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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      04 January 2019, Volume 35 Issue 1 Previous Issue    Next Issue
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    Orginal Article
    On the chemical compatibility between Zr-4 substrate and well-bonded Cr2AlC coating
    Jie Zhang, Zhilin Tian, Haibin Zhang, Lei Zhang, Jingyang Wang
    J. Mater. Sci. Technol., 2019, 35 (1): 1-5.  DOI: 10.1016/j.jmst.2018.09.005
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    Accident tolerant fuel (ATF) for the light water reactor has gained wide attentions after the Fukushima accident. To enhance the accident-tolerance of the nuclear system, one strategy is to modify the Zr-based alloy cladding surface with advanced ceramic coating. In this work, monolithic and dense Cr2AlC coating has been synthesized by magnetron sputtering. The as-grown Cr2AlC coating exhibits good chemical compatibility with Zr-based alloy substrate as well as mechanical integrity under both pull-off and scratch tests. The coating system also presents moderate thermochemical compatibility at 800?°C but degrades above 1000?°C under simulated loss-of-coolant accident (LOCA) conditions.

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    Optimizing mechanical property and cytocompatibility of the biodegradable Mg-Zn-Y-Nd alloy by hot extrusion and heat treatment
    Yiyuan Kang, Beining Du, Yueming Li, Baojie Wang, Liyuan Sheng, Longquan Shao, Yufeng Zheng, Tingfei Xi
    J. Mater. Sci. Technol., 2019, 35 (1): 6-18.  DOI: 10.1016/j.jmst.2018.09.020
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    The Mg-Zn-Y-Nd alloy is a new type of degradable material for biomedical application. In the present study, Mg-6Zn-1.2Y-0.8Nd alloy was fabricated, and then extrusion and heat treatment were conducted to optimize its mechanical properties and cytocompatibility. The microstructure observation, mechanical property, degradation behavior and cytocompatibility tests were conducted on the Mg-Zn-Y-Nd alloy with three different states: as-cast (alloy C), as-extruded (alloy E) and extruded + heat treated (alloy EH). The results show that alloy C consists of coarse grains and continuous secondary phases. The extrusion process has caused incomplete recrystallization, and results in a mixed grain structure of elongated grains and small equiaxed grains (alloy E). The heat treatment process has promoted the recrystallization and homogenized the grain structure (alloy EH). Both the strength and ductility of the alloy has been improved by extrusion, but the following heat treatment has decreased the strength and increased the ductility. The degradation behavior of the alloy C and E alloys does not show much difference, but improves slightly in alloy EH, because the heat treatment has homogenized the microstructure and released the residual stress in the alloy. The directly and indirectly cell viability tests indicate that alloy EH exhibits the best cytocompatibility, which should be ascribed to its relative uniform degradation and low ion releasing rate. In summary, the combination of hot extrusion and heat treatment could optimize the mechanical property and cytocompatibility of the Mg-Zn-Y-Nd alloy together, which is beneficial for the future application of the alloy.

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    A novel polymer critical re-melting treatment for improving corrosion resistance of magnesium alloy stent
    Shanshan Chen, Peng Wan, Bingchun Zhang, Deniz Eren Eris?en, Hui Yang, Ke Yang
    J. Mater. Sci. Technol., 2019, 35 (1): 19-22.  DOI: 10.1016/j.jmst.2018.09.021
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    Polymer coating was widely used as a protective coating on Mg alloy stent due to its excellent deformability. However, the polymer coating with lots of macro- and micro-holes after solvent evaporation during forming process would make corrosion medium permeate easier and decrease the corrosion resistance of Mg alloy stent. In this study, a novel critical re-melting method was adopted to improve the polymer coating densification, which was evaluated by the surface morphology of coating. The corrosion resistance of Mg alloy stent after critical re-melting treatment was examined by the electrochemical and immersion tests. The results indicated that the corrosion resistance of Mg alloy stent with polymer coating was improved significantly by polymer critical re-melting treatment.

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    An innovative method for the microstructural modification of TiAl alloy solidified via direct electric current application
    Zhanxing Chen, Hongsheng Ding, Ruirun Chen, Shiqiu Liu, Jingjie Guo, Hengzhi Fu
    J. Mater. Sci. Technol., 2019, 35 (1): 23-28.  DOI: 10.1016/j.jmst.2018.06.016
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    Ti-48Al-2Cr-2Nb alloy solidified with the application of direct electric current has a refined and homogeneous microstructure without segregation. We observed an initial decrease followed by a subsequent increase in grain size and lamellar spacing, with the increase in current density. Similar trend can also be obtained by varying the amount of α2-phase (Ti3Al). Using a directional solidification processing method, the columnar crystal microstructure transforms into an equiaxed crystal microstructure at a current density of 32-64?mA/mm2. High dislocation density is also introduced with a minimum cross-sectional grain size of 460?μm at a current density of 64?mA/mm2. The application of electric current alters the free energy of the critical nucleus and temperature via joule heating, causing a transformation from a columnar grain microstructure into an equiaxed grain microstructure. The increase in current density leads to a rise of the nucleation rate, and a resulting undercooling combined with temperature gradient contribute to growth of the primary phase, which finally results in grain coarsening at a critical current density of 96?mA/mm2. The climb and cross-slip of dislocation and the migration of grain boundary ultimately create variable lamellae spacing of TiAl alloy.

