Papers by Author: Jing Zhang

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Authors: Ming Bo Yang, Fu Sheng Pan, Jing Zhang, Jin Zhang
Abstract: The current status of research and application in the AZ(Mg-Al-Zn), AS(Mg-Al-Si), AE(Mg-Al-RE), AX(Mg-Al-Ca), ACM or MRI(Mg-Al-Ca-RE)and AJ(Mg-Al-Sr)series elevated temperature magnesium alloys are reviewed, will special attention paid to the effects of alloying elements and the control of second phases. The existing problems on the development of elevated temperature magnesium alloys are discussed.
Authors: Jing Zhang, Fu Sheng Pan, Z. Xiao Guo
Abstract: The practical phase constituent diagram has been used to determine the composition of a low alloying τ-type Mg-Zn-Al alloy, which has a nominal element content of 7wt%Zn and 3wt%Al (ZA73), as a basis for further improvement of τ-type alloy through appropriate thermal processing and micro-alloying. The microstructure and solidification characteristics of the alloy have been experimentally examined using optical microscopy, scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry analysis. The results confirm that the as-microstructure of ZA73 alloy consists of globular equiaxed dendrite with τ phase as the only secondary phase evenly distributed in interdendritic spacing. Solidification sequence has been proposed with the help of DSC analysis and Mg-Zn-Al ternary liquidus projection phase diagram. Consistent with previous observed results for τ-type Mg-Zn-Al alloy, due to the decrease of element contents, ZA73 alloy has higher liquidus temperature (~627°C) and wider solidification range (~283°C), while at the mean time lower starting temperature of the second phase transformation (~354°C), compared to higher element containing ZA104 alloy. The phase constituent diagram has been shown to be a practical and effective tool for predicting the as-cast microstructural constituent of high zinc Mg-Zn-Al alloys under normal permanent mould solidification condition.
Authors: Yan Long Ma, Ru Lin Zuo, Ai Tao Tang, Wen Ming Wang, Jing Zhang, Fu Sheng Pan
Abstract: Morphologies of precipitation phases along grain boundaries of the as-cast Mg-6.0Zn-0.45Zr, Mg-6.0Zn-1.2Y and Mg-6.0Zn-0.6Zr-1.0Y alloys were investigated. The experimental results indicated that the main precipitation phase along grain boundary of the as-cast Mg-6.0Zn-0.45Zr was a Mg-Zn binary compound. There were two kinds of precipitation phases along grain boundaries for Mg-6.0Zn-1.2Y and Mg-6.0Zn-0.6Zr-1.0Y alloys. One grew at triangular grain boundary, which was fish-bone -like in shape and a Mg-Zn binary compound. The other distributed mainly around the grain, which was net-like in shape and a Mg-Zn-Y ternary compound. In addition, there were lots of granular phases, extending to the interior of the grain, at the rim of grain boundary phases. Y was found to affect obviously morphology of precipitation phases along grain boundary of the as-cast Mg-Zn-Zr (ZK60) alloys.
Authors: Fu Sheng Pan, Jian Peng, Ai Tao Tang, Jing Zhang, Qing Liu, Z. Xiao Guo
Authors: Fu Sheng Pan, Kui Li, Ai Tao Tang, Yu Wang, Jing Zhang, Z. Xiao Guo
Authors: Fu Sheng Pan, Wen Ming Wang, Yan Long Ma, Ru Lin Zuo, Ai Tao Tang, Jing Zhang
Abstract: Alloy phases in the as-aged (T6) ZK60 magnesium alloy were investigated. More attentions were paid to types and morphologies of main alloy phases in the as-aged ZK60 magnesium alloy. The experimental results indicated that there was an abundant flower-shaped segregation in the solution-treated ZK60 magnesium alloy. A small quantity of undissolved compounds, MgZn2, was also found. They distributed irregularly in the form of similar parallelogram, with a dimension of 200nm~500nm and not sensitive to heat-treatment. Mg2Zn3 was found to be a main secondary compound in the as-aged ZK60 alloy, which precipitated during aging. Another precipitation phase, MgZn, in the as-aged ZK60 magnesium alloy was also found in the form of long and thin rods with a dimension of 500nm.
