Papers by Author: Wen Jiang Ding

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Authors: Yi-wen Zeng, Li Ming Peng, Xie Min Mao, Xiao Qing Zeng, Wen Jiang Ding
Abstract: Sulphur hexafluoride (SF6) is widely used by the magnesium industry as a protective atmosphere. It has been demonstrated that SF6 prevents molten magnesium from further oxidation by reacting with magnesium to make the surface film on the magnesium melt denser. However, due to its high greenhouse effect (GWP=23900), the alternatives of SF6 must be sought. In this paper, 1,1-difluoroethane (commercially named HFC-152a), whose GWP value is only 140 and far lower than that of SF6, was tested to check its capacity of ignition-proof and further-oxidation-proof. Similar to SF6, the melt’s surface film formed in the protective atmosphere containing HFC-152a has a shiny metallic appearance. The surface film’s microstructure has been characterized with X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD’s results showed that the film contains only MgO and MgF2 phases while SEM showed their morphologies are uniform.
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Authors: Zhong Shan Wei, Liufa Liu, Wen Jiang Ding
Abstract: Aluminum arc spray process was employed to form an aluminum coating on AZ31 magnesium alloy substrate. Anti-corrosion property of the Al-coated specimens was evaluated by salt immersion tests and electrochemical tests. There was no apparent inter-layer diffusion or compound layer formation between the aluminum coating and the substrate under as-sprayed condition. To improve the density of the coating and the bonding strength between the coating and the substrate, a heat treatment process was conducted after spraying to form an interlayer by metallurgic diffusion. The interlayer consisted of large primary crystal Mg17Al12 phase and minute lamella structure that consisted of Mg17Al12 and α-Mg. The hardness of both the aluminum coating and the interlayer are higher than that of the substrate. In electrochemical experiments, the corrosion current density decreased from 2.4×10-1mA/cm2 of AZ31 to 7.1×10-3mA/cm2 of heat-treated specimen. It suggests that the corrosion resistance of AZ31 can be greatly improved by aluminum arc spray with a following heat treatment process.
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Authors: Xing Wu Guo, Jian Wei Chang, Shang Ming He, Peng Huai Fu, Wen Jiang Ding
Abstract: The corrosion behavior of GW63 (Mg-6wt.%Gd-3wt.%Y-0.4wt.%Zr) alloys in 5% NaCl aqueous solution has been investigated by PARSTAT 2273 instrument. The Open Circuit Potential (ECORR) vs. time curve, cyclic polarization (Pitting Scans) curve and Electrochemical Impedance Spectroscopy (EIS) was measured for the GW63 alloys in as-cast and T6 heat treatment conditions. The EIS results indicated that the tendency of impedance variation for as-cast condition was monotonic decreasing, however, the tendency of variation for T6 condition was not completely monotonic but the total tendency was decreasing. The values of impedance of GW63 alloy at 0.1 Hz are about 103 ohm-cm2 for as-cast and T6 condition.
571
Authors: Ying Xin Wang, Xiao Qin Zeng, Wen Jiang Ding, Alan A. Luo, Anil K. Sachdev
Abstract: Uniaxial hot compression tests were performed at constant temperature (T) and strain rate (ε& ) in the ranges of 200-500 °C at an interval of 50 °C and 0.001-20 s-1. The flow stress data were used to develop the extrusion limit diagram for AZ31 and AM30 magnesium tubes. The extrusion limit diagram shows a wide region available for extruding AZ31 and AM30 seamless tubes, and comparison of the two extrusion limit diagrams shows that, the extrudability of AM30 alloy is better than that of AZ31 alloy. Actual extrusion trials validated the predicted temperature rise limit curve corresponding to the occurrence of surface cracking during the extrusion process. Magnesium tubes were successfully extruded according to the safe regions identified by the extrusion limit diagram.