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    Welding solidification cracking susceptibility and behavior of a Ni-28W-6Cr alloy
    Shuangjian Chen, Xiang-Xi Ye, D.K.L. Tsang, Li Jiang, Kun Yu, Chaowen Li, Zhijun Li
    J. Mater. Sci. Technol., 2019, 35 (1): 29-35.  DOI: 10.1016/j.jmst.2018.09.013
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    Welding solidification cracking of alloys is associated with the range of solidification temperature that can be greatly affected by the amount of refractory metals and other additives. In this work, solidification cracking of Ni-28W-6Cr alloy with high W content was studied by gas tungsten arc welding, showing that the welding current, alloying elements and precipitates all affect the cracking susceptibility. The lengths of cracks increase linearly with the welding current in the range from 150 to 250?A. The relatively high cracking susceptibility is mainly attributed to the high content of Si, which tends to segregate with other elements including W, Cr, Mn as films or components with low melting point in the last solidification stage and weaken the binding force of grain boundaries. Moreover, the existence of precipitated continuous eutectic M6C carbides in the grain boundaries also acts as nucleation sites of crack initiation, and the cracks often propagate along solidification grain boundary.

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    Silica coating onto graphene for improving thermal conductivity and electrical insulation of graphene/polydimethylsiloxane nanocomposites
    Chaoxuan Shen, Han Wang, Tengxin Zhang, You Zeng
    J. Mater. Sci. Technol., 2019, 35 (1): 36-43.  DOI: 10.1016/j.jmst.2018.09.016
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    Graphene possess extremely high thermal conductivity, and they have been regarded as prominent candidates to be used in thermal management of electronic devices. However, addition of graphene inevitably causes dramatic decrease in electrical insulation, which is generally unacceptable for thermal interface materials (TIMs) in real electronic industry. Developing graphene-based nanocomposites with high thermal conductivity and satisfactory electrical insulation is still a challenging issue. In this study, we developed a novel hybrid nanocomposite by incorporating silica-coated graphene nanoplatelets (Silica@GNPs) with polydimethylsiloxane (PDMS) matrix. The obtained Silica@GNP/PDMS composites showed satisfactory electrical insulation (electrical resistivity of over 1013 Ω?cm) and high thermal conductivity of 0.497?W?m-1?K-1, increasing by 155% compared with that of neat PDMS, even higher than that of GNP/PDMS composites. Such high thermal conductivity and satisfactory electrical insulation is mainly attributed to the insulating silica-coating, good compatibility between components, strong interfacial bonding, uniform dispersion, and high-efficiency heat transport pathways. There is great potential for the Silica@GNP/PDMS composites to be used as high-performance TIMs in electronic industry.

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    Highly collective atomic transport mechanism in high-entropy glass-forming metallic liquids
    Changjiu Chen, Kaikin Wong, Rithin P. Krishnan, Lei Zhifeng, Dehong Yu, Zhaoping Lu, Suresh M. Chathoth
    J. Mater. Sci. Technol., 2019, 35 (1): 44-47.  DOI: 10.1016/j.jmst.2018.09.008
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    Quasielastic neutron scattering (QENS) has been used to study the atomic relaxation process and microscopic transport mechanism in high-entropy glass-forming metallic (HE-GFM) liquids. Self-intermediate scattering functions obtained from the QENS data show unusually large stretching, which indicates highly heterogeneous atomic dynamics in HE-GFM liquids. In these liquids, a group of atoms over a length scale of about 21?? diffuses collectively even well above the melting temperature. However, the temperature dependence of diffusion process in one of the HE-GFM liquid is Arrhenius, but in the other HE-GFM liquid it is non-Arrhenius. Although the glass-forming ability of these HE-GFM liquids is very poor, the diffusion coefficients obtained from the QENS data indicate the long range atomic transport process is much slower than that of the best metallic glass-forming liquids at their melting temperatures.

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    Dependence of mechanical properties on the microstructure characteristics of a near β titanium alloy Ti-7333
    Ruifeng Dong, Jinshan Li, Hongchao Kou, Jiangkun Fan, Bin Tang
    J. Mater. Sci. Technol., 2019, 35 (1): 48-54.  DOI: 10.1016/j.jmst.2018.06.018
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    In this work, the microstructure and the corresponding tensile properties of the rolled Ti-7Mo-3Nb-3Cr-3Al (Ti-7333) alloy before and after the thermal treatments were investigated. The results show that a strong α-fiber texture is developed in the rolled Ti-7333 alloy. The deformed matrix and the texture significantly induce the variant selection of α phase. The high strength of the rolled Ti-7333 alloy is attributed to the <110> texture parallel to the tensile direction and the dispersed α phase within the matrix. After the solution treatment followed by the aging treatment, the texture decreases and the microstructure consists of the equiaxed β grains, the spheroidal αp phase and various needle-like α variants. Eventually, the alloy could achieve an optimal combination with the strength of about 1450?MPa, the ductility of about 10.5% and a considerable shear strength of about 775?MPa. This balance can be ascribed to the performance of the spheroidal αp phase and various needle-like αs variants. The results indicate that the Ti-7333 alloy could be a promising candidate material for the high-strength fastener.