Authors: Jing Zhang, Wei Yan, Chen Guang Bai, Xiao Dong Luo, Fu Sheng Pan
Abstract: Hydrogen storage in solid hydrides is the most attractive method of on-board hydrogen storage in fuel cell for cars. Mg metal exhibits a high-storage capacity by weight and has been considered a group of potentially attractive candidates for solid-state hydrogen storage. In this study, mechanochemical synthesis of nanocrystalline Mg-based hydrogen storage composites from various starting materials in specialized hydrogen ball mills has been achieved. The reactive synthesis process and the hydrogen desorption behaviors of the composite hydrides were investigated by X-ray diffraction (XRD), thermogravimetric and differential scanning calorimetry (TG-DSC). The results show that nano-sized MgH2 and Mg(AlH4)2 could be directly synthesized by pure Mg and pretreated Al powder, as well as Mg-Li-Al alloy powder. Alloying element Li could remarkably promote the synthesis of magnesium alanate, the product composite hydrides releasing 6.2wt% H2 through multi-step decompositions, of which the starting endothermic peaks are as low as 65°C.
Authors: Xiao Dong Luo, Jing Zhang, Hao Liu
Abstract: Magnesium hydride is considered as one of the most interesting alternatives for the reversible storage of hydrogen. In this study,The feasibility and reaction process of different materials(Mg and pretreated Al powders(mainly composed of Al and Ni))were discussed and investigated by thermodynamic calculation. The effects of material proportioning, mill time, mill energy density were also investigated by XRD analysis and TG-DSC technique, and analyzed the essence mechanism. The results show that nano-sized MgH2 and Mg(AlH4)2 could be directly synthesized by pure Mg and pretreated Al powder, The product composite hydrides release 2.7wt% H2 through multi-step decompositions, of which the starting endothermic peaks are as low as 265°C.
Authors: Jing Zhang, Xu Feng Zhang, Fu Sheng Pan, Chuan Pu Liu, Qu Bo He
Abstract: The microstructures, mechanical properties, and formability of an Mg-1.5Zn-0.1Zr alloy with rare earth element of Erbium addition have been examined by using optical microscopy, scanning electron microscopy/energy dispersive X-ray spectroscopy, and thermal mechanical testing. The results showed that Erbium combined with Mg and impurity elements forming small particles dispersed on the matrix. Therm-mechanical simulation in the temperature range from 250°C to 400°C and strain rate from 0.1 to 1.0 indicated that the flow stress decreases with the increase of the temperature and the decrease of the strain rate. Sheet samples were prepared through ingot casting, hot rolling, cold rolling, and intermediate annealing. Remarkable grain size refinement was realized through recrystallization during the rolling process. Good combination of strength and ductility was achieved by applying intermediate annealing before the very last cold rolling. Further improvement of ductility and formability could be obtained by conducting proper heat treatment on the finishing cold-rolled sheets.
Authors: Jing Zhang, Qi Ma, Fu Sheng Pan, Ru Lin Zuo
Abstract: The effects of rare earth addtition of Er on the microstructures and mechanical properties of Mg-9Zn-Zr magnesium alloys were examined. The results showed that the addition of Er resulted in the formation of two types of thermally stable Er-bearing compounds with distinct Zn/Er ratio. The volume fraction of the second-phase particles increased with the increase of Er addition. 2% Er could refine the as-cast microstructure effectively. The yield strength generally increased and the elongation decreased gradually. 0.5% Er-bearing alloy had optimum combined mechanical properties, with the yield strength, tensile strength and elongation being 313MPa, 366MPa and 22%, respectively. Furthermore, addition of Er brought about homogenous deformation behaviour and recrystallization behaviour to the alloy.
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