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Authors: Guang Yin Yuan, Man Ping Liu, Wen Jiang Ding, Akihisa Inoue
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Authors: Wen Jiang Ding, Guo Hua Wu, Bong Sun You, Dong Yim Chang
Abstract: The effects of CeCl3-containing fluxes on RE element loss, the high temperature mechanical properties, microstructure and corrosion properties of magnesium alloy containing RE have been studied. The results showed that a certain amount of CeCl3 in purification fluxes restrained the reaction between the Ce element and fluxes to decrease the loss of Ce in alloys. With the flux containing 9% CeCl3, the loss rate of alloy element Ce can be reduced from 26.9% to 3.4%, and the σb and δ of the alloys at 150°C counld be improved from 160.9MPa and 6.2% to 176.5MPa and 7.9% compared with that of conventional MgCl2-containing flux , respectively. Besides, the coarse β phase and rod-like RE phase were refined effectively by CeCl3-containing fluxes.
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Authors: Jin Bao Lin, Qu Dong Wang, Li Ming Peng, Yang Zhou, Wen Jiang Ding
Abstract: Microstructure and mechanical properties of Mg-6.0wt%Zn-0.5wt%Zr (ZK60) alloy were studied as a function of cooling rate. The temperature field and cooling rate during the casting process were investigated by use of finite element analysis (FEA) simulation. The results showed that the microstructure was refined and the eutectic phase distributed much uniformly with the increase of cooling rate. The increase of yield strength, ultimate strength and elongation can be ascribed to the strengthening effect of fine grain. Relationship between grain size and yield strength is consistent with the Hall-Petch formalism: 1/ 2 80.37 132.56 − = + d y σ .
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Authors: Jian Wei Chang, Peng Huai Fu, Xing Wu Guo, Li Ming Peng, Wen Jiang Ding
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Authors: Guo Hua Wu, Hong Tao Guo, Xiao Qing Zeng, Wen Jiang Ding
Abstract: By use of the Zwick electronic universal material testing machine, X-ray diffractometer, SEM, EDX, image analyzer and corrosion test, the effects of LaCl3 on the mechanical properties, structure, fractography and corrosion behavior of magnesium alloy have been studied. The results show that minute nodular Al10La2Mn7 phases can be formed in Mg melts after fluxes containing LaCl3 are added to Mg melt. The Al10La2Mn7 phases can act as the nucleating site of γ phases, and the γ phases can be refined. With the flux containing 5% LaCl3, the σb and δ of the Mg alloy can be improved from 161MPa and 2.1% to 203MPa and 4.0% by 26% and 100%, respectively. The corrosion rate of magnesium alloys can decrease from 1.10 mg/(cm2.d) to 0.17 mg/(cm2.d) by 84% with the use of flux containing 5% LaCl3. Rare earth (RE) elements are often added to the magnesium alloy to improve the alloy structure and the room or elevated temperature mechanical properties. But up to present, the RE elements added to Mg melt is often in the form of pure RE alloy or RE master alloy [1]. Because RE is the oxidizable material, this kind of adding process often leads to low RE utilization ratio and high use-cost. Besides, this process can easily induce segregation of RE and the appeared coarse RE phases will lower the Mg alloy mechanical properties. By far, there is few research reports about RE contained compound added to Mg alloy melt. In this paper, the effects of Lanthanum chloride (LaCl3) on the structure and mechanical properties of Mg alloy are studied for the first time. The aim is to explore a new way to improve the Mg alloy properties.
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Authors: Qiang Li, Qu Dong Wang, Da Quan Li, Wen Jiang Ding
Abstract: The effect of Nd and Y addition on the microstructure and mechanical properties of as-extruded Mg-Zn-Zr magnesium alloy has been investigated in this study. The Mg-Zn-Zr alloy had 11 μm average grain size due to dynamic recrystallization during hot extrusion; but the average grain sizes of the Mg-Zn-Nd-Y-Zr alloys were markedly reduced to 4 μm by Nd and Y additions. The lamellar α-Mg + T phase or α-Mg + W phase eutectics at grain boundaries in as-cast Mg-Zn-Nd-Y-Zr alloys were broken up and MgZn2 precipitates in the matrix are obtained during hot extrusions. The mechanical properties of as-extruded Mg-Zn-Zr alloy were improved significantly by Nd and Y additions, especially the elevated temperature strength, which was above 150 MPa in ultimate tensile strength at 250 °C. These may be ascribed to the very fine grain size, the dispersed T phase or W phase and the MgZn2 type Laves phase precipitating during hot extrusion.
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