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    An improved process for grain refinement of large 2219 Al alloy rings and its influence on mechanical properties
    Hailin H, Youping Yi, Shiquan Huang, Yuxun Zhang
    J. Mater. Sci. Technol., 2019, 35 (1): 55-63.  DOI: 10.1016/j.jmst.2018.09.007
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    The large 2219 Al alloy rings used to connect propellant tank components of a satellite launch vehicle to each other are conventionally manufactured by radial-axial ring rolling at 460 °C with 50% deformation, but often suffer from coarse elongated grain and low ductility. An improved process (hot ring rolling at 460 °C with 30% deformation, then air cooling to 240 °C, followed by ring rolling at 240 °C with 20% deformation) was tested for ring manufacturing. The corresponding microstructure evolution and mechanical properties of the produced rings were studied. The results show that the improved process can successfully be applied to manufacture the large 2219 Al alloy rings without formation of macroscopic defects, resulting in a product with fine and uniform grains after heat treatment. The fracture mechanism of both rings was mainly intergranular fracture. With the resulting grain size refinement due to the improved process, more homogeneous slip occured and the crack propagation path became more tortuous during the tensile testing process. Thus, the elongation in all three orthogonal directions was greatly improved, and the axial elongation increased from 3.5% to 10.0%.

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    Effect of tannic acid on corrosion behavior of carbon steel in NaCl solution
    Wenhua Xu, En-Hou Han, Zhenyu Wang
    J. Mater. Sci. Technol., 2019, 35 (1): 64-75.  DOI: 10.1016/j.jmst.2018.09.001
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    Corrosion behavior of unrusted Q235 carbon steel was investigated in 3.5% NaCl solutions with 1-5?wt% tannic acid addition, using electrochemical methods including electrochemical impedance spectra (EIS), potentiodynamic polarization and scanning vibrating electrode technique (SVET) combined with surface analysis. Results show that the corrosion rate decreases with increasing tannic acid concentration. As compared with tannic acid-free solution, 1% tannic acid does not provide inhibition effect during the whole immersion, while inhibition effect is observed for 3% tannic acid after 8?h and for 5% tannic acid after 4?h. The inhibition efficiency by weight loss measurements (ηw) for 1%, 3%, and 5% tannic is around -17.2%, 40.3%, and 51.5%, respectively. Corrosion of unrusted carbon steel in the presence of tannic acid is attributed to the joint effect of tannic acid adsorption and pH decrease. Formation of ferric-tannates is verified by X-ray photoelectron spectroscopy (XPS) and Raman spectra. The reaction mechanism between tannic acid and unrusted carbon steel is proposed.

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    The combined effects of grain and sample sizes on the mechanical properties and fracture modes of gold microwires
    H.K. Yang, K. Cao, Y. Han, M. Wen, J.M. Guo, Z.L. Tan, J. Lu, Y. Lu
    J. Mater. Sci. Technol., 2019, 35 (1): 76-83.  DOI: 10.1016/j.jmst.2018.09.012
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    Hall-Petch relation was widely applied to evaluate the grain size effect on mechanical properties of metallic material. However, the sample size effect on the Hall-Petch relation was always ignored. In the present study, the mechanical test and microstructure observation were performed to investigate the combined effects of grain and sample sizes on the deformation behaviors of gold microwires. The polycrystalline gold microwires with diameter of 16 μm were annealed at temperatures from 100?°C to 600?°C, leading to different ratios (t/d) of wire diameter (t) to grain size (d) from 0.9 to 16.7. When the t/d was lower than 10, the yield stress dropped fast and deviated from the Hall-Petch relation. The free-surface grains played key role in the yield stress softening, and the volume fraction of free-surface grains increased with the t/d decreasing. Furthermore, the effects of t/d on work-hardening behaviors and fracture modes were also studied. With t/d value decreasing from 17 to 3.4, the samples exhibited necking fracture and the dislocation pile-ups induced work-hardening stage was gradually activated. With the t/d value further decreasing (t/d3.4), the fracture mode turned into shear failure, and the work-hardening capability lost. As the gold microwire for wire bonding is commonly applied in the packaging of integrated circuit chips, and the fabrication of microwire suffers multi-pass cold-drawing and annealing treatments to control the grain size. The present study could provide instructive suggestion for gold microwire fabrication and bonding processes.

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    On the γ′ precipitates of the normal and inverse Portevin-Le Châtelier effect in a wrought Ni-base superalloy
    Xinguang Wang, Guoming Han, Chuanyong Cui, Shuai Guan, Jinguo Li, Guichen Hou, Yizhou Zhou, Xiaofeng Sun
    J. Mater. Sci. Technol., 2019, 35 (1): 84-87.  DOI: 10.1016/j.jmst.2018.09.014
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    The Portevin-Le Chatelier (PLC) effects in a wrought Ni-base superalloy with different γ? precipitates contents have been investigated. Detailed analysis on the serration type of the tensile curves indicates that the γ? precipitates have a decisive influence on the transformation from normal to inverse PLC behavior, which is rarely proposed in other works. It is considered that the γ? precipitates play the same role in PLC effect as temperature and strain rate for the investigated wrought Ni-base superalloy.

