is achieved.

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CN: 21-1315/TG
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