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CN 21-1315/TG
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Current Issue
 15 March 2020, Volume 41 Issue 0 Previous Issue    Next Issue
Research Article
 Select Evolution of microstructure and tensile properties of cold-drawn hyper-eutectoid steel wires during post-deformation annealing Majid Jafari, Chan-Woo Bang, Jong-Chan Han, Kyeong-Min Kim, Seon-Hyeong Na, Chan-Gyung Park, Byeong-Joo Lee J. Mater. Sci. Technol., 2020, 41 (0): 1-11.  DOI: 10.1016/j.jmst.2019.08.054 Manufacturing temperatures of severely cold-drawn hyper-eutectoid steel wires are sufficiently high to influence the mobility of dislocations and alloy elements, thereby affecting the materials’ mechanical properties. Herein, we describe the evolution of microstructure and tensile strength of the as-drawn 3.45 GPa steel wire during post-deformation annealing for 30 min at 150-450 °C. Annealing at 150 °C raised the strength to 3.77 GPa by age-hardening through activation of dislocations pinning by carbon, while further temperature rising up to 450 °C caused a severe loss of strength. It was proved that annealing at 300 and 450 °C destabilizes the lamellar microstructure, promoting the formation of carbon-deficient (Fe,Mn,Cr)3C-type cementite particles with preferentially rounded and partially faceted hetero-interfaces. Annealing at 450 °C yielded the accumulation of Mn and Cr at the ferrite/particle interfaces, and their concentrations at the interfaces were dependent on the interface structure; i.e., lower concentrations at rounded interfaces (formed through capillarity-driven coarsening of the spheroidized cementite), and higher concentrations at faceted interfaces (that are initially existing in the as-drawn state). Our proof-of-principle observations, supported by thermodynamic calculations and kinetic assessments, provide a pathway for understanding the changes in microstructural and tensile properties during manufacturing of the hyper-eutectoid steel wires.
 Select Improvement in varistor properties of CaCu3Ti4O12 ceramics by chromium addition Edson Cezar Grzebielucka, João Frederico Haas Leandro Monteiro, Eder Carlos Ferreira de Souza, Christiane Philippini Ferreira Borges, André Vitor Chaves de Andrade, Eloísa Cordoncillo, Héctor Beltrán-Mir, Sandra Regina Masetto Antunes J. Mater. Sci. Technol., 2020, 41 (0): 12-20.  DOI: 10.1016/j.jmst.2019.08.055 The effect of chromium addition on the structure and electrical properties of CaCu3Ti4O12 is studied. Compositions based on the formula CaCu3Ti4-xCrxO12-δ (x = 0, 0.025, 0.050 and 0.075 mol%) are prepared by solid-state reaction. Pellets sintered at 1070 °C for 12 h are characterised by X-ray diffraction, scanning electron microscopy/energy dispersive spectroscopy and impedance spectroscopy. Current density-electric field, dielectric loss and permittivity measurements are also carried out. Rietveld refinement showed the substitution of Cr(III) on the Ti(IV) site, with the maximum substitution for x = 0.025 mol%. The generation of electrical defects in the grain boundary region by chromium doping is responsible for increasing the electric breakdown field strength and nonlinearity coefficient at room temperature from 1723 V/cm and 5.29 for x = 0 mol% to 3431 V/cm and 8.16 for x = 0.025 mol%. This composition shows the greatest improvement in ceramic varistor parameters.