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    Measurement of interfacial residual stress in SiC fiber reinforced Ni-Cr-Al alloy composites by Raman spectroscopy
    Xixi Niu, Haoqiang Zhang, Zhiliang Pei, Nanlin Shi, Chao Sun, Jun Gong
    J. Mater. Sci. Technol., 2019, 35 (1): 88-93.  DOI: 10.1016/j.jmst.2018.09.023
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    Raman spectroscopy was used to measure Raman spectra of the inner SiC fibers and surface C-rich layers of SiC fibers, composite precursors and SiCf/Ni-Cr-Al composites. The residual stresses of the inner SiC fibers and surface C-rich layers were calculated, and the effect of the (Al?+?Al2O3) diffusion barrier layer on the interfacial residual stress in the composites was analyzed in combination with the interface microstructure and energy disperse spectroscopy (EDS) elements lining maps. The results show that the existence of (Al?+?Al2O3) diffusion barrier improves the compatibility of the SiCf/Ni-Cr-Al interface, inhibits the adverse interfacial reaction, and relieves the residual stress inside SiC fibers and at the interface of composite material. Heat treatment can reduce the residual stress at the interface. As the heat treatment time increases, the residual stress at the interface decreases.

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    A general strategy for the reliable joining of Al/Ti dissimilar alloys via ultrasonic assisted friction stir welding
    Zhongwei Ma, Yanye Jin, Shude Ji, Xiangchen Meng, Lin Ma, Qinghua Li
    J. Mater. Sci. Technol., 2019, 35 (1): 94-99.  DOI: 10.1016/j.jmst.2018.09.022
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    Ultrasonic assisted friction stir welding (UaFSW) was used to join 6061-T6 aluminum and Ti6Al4V alloys. A small plunge depth endowed with the low heat input was used and the sound joints without obvious thickness reduction were achieved. A diffusion-type bonding without the intermetallic compounds layer was observed at the joint interface. The ultrasonic improved the diffusion thickness and decreased the average size of grains and titanium alloy fragments. A hook-like structure was formed at the bottom interface of the UaFSW joint, which improved the bonding length and the mechanical interlocking. The microhardness of the stir zone was increased because of the further grain refinement induced by ultrasonic. The maximum tensile strength of the UaFSW joint was 236 MPa, which reached 85% of the base 6061-T6 alloy.

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    Metal-organic frameworks derived flower-like Co3O4/nitrogen doped graphite carbon hybrid for high-performance sodium-ion batteries
    Haifeng Xu, Guang Zhu, Baoming Hao
    J. Mater. Sci. Technol., 2019, 35 (1): 100-108.  DOI: 10.1016/j.jmst.2018.09.019
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    In this work, a novel flower-like cobalt-based metal organic frameworks (MOFs) self-assembled by Co2+ and nicotinic acid have been designed and synthesized. After a simple annealing treatment, Co3O4 nanoparticles in-situ decorating on nitrogen doped graphite carbon-sheet (Co3O4/NC) were obtained. The resultant Co3O4/NC hybrid with unique flower-like structure and ration combination of Co3O4 nanoparticles and nitrogen doped graphite carbon, endowing the hybrid with enhanced electrical conductivity, short ion diffusion pathways and rich porosity to the materials, which can largely alleviate the problems of Co3O4 such as inferior intrinsic electrical conductivity, sluggish ion kinetics and large volume change upon cycling. When evaluated as anode material for sodium-ion batteries (SIBs), the Co3O4/NC hybrid exhibits satisfied reversible capacity (213.9?mAh g-1 after 100 cycles at 0.1?A?g-1), excellent rate capability (145.4?mAh?g-1 at 2?A?g-1 and 130.1?mAh?g-1 at 4?A?g-1) and robust long-term cycling stability (120.1?mAh?g-1 after 2000 cycles at 0.5?A?g-1), showing great potential for high-performance SIBs.

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    Effects of d-Phenylalanine as a biocide enhancer of THPS against the microbiologically influenced corrosion of C1018 carbon steel
    Jin Xu, Ru Jia, Dongqing Yang, Cheng Sun, Tingyue Gu
    J. Mater. Sci. Technol., 2019, 35 (1): 109-117.  DOI: 10.1016/j.jmst.2018.09.011
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    Microbiologically influenced corrosion (MIC) is caused by biofilms such as those of sulfate reducing bacteria (SRB). To mitigate MIC, biocide treatment is often needed. Tetrakis (hydroxymethyl) phosphonium sulfate (THPS) is an environmentally friendly biocide that is often used in the oil and gas industry. However, its prolonged use leads to biocide resistance, leading to dosage escalation. A biocide enhancer can be used to slow down the trend. In recent years, d-amino acids have been investigated as an enhancer for THPS and other biocides. Published works used anaerobic vials and flow devices, which could not reveal the real-time changes of the biocide treatment on corrosion. In this work, it was proven that the biocide enhancement effects of d-Phenylalanine (d-Phe) on THPS against the Desulfovibrio vulgaris biofilm on C1018 carbon steels could be assessed in real time using linear polarization resistance and electrochemical impedance spectroscopy to collaborate sessile cell count, weight loss and pitting depth data. The results showed that 500?ppm (w/w) d-Phe effectively enhanced 80?ppm THPS against MIC by the D. vulgaris (a corrosive SRB) biofilm. The sessile cell count and pit depth were all reduced with the enhancement of d-Phe.

