Magnesium - Science, Technology and Applications

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Authors: Y.Q. Ma, Rong Shi Chen, En Hou Han
Abstract: A new steel mold gravity casting magnesium alloy of low-cost, high strength, and high ductility has been developed and studied. This new magnesium alloy, which is designated as IMR-41, exhibits high strength (Yield Tensile Strength≈145 MPa, Ultimate Tensile Strength≈280 MPa) and high ductility (Elongation≈8%) at room temperature. The alloying elements are inexpensive ones and the cost of IMR-41 is similar to AZ91 series. The influence of small X element addition and heat treatment on the microstructures and mechanical properties are discussed. The IMR-41 combines the virtues of AZ91 series and AM60 series to some extend and shows great potential application on wheels of lightweight vehicles or motorcycles, etc. which require high strength and high ductility simultaneously.
Authors: Wei Neng Tang, Rong Shi Chen, En Hou Han
Abstract: The variation of the flow stress and the microstructural evolution during hot deformation at different test temperatures and strain-rates are studied. During hot deformation, dynamical recrystallization did not occur completely; after annealing at 523K, microstructural changes due to static recrystallization and small grain sizes of several micrometers and fine nanometer-precipitates can be attained. The stress exponent (n) and the activation energy (Q) for high temperature deformation have been evaluated and the deformation mechanisms at different temperature have also been discussed.
Authors: Rong Shi Chen, Jean Jacques Blandin, Michel Suéry, En Hou Han
Abstract: Mechanical properties and microstructure of extruded AZ91(-Ca) alloys have been studied in this paper. The results showed that Ca has no significant effect on reducing grain size of the extruded AZ91 alloy. The ambient temperature tensile tests showed that the ultimate and yield strength of extruded AZ91 alloy decreased by addition of Ca. At elevated temperature, Ca addition improves the yield strength of both AZ91 alloy. The variations in microstructure and mechanical properties of the AZ91 alloy are also discussed in terms of the effects of Ca on grain refinement and formation of constituent phases.
Authors: Hai Feng Liu, Guodong Tong, Jun Hou
Abstract: A series of high temperature creep resistant magnesium alloys for die casting based on AZ91 were successfully developed by the addition of Rare Earth, and Calcium. The original target of magnesium alloy development was aimed at cylinder head cover of high power diesel engine, and tried to satisfy the temperature demands of gear-box house. The tensile property at room temperature, creep behavior at 150ı,and analysis of microstructure were discussed in this paper. The results showed that these alloys has potential for die casting to produce power-train parts, and greatly decrease the weigh of parts.
Authors: Hai Ping Cao
Abstract: Some commercial Mg components have been die cast at various casting conditions. The influence of process parameter settings on the microstructural features as well as one kind of defect called segregation band defect were investigated. It was found that more pre-solidified crystals were formed in the condition of lower casting temperature, and more broken dendrites and spherical crystals were formed under higher injection speed. The distribution characters of pre-solidified crystals were also presented and discussed in this paper. Concerning the band defects formed during die casting, a variety of segregation band morphologies as well as the influence of various casting conditions the performances on bands was presented. It was found out that intensification pressure has the strongest effect on the performance of segregation bands inside the castings.
Authors: Tadayoshi Tsukeda, Ken Saito, Mayumi Suzuki, Junichi Koike, Kouichi Maruyama
Abstract: We compared the newly developed heat resistant magnesium alloy with conventional ones by Thixomolding® and aluminum alloy by die casting. Tensile properties at elevated temperatures of AXEJ6310 were equal to those of ADC12. In particular, elongation tendency of AXEJ6310 at higher temperature was better than those of the other alloys. Creep resistance of AXEJ6310 was larger than that of AE42 by almost 3 orders and smaller than that of ADC12 by almost 2 orders of magnitude. Fatigue limits at room temperature and 423K of AXEJ6310 was superior among conventional magnesium alloys.
Authors: Hong Liang Zhao, Shao Kang Guan, Chun Xiang Zhang, Fei Yan Zheng, Li Guo Wang, Qing Kui Li
Abstract: Better properties of magnesium make it a natural choice for use as an anode material in rechargeable batteries. However, the magnesium alloy thin sheets used in rechargeable batteries were produced by ingot casting and rolling. That technology was so complex and the cost was high. Rapidly solidification by melt spinning is an effect way to solve that problem. In this paper, the technology of rapidly solidified (RS) ribbons in Mg-3%Al-1%Zn-0.2%Mn alloy has been investigated using melt spinning technique. The effect of wheel speed on thickness and microhardness of the ribbons is presented. Microhardness is found to increase with the wheel speed. Rapidly solidification leads to small grains (1~2 µm). The plasticity of the ribbons was well. The quantity of Mg17Al12 decreases with the increase in wheel speed. When the wheel speed reaches 1600 rpm, no Mg17Al12 phase precipitates. As the increase of the wheel speed, the corrosion resistance of the ribbons changes better.
Authors: Chun Mei Yang, Ding Fei Zhang, Pei Dao Ding, Jian Peng, Xu Hong Chen
Abstract: In this paper, the influence of the cooling rate on the solidified structure of ZK60 Mg alloy has been studied by means of Gleeble-1500D thermal simulation instrument. The result showed that the grain size and grain shape depended on the cooling rate, Primary Dendrite Arm Space ( λI ) and Secondary Dendrite Arm Space ( λII) sharply decreased with the increasing of solidifying cooling rate (v) in the range of experimental cooling rate (0.2~100K/s). When superheat was constant, the empirical formulas of the relation between λI λII and v was obtained. In addition, the dependence between micro-hardness (HV) and Secondary Dendrite Arm Space ( λII) for ZK60 casting alloy was proved to be similar with Hall-Petch formula. The empirical formula for λII-HV has been proposed.
Authors: L. Lu, Arne K. Dahle, John A. Taylor, David H. StJohn
Abstract: The fundamentals of grain refinement are reviewed with particular focus on magnesium alloys. This is followed by considerations of the theoretical and practical aspects of grain refinement of Mg-Al alloys by carbon-based grain refiners. Finally, experimental results using Al4C3 as a potential grain refiner are presented and discussed.
Authors: Qi Chi Le, J. Cui, Kenong Xia
Abstract: Several Mg alloys were processed to achieve the thixotropic microstructure of non-dendritic, globular primary grains for semisolid forming using a novel method that does not require stirring. The alloys were poured at their liquidus temperatures or about ten degrees below the liquidus temperatures using either batch or semi-continuous casting. Although the compositions of the alloys had considerable effects on details of the resulting microstructure, generally fine, equiaxed primary grains were obtained by controlling the resting time, casting speed and cooling rate. The lower casting temperatures and addition of calcium were effective in preventing burning of Mg without using a protective atmosphere. This new method has great potential for industry applications.

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