Orginal Article
 Select Comparisons of corrosion behaviour for X65 and low Cr steels in high pressure CO2-saturated brine Yong Hua, Sikiru Mohammed, Richard Barker, Anne Neville J. Mater. Sci. Technol., 2020, 41 (0): 21-32.  DOI: 10.1016/j.jmst.2019.08.050 Appropriate materials for injection pipelines and tubing for carbon dioxide geologic storage is fundamental to ensure asset integrity and save cost. This paper evaluates the corrosion behaviour of X65, 1Cr, 3Cr and 5Cr, which have the potential to be injection pipeline/tubing materials. The influence of steel Cr content on the general and localised corrosion behaviour was investigated at time periods from 6 to 192 h at 60 °C and 100 bar. The evolution, morphology and chemistry of corrosion products on the surface of each material were evaluated using a combination of scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction and related to their overall corrosion protection. Results indicate that prior to the formation of protective films on the steel surfaces, the resistance of the materials to corrosion increase with increasing Cr content (Corrosion resistance: X65 < 1Cr<3Cr<5Cr). However, as corrosion products evolve, the protection afforded to the different steels significantly varies and decreases with increasing Cr content. × 65 becomes the material with the lowest general corrosion rate by the end of the 192 h experiments and 5Cr exhibits the highest corrosion rate (ranking of corrosion resistance: X65 > 1Cr>3Cr>5Cr). In terms of the corrosion products on X65, both inner amorphous and outer crystalline corrosion layers consist of FeCO3. For the Cr-containing steels, the outer layer also comprises FeCO3, but the inner layer is enriched with Cr, and is predominantly amorphous Cr(OH)3. The extent of localised corrosion (determined using surface profilometry) is noticeably less for X65 compared to the Cr-containing steels. The paper raises questions about the benefits that low Cr steels offer towards extending component design life compared to carbon steel under the test conditions considered here.
Research Article
 Select Corrosion resistance of self-cleaning silane/polypropylene composite coatings on magnesium alloy AZ31 Zhao-Qi Zhang, Rong-Chang Zeng, Cun-Guo Lin, Li Wang, Xiao-Bo Chen, Dong-Chu Chen J. Mater. Sci. Technol., 2020, 41 (0): 43-55.  DOI: 10.1016/j.jmst.2019.08.056 Magnesium (Mg) and its alloys have been widely used in a variety of industrial fields, however, the high corrosion rate and surface contamination restrict their applications. In this study, a corrosion-resistant polymer coating with self-cleaning properties on Mg alloy AZ31 was successfully fabricated via a pretreatment of amino-silane (poly(3-aminopropyl)trimethoxysilane, PAPTMS) and subsequently covered with a polypropylene (PP) film. Surface morphology and chemical compositions were examined using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and Fourier transform infrared spectrophotometry (FT-IR) and X-ray photoelectron spectroscopy (XPS) as well. Contact angle was measured to determine hydrophobicity of the composite coatings. Water permeability of the coatings was evaluated through electrochemical impedance spectroscopy (EIS). Corrosion resistance of the coating was investigated using electrochemical and hydrogen evolution tests. Results indicated that PAPTMS/PP coatings possessed a micrometer-scaled porous spherical microstructure, and super-hydrophobicity with high water contact angle (162 ± 3.4°) and low sliding angle (5 ± 0.6°) due to the low surface energy (10.38 mJ/m2). Moreover, the coating exhibited a smaller water diffusion coefficient (8.12 × 10-10 cm2/s) and water uptake volume fraction (24.5 %), demonstrating low water permeability and good physical barrier performance. As a result, the corrosion current density of PAPTMS/PP coating exhibited approximately three orders of magnitude lower than that of the AZ31 substrate, suggesting excellent corrosion resistance. Finally, corrosion-resistant mechanism of the hybrid coating was proposed.
 Select In vitro insights into the role of copper ions released from selective laser melted CoCrW-xCu alloys in the potential attenuation of inflammation and osteoclastogenesis Yanjin Lu, Xiongcheng Xu, Chunguang Yang, Ling Ren, Kai Luo, Ke Yang, Jinxin Lin J. Mater. Sci. Technol., 2020, 41 (0): 56-67.  DOI: 10.1016/j.jmst.2019.09.016 In this study, the CoCrW-xCu alloys (x = 2, 3 and 4 wt%) were fabricated using selective laser melting (abbreviated as Co-2Cu, Co-3Cu and Co-4Cu) with the purpose of reducing the inflammation responses and the activity of osteoclast. The metal ions releasing test showed that when the Cu content was less than 4 wt%, the releasing amount of Co and Cr ions was very small; however, when 4 wt% Cu was added in the CoCrW based alloy, the quantity of Co ions was significantly elevated with respect to the other groups due to the segregation of precipitates in the matrix; the Cu2+ ion quantity of the Co-2Cu, Co-3Cu and Co-4Cu alloys were 0.05, 0.09 and 0.27 μg/(L cm2) after 7 d immersion, respectively; the RT-qPCR and ELISA data indicated that the expression levels of the pro-inflammatory cytokines (TNF-α and IL-6) were down-regulated in the Co-3Cu and Co-4Cu groups, whereas the expression level of the anti-inflammatory cytokine (IL-10) was up-regulated in all CoCrW-xCu alloys; meanwhile, the Cu-containing CoCrW alloys significantly down-regulated the expression of the NF-κB signal pathway in a Cu content-dependent manner, and the downstream transcription factors of NF-κB signal pathway including NFATc1, TRAP and Cath-K were also down-regulated via potentially manipulating the NF-κB signal pathway. After comprehensive consideration, it is considered that the Co-3Cu alloy is a potential material for self-alleviating inflammatory responses.