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    Structure modification and recovery of amorphous Fe73.5Si13.5B9Nb3Cu1 magnetic ribbons after autoclave treatment: SAXS and thermodynamic analysis
    L.Y. Guo, X. Wang, K.C. Shen, K.B. Kim, S. Lan, X. WangL., W.M. Wang
    J. Mater. Sci. Technol., 2019, 35 (1): 118-126.  DOI: 10.1016/j.jmst.2018.09.010
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    The structure, crystallization kinetics and magnetic property of as-quenched Fe73.5Si13.5B9Nb3Cu1 amorphous ribbon (R0) as well as ribbons after autoclave treatment at 100?°C and 150?°C (R1 and R2) have been systematically studied by various techniques. With increasing autoclave treatment temperature, the measured structural, kinetic and magnetic parameters of samples increase firstly, i.e. R0?rM) MRO (medium range order), but increase the small rM MRO. The measured structural, thermal and magnetic parameters of R2 sample have a tendency to recover toward as-quenched R0 sample. The thermal and magnetic parameters of samples after solely annealing treatment at higher temperature have no obvious recover phenomenon. The uneven actions of pressure and temperature in autoclave treatment may be helpful for us to search a new method to improve the magnetic properties of Fe-based glasses.

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    Lattice dynamics of FeMnP0.5Si0.5 compound from first principles calculation
    B. Wurentuya, Shuang Ma, B. Narsu, O. Tegus, Zhidong Zhang
    J. Mater. Sci. Technol., 2019, 35 (1): 127-133.  DOI: 10.1016/j.jmst.2018.09.009
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    Understanding the role of lattice vibrations on first-order magnetic transitions is essential for their fundamental description, as well as for the optimization of the related functional properties. Here, we present a first principles study on the lattice dynamics of the MnFeP0.5Si0.5 compound. The phonon spectra are obtained by Density Functional Theory (DFT) calculations in combination with frozen phonon method. DFT calculations reproduce most of the features observed in experiments including the lattice softening across the magnetic phase transition and the pronounced shift of phonon peak. The site projected phonon density of states (pDOS) shows that the local vibrations of Mn atoms have an essential contribution to the overall lattice softening. Moreover, the local lattice vibrations of Mn atoms are rather featureless in the paramagnetic state (PM) and thus the total pDOS evolution across the transition appears to be dominated by Fe. The lattice vibrations of both Fe and Mn in the PM state are very sensitive to the local environment, which shows that the magnetic order and the local chemical environment are strongly coupled in this compound.

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    Influence of phosphorous on nucleation and growth of grains during solidification in a NiCrFe alloy
    Xintong Lian, Wenru Sun, Litao Chang, Fang Liu, Xin Xin
    J. Mater. Sci. Technol., 2019, 35 (1): 134-141.  DOI: 10.1016/j.jmst.2018.07.001
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    The influence of phosphorus on the solidification of a NiCrFe model alloy has been investigated through a series of analytical techniques. It was found that increasing phosphorous additions greatly influenced the as-cast microstructure, changing from equiaxed grains to columnar grains in the center of ingots. It is indicated that the increase of phosphorous reduced the nucleation of grains and promoted dendrite growth during solidification. Furthermore, the addition of phosphorus in alloys also caused the segregation and phase transformation at grain boundaries and in interdendritic regions. The mechanism by which phosphorus influence the solidification of alloys was discussed based on experimental results as well.

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    Strain hardening of as-extruded Mg-xZn (x = 1, 2, 3 and 4 wt%) alloys
    Chaoyue Zhao, Xianhua Chen, Fusheng Pan, Jingfeng Wang, Shangyu Gao, Teng Tu, Chunquan Liu, Jiahao Yao, Andrej Atrens
    J. Mater. Sci. Technol., 2019, 35 (1): 142-150.  DOI: 10.1016/j.jmst.2018.09.015
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    The influence of Zn on the strain hardening of as-extruded Mg-xZn (x?=?1, 2, 3 and 4?wt%) magnesium alloys was investigated using uniaxial tensile tests at 10-3 s-1 at room temperature. The strain hardening rate, the strain hardening exponent and the hardening capacity were obtained from true plastic stress-strain curves. There were almost no second phases in the as-extruded Mg-Zn magnesium alloys. Average grain sizes of the four as-extruded alloys were about 17.8?μm. With increasing Zn content from 1 to 4?wt%, the strain hardening rate increased from 2850?MPa to 6810?MPa at (σ-σ0.2)?=?60?MPa, the strain hardening exponent n increased from 0.160 to 0.203, and the hardening capacity, Hc increased from 1.17 to 2.34. The difference in strain hardening response of these Mg-Zn alloys might be mainly caused by weaker basal texture and more solute atoms in the α-Mg matrix with higher Zn content.