 Select A novel graphene aerogel synthesized from cellulose with high performance for removing MB in water Jin Li, Qin Wang, Lei Zheng, Hongbo Liu J. Mater. Sci. Technol., 2020, 41 (0): 68-75.  DOI: 10.1016/j.jmst.2019.09.019 A novel graphene aerogel has been synthesized from cellulose by an easy way through sol-gel reaction and carbonization. In this route, it can be found the products have a high yield about 48 % and form a specific porous networks assembled by graphene flake. The product sample like CGA-2, characteristic of a specific area about 1426.11 m2/g and total pore volume about 1.02 cm3/g, exhibits a remarkable performance for removing cationic dye like methylene blue (MB) in water. Of which the maximal MB adsorption capacity can be found about 610.85 mg/g in a neutral solution and 1.2 g/g in a basic solution. Under the condition of initial MB concentration of 100 mg/L and pH of 7.0, the adsorption equilibrium can be achieved on CGA-2 in 10 min, with MB removal ratio about 99 %. In the MB adsorption on CGA-2, the isotherm fits Langmuir model with correlation coefficient of 0.9905, and the kinetics follows pseudo-second-order model with correlation coefficient of 0.9999.
Letter
 Select Effects of temperature and alloying content on the phase transformation and {10$\bar{1}$1} twinning in Zr during rolling Xinglong An, Hao Zhang, Song Ni, Xiaoqin Ou, Xiaozhou Liao, Min Song J. Mater. Sci. Technol., 2020, 41 (0): 76-80.  DOI: 10.1016/j.jmst.2019.09.022 The effects of temperature and Ti content on the deformation mechanisms of pure Zr and Zr-Ti alloys were investigated by transmission electron microscopy. The results indicate the existence of a relation between deformation-induced phase transformation from a hexagonal close-packed structure to a face-centered cubic structure and {10$\bar{1}$1} deformation twinning. That is, when one is suppressed, the other will be promoted. The phase transformation was suppressed while the {10$\bar{1}$1} compressive twinning was promoted with increasing the rolling temperature and/or Ti content. This can be attributed to the activation of basal dislocations at high temperature and the increased stacking fault energy with Ti content.
Research Article
 Select Tuning magnetic properties, thermal stability and microstructure of NdFeB magnets with diffusing Pr-Zn films Jiajie Li, Xiangyun Huang, Liangliang Zeng, Bo Ouyang, Xiaoqiang Yu, Munan Yang, Bin Yang, Rawat Rajdeep Singh, Zhenchen Zhong J. Mater. Sci. Technol., 2020, 41 (0): 81-87.  DOI: 10.1016/j.jmst.2019.09.024 Grain boundary diffusion process (GBDP) serves as a promising approach in improving magnetic properties and thermal stability of NdFeB permanent magnets. Herein, non-heavy rare earth Pr-Zn films deposited on the magnet surface using DC-magnetron sputtering system are reported. The thermal stability and coercivity enhancement mechanism of Pr-Zn GBDP magnets were investigated. Results show that the coercivity of Pr-Zn GBDP magnet increases from 963.96 kA m-1 to 1317.14 kA m-1 without any remanence reduction. Notably, the demagnetization curve of Pr-Zn GBDP magnet still remains a high squareness ratio. The temperature coefficient of coercivity and anti-demagnetization ability of Pr-Zn GBDP magnet under high temperatures are improved after GBDP treatment. The well-optimized rare earth-rich (RE-rich) grain boundary phases and high effective anisotropy field of (Nd,RE)2Fe14B magnetic hardening layers surrounding main grains are the key factors to impact the magnetic properties and thermal stability of NdFeB permanent magnets via GBDP treatment.
 Select Synthesis of unique-morphological hollow microspheres of MoS2@montmorillonite nanosheets for the enhancement of photocatalytic activity and cycle stability Peng Chen, Shilin Zeng, Yunliang Zhao, Shichang Kang, Tingting Zhang, Shaoxian Song J. Mater. Sci. Technol., 2020, 41 (0): 88-97.  DOI: 10.1016/j.jmst.2019.09.021 In this work, MoS2@montmorillonite nanosheets hollow microspheres (MoS2@MMTNS-HMS) with a novel morphology structure was successfully synthesized through loading MoS2 to the surface of MMTNS-HMS via hydrothermal method. The novel material has been characterized through the measurements of SEM, TEM, Raman spectra and UV-vis absorption spectra. The results have shown that MoS2@MMTNS-HMS emerges higher light-utilization efficiency, density of edge active sites and separation of photoelectrons, owing to its unique hollow structure, vertically-aligned MoS2 nanosheets, which greatly enhances its photocatalytic activity. Furthermore, the cycle stability of MoS2@MMTNS-HMS is much higher than that of pristine MoS2, which is attributed to that MMTNS-HMS greatly inhibits the oxidation of MoS2 during photocatalytic. MoS2@MMTNS-HMS could be a promising photocatalyst for the applications in the elimination of organic pollutants.
 Select On the texture memory effect of a cross-rolled Mg-2Zn-2Gd plate after unidirectional rolling Pengfei Zhang, Yunchang Xin, Ling Zhang, Shiwei Pan, Qing Liu J. Mater. Sci. Technol., 2020, 41 (0): 98-104.  DOI: 10.1016/j.jmst.2019.05.076 A Mg-2Zn-2Gd alloy subjected to a cross rolling and annealing often has a texture with c-axes of grains evenly distributing on a circle approximately 40° away from the normal direction (ND), which can completely remove the planar mechanical anisotropy. The texture memory effect and planar mechanical anisotropy of such a cross-rolled plate after an unidirectional rolling and subsequent annealing were systematically investigated. The results show that the circle-shaped texture is partially retained after the unidirectional rolling and annealing, with basal poles evenly distributing on an ellipse approximately 30°-40° away from the ND. This small texture difference will lead to quite different mechanical anisotropies between the two plates, namely, a quite low anisotropy of yield strength between the rolling direction (RD) and transverse direction (TD) before the unidirectional rolling, in contrast to an obvious mechanical anisotropy after unidirectional rolling. A quantitative calculation shows that tension along the RD of the plate after the unidirectional rolling will activate a much higher fraction of prismatic slip than tension along the TD. The much higher critical resolved shear stress for prismatic slip than that for basal slip or {10 $\bar{1}$ 2} twinning accounts for the much higher yield strength of TD tension than that of RD tension. The mechanisms for texture evolution during the unidirectional rolling and annealing were also discussed.
 Select Microstructure and mechanical properties of double-side friction stir welded 6082Al ultra-thick plates C. Yang, J.F. Zhang, G.N. Ma, L.H. Wu, X.M. Zhang, G.Z. He, P. Xue, D.R. Ni, B.L. Xiao, K.S. Wang, Z.Y. Ma J. Mater. Sci. Technol., 2020, 41 (0): 105-116.  DOI: 10.1016/j.jmst.2019.10.005 In the present work, 80 mm thick 6082Al alloy plates were successfully double-side welded by friction stir welding (FSW). The relationship between the microstructures and mechanical properties was built for the double-side FSW butt joint with more attention paid to the local characteristic zones. It was shown that a phenomenon of microstructural inhomogeneity existed in the nugget zone (NZ) through the thickness direction. The grain size presented an obvious gradient distribution from the top to the bottom for each single-pass weld, and the microhardness values decreased from both surfaces to the middle of the NZ. The lowest hardness zone (LHZ) exhibited a “hyperbolical”-shaped distribution extending to the middle of the NZ. Similar tensile properties were obtained in the three sliced specimens of the FSW joint, and the joint coefficient reached about 70% which achieved the same level as the conventional FSW Al alloy joints. Finite element modeling proved that the “hyperbolical”-shaped heat affected zone (HAZ) was beneficial to resisting the strain concentration in the middle layer specimen which helped to increase the tensile strength. Based on the analysis of the hardness contour map, tensile property and microstructural evolution of the joints, an Isothermal Softening Layer (ISL) model was proposed and established, which may have a helpful guidance for the optimization on the FSW of ultra-thick Al alloy plates.