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    Surface charge induced tuning of electrical properties of CVD assisted graphene and functionalized graphene sheets
    Manash Jyoti Deka, Devasish Chowdhury
    J. Mater. Sci. Technol., 2019, 35 (1): 151-158.  DOI: 10.1016/j.jmst.2018.09.017
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    We demonstrate a new approach to tune the electrical properties of graphene and functionalized graphene. Graphene was synthesized using thermal chemical vapour deposition (TCVD) method on copper foil using precursor gas acetylene and co-catalyst H2 gas. TCVD assisted graphene was successfully transferred onto a silicon wafer. Transferred graphene sheet was then functionalized to prepare graphene oxide (GO) and reduced graphene oxide (rGO). Different surface charge carbon nanoparticles, e.g. carbon nanoparticle with net positive charge and carbon nanoparticle with net negative charge were then immobilized on transferred graphene and functionalized graphene sheets. The functionalized graphene and charge mobilized functionalized graphene were characterized by Uv-vis spectroscopy, Fourier transformed infrared spectroscopy, scanning electron microscopy, and Raman spectroscopy. After immobilization of carbon nanomaterials, the ac electrical conductivity was found to increase due to enhancement of the surface charge, electron density, and mobility. It was observed that negative surface charge immobilized graphene and functionalized graphene show higher conductivity. Thus, the electrical property of graphene and functionalized graphene can be tuned by surface modification with different surface charge carbon nanomaterials.

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    A comparative study of Ni/Al2O3-SiC foam catalysts and powder catalysts for the liquid-phase hydrogenation of benzaldehyde
    Kai Li, Yilai Jiao, Zhenming Yang, Jinsong Zhang
    J. Mater. Sci. Technol., 2019, 35 (1): 159-167.  DOI: 10.1016/j.jmst.2018.09.018
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    In this study, Al2O3-washcoated SiC (Al2O3-SiC) foams and Al2O3 powder were employed as the supports of a Ni catalyst for the liquid-phase hydrogenation of benzaldehyde. A series of Ni/Al2O3-SiC foam catalysts and Ni/Al2O3 powder catalysts with a Ni loading from 10?wt% to 37?wt% of the weight of Al2O3 were first prepared by a deposition-precipitation (DP) method. The catalytic activity and recyclability of both kinds of catalysts were then compared. Although it had a smaller accessible surface area with the reactant, the foam catalyst with a Ni loading of 16?wt% exhibited a slightly higher conversion of benzaldehyde after 6?h (of 99.3%) in comparison with the Ni/Al2O3 catalyst with identical Ni loading (conversion of 97.5%). When the Ni loading increased from 16?wt% to 37?wt%, the reaction rate obtained with the foam catalyst increased significantly from 0.108 to 0.204?mol?L-1?h-1, whereas the reaction rate obtained with the powder catalyst increased from 0.106 to 0.123?mol?L-1?h-1. Furthermore, the specific activity (moles of benzaldehyde consumed by 1?g?min-1 of Ni) of the foam catalyst with a Ni loading above 30?wt% was superior to that of the powder catalyst because of its smaller Ni-particle size and higher mass-transfer rate. The foam catalyst displayed a high recyclability as a function of run times owing to the strong interaction between the Ni component and the Al2O3 coating. The conversion of benzaldehyde over the foam catalyst remained almost unchanged after being used 8 times. In comparison, a drop of 43% in the conversion of benzaldehyde with the powder catalyst was observed after being used 7 times due to the leaching of the Ni component.

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    Modeling the corrosion behavior of Ni-Cr-Mo-V high strength steel in the simulated deep sea environments using design of experiment and artificial neural network
    Qiangfei Hu, Yuchen Liu, Tao Zhang, Shujiang Geng, Fuhui Wang
    J. Mater. Sci. Technol., 2019, 35 (1): 168-175.  DOI: 10.1016/j.jmst.2018.06.017
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    Corrosion in complex coupling environments is an important issue in corrosion field, because it is difficult to take into account a large number of environment factors and their interactions. Design of Experiment (DOE) can present a methodology to deal with this difficulty, although DOE is not commonly spread in corrosion field. Thus, modeling corrosion of Ni-Cr-Mo-V steel in deep sea environment was performed in order to provide example demonstrating the advantage of DOE. In addition, an artificial neural network mapping using back-propagation method was developed for Ni-Cr-Mo-V steel such that the ANN model can be used to predict polarization curves under different complex sea environments without experimentation. Furthermore, roles of environment factors on corrosion of Ni-Cr-Mo-V steel in deep sea environment were discussed.