 Select Sulfur-doped g-C3N4/rGO porous nanosheets for highly efficient photocatalytic degradation of refractory contaminants Yanmei Zheng, Yuanyuan Liu, Xinli Guo, Zhongtao Chen, Weijie Zhang, Yixuan Wang, Xuan Tang, Yao Zhang, Yuhong Zhao J. Mater. Sci. Technol., 2020, 41 (0): 117-126.  DOI: 10.1016/j.jmst.2019.09.018 Graphitic carbon nitride (g-C3N4, CN) has attracted increasing interests in the field of photocatalysis due to its high visible-light-response. However, its photocatalytic activity is still lower for degradation of refractory contaminants such as Cr(VI) and Rhodamine B (RhB) etc. Herein, we report a facile method to synthesize a novel sulfur(S)-doped CN/reduced graphene oxide (rGO) porous nanosheet (S-CN/rGO PNs) via a supramolecular self-assembling followed by a solvothermal treatment. The as-prepared porous S-CN/rGO PNs are stable with high specific surface area ～188.5 m2g-1 and exhibit a significantly enhanced photocatalytic activity of ～17-fold and 15-fold higher than that of bulk CN for the degradation of RhB and Cr(VI) under visible light irradiation, respectively. Typically, 50 mL of 15 mg/mL RhB can be degraded within 20 min by 10 mg S-CN/rGO PNs. The mechanism can be explained by the synergistic effect of S doping and porous structure which can effectively reduce the band gap of CN and increase the specific surface area to promote the separation and transfer of photo-generated charge carriers. The results have provided a new way to significantly enhance the photocatalytic activity of g-C3N4 for degradation of refractory contaminants.
 Select Structures and formation mechanisms of dislocation-induced precipitates in relation to the age-hardening responses of Al-Mg-Si alloys Y.X. Lai, W. Fan, M.J. Yin, C.L. Wu, J.H. Chen J. Mater. Sci. Technol., 2020, 41 (0): 127-138.  DOI: 10.1016/j.jmst.2019.11.001 In the slightly deformed Al-Mg-Si alloys, dislocation-induced precipitates are frequently observed, and they usually line up, forming sophisticated precipitation microstructures. Using atomic-resolution electron microscopy in association with hardness measurements, we systematically investigated these precipitates in relation to the age-hardening responses of the alloys. Our study reveals that the majority of dislocation-induced complex precipitates are actually short-range ordered while long-range disordered polycrystalline precipitates and multiphase composite precipitates, including polycrystalline U2 precipitates, B'/U2, B'-2/U2, B'/B'-2/U2 and β'/U2 composite precipitates. It is suggested that the formation of these complex precipitates is mainly owing to a high nucleation rate and rapid growth of different precipitate phases parallel to the associated dislocation lines. Since dislocation-induced precipitates consume more Mg than Si from the matrix and have a high formation kinetics, they will have different impacts on the matrix precipitation in different types of Al-Mg-Si alloys. Our results further demonstrate that for the “normally-β"-hardened” alloy, their formation leads to a coarser precipitate microstructure in the matrix, whereas for the “normally-β'-hardened” alloy, their formation reverses the precipitation pathway in the matrix, resulting in a reduced age-hardening potential of the former alloy and an improved age-hardening potential of the latter alloy.