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    A flexible conductive hybrid elastomer for high-precision stress/strain and humidity detection
    Haoran Liu, Zhenyi Zhang, Jun Ge, Xiao Lin, Xinye Ni, Huilin Yang, Lei Yang
    J. Mater. Sci. Technol., 2019, 35 (1): 176-180.  DOI: 10.1016/j.jmst.2018.09.006
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    Flexible and environment-responsive materials are essential for a large number of applications from artificial skin to wearable devices. The present study develops a flexible, ultra-low cost conductive hybrid elastomer (CHE), which possesses high responsive capabilities to stress/strain and humidity. CHE was composed of polydimethylsiloxane (PDMS) and starch hydrogel (SH), enabling great elasticity (56?kPa), high conductivity (10-2 S/m) and high sensitivity to external stimuli (gauge factor of CHE under stress and strain are 0.71 and 2.22, respectively, and sensitivity to humidity is 1.2?×?10-6 S/m per RH%). These properties render CHE a promising candidate for artificial skin and wearable electronics applications of continuously monitoring environmental information.

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    Effect of refinement of grains and icosahedral phase on hot compressive deformation and processing maps of Mg-Zn-Y magnesium alloys with different volume fractions of icosahedral phase
    T.Y. Kwak, W.J. Kim
    J. Mater. Sci. Technol., 2019, 35 (1): 181-191.  DOI: 10.1016/j.jmst.2018.06.019
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    The effect of the volume fraction of I-phase on the hot compressive behavior and processing maps of the extruded Mg-Zn-Y alloys was examined, and the obtained results were compared with those of the cast alloys in a previous work. The average grain sizes, fractions of dynamically recrystallized (DRXed) grains, and sizes of DRXed grains of the extruded alloys after compressive deformation were significantly smaller, higher and smaller, respectively, than those of the cast alloys after compressive deformation under the same experimental conditions. This was because the microstructures of the extruded alloys, having much more grain boundaries and more refined I-phase particles than the cast alloys, provided a larger number of nucleation sites for dynamic recrystallization than those of the cast alloys. The constitutive equations for high-temperature deformation of the extruded and cast alloys could be derived using the same activation energy for plastic flow, which was close to the activation energy for lattice diffusion in magnesium. Compared with the cast alloys, the onset of the power law breakdown (PLB) occurred at larger Zener-Holloman (Z) parameter values in the extruded alloys. This was because the extruded alloys had finer initial grain sizes and higher fractions of finer DRXed grains compared to the cast alloys, such that the onset of PLB caused by creation of excessive concentrations of deformation-induced vacancies was delayed to a higher strain rate and a lower temperature. The flow-stress difference between the extruded alloys and the cast alloys could be attributed to the difference in the fraction of DRXed grains. According to the processing maps, the extruded alloys exhibited higher power dissipation efficiency and flow stability than the cast alloys. This agreed with the microstructural observations.

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    Experimental and numerical investigations of bonding interface behavior in stationary shoulder friction stir lap welding
    Q. Wen, W.Y. Li, W.B. Wang, F.F. Wang, Y.J. Gao, V. Patel
    J. Mater. Sci. Technol., 2019, 35 (1): 192-200.  DOI: 10.1016/j.jmst.2018.09.028
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    Stationary shoulder friction stir lap welding (SSFSLW) was employed to weld 2024 aluminum alloy. A coupled Eulerian-Lagrangian (CEL) model was developed to investigate the lap interface behavior during SSFSLW. Numerical results of material movement and equivalent plastic strain were in good agreement with the experimental work. With increasing welding speed, the distances from the hook tip to the top surface of the upper workpiece on the retreating side (RS) and the advancing side (AS) increase, while the distance between two wave-shaped alclads decreases. A symmetric interface bending is observed on the AS and the RS during plunging, while the interface bending on the AS is bigger than that on the RS during welding. The peak temperature of the interface on the AS is higher than that on the RS. The equivalent plastic strain gradually increases as the distance to the weld center decreases, and its peak value is obtained near the bottom of the weld.

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    Nucleation of dislocations and twins in fcc nanocrystals: Dynamics of structural transformations
    Aleksandr V. Korchuganov, Aleksandr N. Tyumentsev, Konstantin P. Zolnikov, Igor Yu. Litovchenko, Dmitrij S. Kryzhevich, Elazar Gutmanas, Shouxin Li, Zhongguang Wang, Sergey G. Psakhie
    J. Mater. Sci. Technol., 2019, 35 (1): 201-206.  DOI: 10.1016/j.jmst.2018.09.025
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    This paper reports on a molecular dynamics study of structural rearrangements in a copper nanocrystal during nucleation of plastic deformation under uniaxial tension. The study shows that the resulting nucleation of partial dislocations on the free surface and their glide occurs through local fcc→bcc→hcp transformations via consistent atomic displacements. We propose an atomic model for the generation of dislocations and twins based on local reversible fcc→bcc→fcc transformations, with the reverse one proceeding through an alternative system. The model gives an insight into possible causes and mechanisms of the generation of partial dislocations and mechanical twins in two and more adjacent planes of plastically deformed nanocrystals. The obtained data allow a better understanding of how plasticity is generated in nanostructured materials.