 Select Simultaneously enhanced strength and ductility of 6xxx Al alloys via manipulating meso-scale and nano-scale structures guided with phase equilibrium Qiang Lu, Kai Li, Haonan Chen, Mingjun Yang, Xinyue Lan, Tong Yang, Shuhong Liu, Min Song, Lingfei Cao, Yong Du J. Mater. Sci. Technol., 2020, 41 (0): 139-148.  DOI: 10.1016/j.jmst.2019.09.029 Excellent comprehensive mechanical properties including good formability, high strength and high ductility are prior demands for Al-Mg-Si-Cu alloys. This study utilizes calculation of phase diagram (CALPHAD) to simplify the alloy design and meet these demands. Specifically, CALPHAD was used to finely tune the Mg/Si atomic ratio in solid solution and accurately control the type and content of second phases, especially to avoid the formation of the harmful constituent phase β-AlFeSi. Constituents and dispersoids of only α-AlFeMnSi phase were found in the alloy prepared. An optimized microstructure with fine grains, micro scale constituents, densely distributed submicron scale dispersoids and extremely dense nano precipitates provides effective impediment to dislocation gliding and induces transgranular fracture. Therefore, the designed alloy has better comprehensive mechanical properties than other 6xxx series aluminum alloys, including excellent formability, strength and ductility. The low T4P strength of 149 MPa as well as the high elongation of 26.1% implies the alloy's applicability to automobile body panel forming. The yield strength was rapidly improved from 149 MPa to 277 MPa during the paint bake ageing, because the number density of precipitates is twice as high as that of some other 6xxx alloys. Meanwhile, the elongation was kept at a high level of 20.0%.
 Select Precipitation mechanism and microstructural evolution of Al2O3/ZrO2(CeO2) solid solution powders consolidated by spark plasma sintering Wanjun Yu, Yongting Zheng, Yongdong Yu J. Mater. Sci. Technol., 2020, 41 (0): 149-158.  DOI: 10.1016/j.jmst.2019.09.028 It is difficult to synthesize Al2O3/ZrO2 solid solution because of its low solubility under equilibrium solidification conditions. In this work, a new combustion synthesis combined with water atomization (CS-WA) method was developed to prepare supersaturated Al2O3/ZrO2(CeO2) solid solution powders. The ultra-high cooling rate supplied by CS-WA greatly extends solid solubility of Al2O3 in ZrO2. The precipitation mechanism of solid solution was investigated by systematic heat treatments. The initial temperature of the metastable phase decomposed into Al2O3 and ZrO2 is 1050 °C, and it could be completely precipitated at 1400 °C in 0.5 h. The precipitated ZrO2 particles were uniformly dispersed in Al2O3 matrix and grew into submicron scale at annealing temperature of 1450 °C. Subsequently, together with detailed microstructure, phase composition, as well as mechanical properties were collaboratively outlined to discuss spark plasma sintering (SPS) behavior. The solid solution precipitated Al2O3 matrix and ZrO2 particles during the SPS process. Partial ZrO2 particles were uniformly distributed within Al2O3 matrix, while the residuary ZrO2 located at the grain boundaries and formed special transgranular/intergranular structure. The average size of nanoscale transgranular ZrO2 particles was only ～11.5 nm. The compact ZrO2 toughened Al2O3 nano ceramic (N-ZTA) exhibits excellent mechanical properties. This work provides a guidance to produce nanostructured ZTA with high performance.
 Select Preparation of sulfur hydrophobized plasmonic photocatalyst towards durable superhydrophobic coating material Emese Lantos, László Mérai, Ágota Deák, Juan Gómez-Pérez, Dániel Sebők, Imre Dékány, Zoltán Kónya, László Janovák J. Mater. Sci. Technol., 2020, 41 (0): 159-167.  DOI: 10.1016/j.jmst.2019.04.046 The widely used photocatalytic self-cleaning coating materials are often made of polymers and polymer based composites, where the photocatalyst immobilization occurs with macromolecules. However, these organic polymers are often unstable under exposure to UV irradiation and easily degraded by reactive radicals produced in the photocatalytic reaction. In order to solve this problem, in this paper, we present the facile preparation of a multifunctional coating with dual superhydrophobic and photocatalytic properties, where the fixation and the hydrophobization of the plasmonic Ag-TiO2 photocatalyst particles with visible light activity was performed with non-water soluble sulfur, which is a cheap and easily available material. The resulted novel nanocomposite with rough and nano-tructured surface roughness (1.25-2.45 nm determined by small-angle X-ray scattering) has sufficient low surface energy (3.3 mJ/m2) for superhydrophobic (θ = 151.1°) properties. Moreover, in contrast of the organic and expensive fluoropolymer based composites, this non-wetting nature was durable, because the measured θ was higher than 150° during the long- term LED (λmax = 405 nm) light irradiation.