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    Novel transcatheter aortic heart valves exhibiting excellent hemodynamic performance and low-fouling property
    F. Guo, K. Jiao, Y. Bai, J. Guo, Q. Chen, R. Yang, X. Zhang
    J. Mater. Sci. Technol., 2019, 35 (1): 207-215.  DOI: 10.1016/j.jmst.2018.09.026
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    Transcatheter aortic heart valves (TAHVs) have been widely used for aortic valve replacements, with less trauma and lower clinical risk compared with traditional surgical heart valve replacements. In the present study, composites of poly(ethylene glycol) diacrylate (PEGDA) hydrogels and anisotropic high-shrinkage polyethylene terephthalate/polyamide6 (PET-PA6) fabric (PEGDA/PET-PA6) were fabricated as artificial heart valve leaflets. Dynamic mechanical analyses (DMA) indicated that PEGDA/PET-PA6 composites possessed anisotropic mechanical properties (i.e., storage moduli ~23.30 ± 1.36 MPa parallel to the aligned fabric fibers and ~9.68 ± 0.90 MPa perpendicular to the aligned fibers at 1 Hz) that were comparable to aortic valve leaflets. The PEGDA/PET-PA6 composites with smooth surfaces were highly hydrophilic (contact angle ~41.6° ± 3.8°) and had low-fouling properties without platelet adhesion, suggesting a low risk of thrombogenicity when they interacted with blood. Furthermore, transcatheter aortic heart valves were fabricated using nitinol self-expanding frames and PEGDA/PET-PA6 composites as artificial leaflets, which presented excellent hemodynamic performance with a large orifice area (1.75 cm2) and low regurgitation (3.41%), thus meeting the requirements of ISO 5840-3 standard. Therefore, PEGDA/PET-PA6 composites had suitable mechanical properties, good biocompatibility, and low-fouling properties, indicating that they might be used for TAHVs in the future.

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    Microbiologically influenced corrosion of titanium caused by aerobic marine bacterium Pseudomonas aeruginosa
    M. Saleem Khan, Zhong Li, Ke Yang, Dake Xu, Chunguang Yang, Dan Liu, Yassir Lekbach, Enze Zhou, Phuri Kalnaowakul
    J. Mater. Sci. Technol., 2019, 35 (1): 216-222.  DOI: 10.1016/j.jmst.2018.08.001
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    Microbiologically influenced corrosion (MIC) is a big threat to the strength and safety of many metallic materials used in different environments throughout the world. The metabolites and bioactivity of the microorganisms cause severe deterioration on the metals. In this study, MIC of pure titanium (Ti) was studied in the presence of a highly corrosive aerobic marine bacterium Pseudomonas aeruginosa. The results obtained from electrochemical test showed that Ti was corrosion resistant in the abiotic culture medium after 14 d, while the increased corrosion current density (icorr) obtained from polarization curves and the decreased charge transfer resistance (Rct) from electrochemical impedance spectroscopy (EIS) indicated the accelerated corrosion of Ti caused by P. aeruginosa biofilm. For further confirmation of the above results, the surface of Ti was investigated using scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and X-ray photoelectron spectroscopy (XPS). According to the XPS results, TiO2 was formed in both abiotic and biotic conditions, while unstable oxide Ti2O3 was detected in the presence of P. aeruginosa, leading to the defects in the passive film and localized corrosion. Pitting corrosion was investigated with the help of CLSM, and the largest pit depth found on Ti surface immersed in P. aeruginosa was 1.2 μm. Ti was not immune to MIC caused by P. aeruginosa.

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    A modified θ projection model for constant load creep curves-I. Introduction of the model
    Chao Fu, Yadong Chen, Xiaofei Yuan, Sammy Tin, Stoichko Antonov, Koichi Yagi, Qiang Feng
    J. Mater. Sci. Technol., 2019, 35 (1): 223-230.  DOI: 10.1016/j.jmst.2018.09.024
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    Estimating long-term creep deformation and life of materials is an effective way to ensure the service safety and to reduce the cost of long-term integrity evaluation of high temperature structural materials. Since the 1980s, the θ projection model has been widely used for predicting creep lives due to its ability to capture the characteristic transitions observed in creep curves obtained under constant true stress conditions. However, the creep rupture behavior under constant load or engineering stress conditions cannot be simulated accurately using this model because of the different stress states. In this paper, creep curves obtained under constant load conditions were analyzed using a modified θ projection model by considering the increase in true stress with creep deformation during the creep tests. This model is expressed as ε=θ11-e-θ2t+θ3eθ4eθ5εt-1, and was validated using the creep curves of K465 and DZ125 superalloys tested at a range of temperatures and engineering stresses. Moreover, it was shown that the predictive capability of the modified θ projection model was significantly improved over the original one, as it reduces the prediction uncertainty from a range of 10% to 20% to below 5%. Meanwhile, it was shown that the model can be reasonably used for predicting constant stress creep conditions, when appropriate parameters are used. The prediction performance of the modified model will be discussed in another paper. The results of this study show great potential for the evaluation and assessment of the service safety of structural materials used in applications where designs are limited by creep deformation.

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