 Select Ultrafast synthesis of gold nanoparticles on cellulose nanocrystals via microwave irradiation and their dyes-degradation catalytic activity Madhusudhan Alle, Seung-Hwan Lee, Jin-Chul Kim J. Mater. Sci. Technol., 2020, 41 (0): 168-177.  DOI: 10.1016/j.jmst.2019.11.003 This study represents a well-dispersed gold nanoparticles (AuNPs) synthesis process via cellulose nanocrystals (CNC) which acts as both reducing and supporting agent. The synthesis process was ultrafast and completed in a few seconds using microwave irradiation. The entire synthesis process was cost-effective, sustainable and eco-friendly. The synthesized (AuNPs/CNC) nanocomposite was investigated by transmission electron microscopy, selected area electron diffraction, Fourier transform infrared spectroscopy, energy dispersive X-ray analysis, X-ray diffraction, and UV-vis spectroscopy. The obtained AuNPs were well accumulated on the CNC surface and had a uniform spherical shape with an average diameter of 8 ± 5.3 nm. The diameter of AuNPs could be altered by tuning the concentration of CNC suspension. The synthesized AuNPs/CNC nanocomposite film exhibited excellent degradation properties against various organic dyes, namely, Allura red, Congo red, Rhodamine B and Amaranth. The ultrafast degradation reactions followed pseudo first order kinetics. In the catalytic degradation reaction, AuNPs/CNC was transmitting electrons from a donor (NaBH4) to an acceptor (a dye).
 Select Microstructure and mechanical properties of Al-Mg-Si alloy fabricated by a short process based on sub-rapid solidification Ze-Tian Liu, Bing-Yu Wang, Cheng Wang, Min Zha, Guo-Jun Liu, Zhi-Zheng Yang, Jin-Guo Wang, Jie-Hua Li, Hui-Yuan Wang J. Mater. Sci. Technol., 2020, 41 (0): 178-186.  DOI: 10.1016/j.jmst.2019.08.053 Al-Mg-Si (AA6xxx) series alloys have been used widely in automotive industry for lightweight purpose. This work focuses on developing a short process for manufacturing Al-0.5Mg-1.3Si (wt.%) alloy sheets with good mechanical properties. Hereinto, a preparation route without homogenization was proposed on the basis of sub-rapid solidification (SRS) technique. The sample under SRS has fine microstructure and higher average partition coefficients of solute atoms, leading to weaker microsegregation owing to the higher cooling rate (160 °C/s) than conventional solidification (CS, 30 °C/s). Besides, Mg atoms tend to be trapped in Al matrix under SRS, inducing suppression of Mg2Si, and promoting generation of AlFeSi phase. After being solution heat treated (T4 state), samples following the SRS route have lower yield strength compared with that by CS route, indicating better formability in SRS sample. After undergoing pre-strain and artificial aging (T6 state), the SRS samples have comparable yield strength to CS samples, satisfying the service requirements. This work provides technological support to industrially manufacture high performance AA6xxx series alloys with competitive advantage by a novel, short and low-cost process, and open a door for the further development of twin-roll casting based on SRS technique in industries.
 Select Wetting behaviors of molten melt drops on polycrystalline Al2O3 substrates in high magnetic fields Tie Liu, Yubao Xiao, Zhengyang Lu, Noriyuki Hirota, Guojian Li, Shuang Yuan, Qiang Wang J. Mater. Sci. Technol., 2020, 41 (0): 187-190.  DOI: 10.1016/j.jmst.2019.08.037 We measured the contact angles of Al and Sn drops on polycrystalline Al2O3 substrates in various high magnetic fields at different temperatures. The contact angles of both Al and Sn drops on the Al2O3 substrates decreased under high magnetic fields. These decreases strongly depend on the temperature, magnetic flux density, magnetic properties of the metal drops, and the reactivity of the metal drops with Al2O3. Our results reveal that the wetting behavior of molten metal drops on ceramics can be modified by a high magnetic field.
 Select Microstructure, wear resistance, and corrosion performance of Ti35Zr28Nb alloy fabricated by powder metallurgy for orthopedic applications Wei Xu, Xin Lu, Jingjing Tian, Chao Huang, Miao Chen, Yu Yan, Luning Wang, Xuanhui Qu, Cuie Wen J. Mater. Sci. Technol., 2020, 41 (0): 191-198.  DOI: 10.1016/j.jmst.2019.08.041 A ternary Ti35Zr28Nb alloy was fabricated by powder metallurgy (PM) from pre-alloyed powder. The microstructure, hardness, corrosion behavior, and wear response of the produced alloy were investigated systematically. The results show that nearly full dense Ti35Zr28Nb alloy (relative density is 98.1 ± 1.2 %) can be fabricated by PM. The microstructure was dominated with uniform β phase. The Ti35Zr28Nb alloy displayed spontaneous passivity in a naturally aerated simulated body fluid (SBF) solution at 37 ± 0.5 °C. The Ti35Zr28Nb alloy exhibited the highest corrosion resistance as compared to as-cast Ti6Al4V and pure Ti because of the formation of a protective passive film containing TiO2, Nb2O5, and ZrO2, including the highest corrosion potential (-0.22 ± 0.01 V), the lowest corrosion current density (57.45 ± 1.88 nA), the lowest passive potential (0.05 ± 0.01 V) and the widest passivation range (1.29 ± 0.09 V). Under the same wear condition, the wear rate of the Ti35Zr28Nb alloy (0.0021 ± 0.0002 mm3/m·N) was lower than that of the CP Ti (0.0029 ± 0.0004 mm3/m·N) and close to that of the Ti6Al4V (0.0020 ± 0.0003 mm3/m·N). The wear mechanism of the Ti35Zr28Nb alloy was mainly dominated by abrasive wear, accompanied by adhesive wear. The highest corrosion resistance together with the adequate wear resistance makes the PM-fabricated Ti35Zr28Nb alloy an attractive candidate for orthopedic implant materials.
 Select Comparative study of performance comparison of AlSi10Mg alloy prepared by selective laser melting and casting Qian Yan, Bo Song, Yusheng Shi J. Mater. Sci. Technol., 2020, 41 (0): 199-208.  DOI: 10.1016/j.jmst.2019.08.049 The influence of the microstructure on mechanical properties of AlSi10Mg fabricated by casting and selective laser melting (SLM) were investigated and contrasted in this work, with an emphasis on understanding the forming mechanism. The microstructure, phase structure and mechanical properties were characterized by scanning electron microscopy/field-emission Transmission Electron Microscopy (SEM/TEM), X-Ray Diffraction (XRD), tensile and fatigue tests. The results indicated that the SLM AlSi10Mg exhibited a supersaturated Si network structure precipitated along α-Al cell. Brittle β-Al5FeSi and π-Al8FeMg3Si6 phases were found in the as-cast and SLM AlSi10Mg respectively due to different thermal histories during processing. The SLM AlSi10Mg showed higher tensile strength but lower elongation than the casting, as the result of grain refinement and tortuous crack path. The fatigue results revealed that unmelted powder, oxide inclusion and pores can considerably degrade the fatigue properties for the SLM AlSi10Mg. The SLM process offered a new method for material processing that would avoid harmful Fe-bearing intermetallic compounds and refine the microstructures for enhancing strength.
 Select On the origin of the high tensile strength and ductility of additively manufactured 316L stainless steel: Multiscale investigation Bassem Barkia, Pascal Aubry, Paul Haghi-Ashtiani, Thierry Auger, Lionel Gosmain, Frédéric Schuster, Hicham Maskrot J. Mater. Sci. Technol., 2020, 41 (0): 209-218.  DOI: 10.1016/j.jmst.2019.09.017 We report that 316L austenitic stainless steel fabricated by direct laser deposition (DLD), an additive manufacturing (AM) process, have a higher yield strength than that of conventional 316L while keeping high ductility. More interestingly, no clear anisotropy in tensile properties was observed between the building and the scanning direction of the 3D printed steel. Metallographic examination of the as-built parts shows a heterogeneous solidification cellular microstructure. Transmission electron microscopy observations coupled with Energy Dispersive X-ray Spectrometry (EDS) reveal the presence of chemical micro-segregation correlated with high dislocation density at cell boundaries as well as the in-situ formation of well-dispersed oxides and transition-metal-rich precipitates. The hierarchical heterogeneous microstructure in the AM parts induces excellent strength of the 316L stainless steel while the low staking fault energy of the as-built 316L promotes the occurrence of abundant deformation twinning, in the origin of the high ductility of the AM steel. Without additional post-process treatments, the AM 316L proves that it can be used as a structural material or component for repair in mechanical construction.
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