Magnesium - Science, Technology and Applications

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Authors: Xuefeng Guo, Jacob Kinstler, Lilia Glazman, Dan Shechtman
Abstract: Based on the commercial alloy ZK60 which contains 6%Zn, high strength Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6%Zr magnesium alloy bars of 10 to 50 mm in diameters were prepared by rapid solidification (RS) and extrusion processes (RSE). For those RSE solid bars, the ultimate tensile strengths steadily maintain on a level of 490 to 520 MPa, the elongations are between 6 to 10%. The HV50 hardness is between 85 and 90. In order to reveal materials microstructures both RS ribbons and RSE solid bars, the Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6%Zr alloy was analyzed with an optical microscopy (OM), a scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS) and an X-ray diffraction apparatus. It was found that the microstructure of the RS ribbon consists of super saturated (Mg) solid solution; thermally stable Mg3Y2Zn3 (W) and Mg7Ce2 intermetallic compound particles which uniformly dispersed interior grains and W and Mg7Ce2 compound networks at grain boundaries. After extrusion, the microstructure of RSE Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6%Zr solid bar consists of the same phases as the RS ribbons. The networks existing at RS ribbon’s grain boundaries were break up into submicron particles and dispersed uniformly on the matrix formed after extrusion.
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Authors: Klaus Siegert, Stephan Jäger, Mihai Vulcan, C. Wizemann
Abstract: This paper deals with pneumatic bulging of Magnesium AZ31 sheet metal and AZ31 tubes at elevated temperatures. Flow-stress curves determined by tensile tests and pneumatic bulging at different forming temperatures and strain rates are presented for magnesium AZ31 sheet metal. It is shown that based on basic investigations an automotive sheet-metal component can be formed at elevated temperatures. To determine the material properties of magnesium tubes, tensile tests have been conducted at different forming temperatures and constant strain rate. It is shown how a forming process followed by a heat treatment process influences the microstructure and the formability of magnesium AZ31 tubes.
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Authors: G.I. Rosen, G. Segal, A. Lubinsky
Abstract: The aim of this project is to develop magnesium alloys extrusion technology for large profiles for application in the automotive industry. In particular it is expected to significantly reduce chassis weight, thus leading to fuel consumption reduction and enhancement of performance of the cars produced by the end user. The entire process required for magnesium alloys extrusion of automobile chassis will be addressed as a first attempt of large magnesium profile extrusion. The challenge of large magnesium profile extrusion (outer diameter up to 10") has never been addressed due to technological barriers that relate to limited capability of magnesium extrusion technology. However, these barriers can be overcome if one has control over the starting material. Since the final performance of the finished product depends on the original microstructure formed over Direct Chill (DC) casting, homogenization, extrusion and subsequent heat treatment, no processing step can be isolated from the other. The R&D activities will focus on alloy selection, production of large magnesium billets, die design, heat treatment and extrusion parameters. These will be accompanied by an economic assessment of the new technology and additional applications.
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Authors: Tsutomu Murai, Hajime Oguri, Shin-ichi Matsuoka
Abstract: Effects of manganese contents in AZ31 and AZ10 on billets microstructure, extrusion loads, occurring of surface cracks and mechanical properties were investigated. In the range 0 to 0.8% manganese content, there exist an adequate manganese content for avoiding surface cracks and obtaining the highest tensile strength.
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Authors: Qiang Wang, Bao Cheng Li, Zai-xin Feng
Abstract: Aimed at characteristics of the profile such as complex shape, high dimensional accuracy and mechanical properties, the reduction zone length and devided flow taper of female die were designed by FEM and extrusion experiments were carried out for as-cast AZ31 magnesium alloy. Technological parameters were determined and microstructure and properties of the extruded profile were examined. The results show that magnesium alloy profile can be extruded if technological parameters such as deformation temperature, tool temperature and ratio of extrusion are controlled strictly. Each of the above mentioned technological parameters has its different influence on microstructure and properties of extruded profile. In comparison with as-cast alloys, microstructure is refined from 120~140μm to about 10μm and tensile strength is enhanced from 171~200MPa to above 260Mpa. This suggests that fine grain and high strength are attained for AZ31 magnesium alloy by extrusion deformation. The extruded profile can meet high properties demands for carrying parts. It provides a possibility for broader usage of magnesium alloy profiles.
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Authors: Qin Luo, Qing Dong, Zuyuan Yang
Abstract: The process of the safety design process, the structure principle and the key technology are described. The technology of dual molder, gas-water combined condensation, online fire fighting and infrared thermo-induction automatic disconnecting relief valve is used in this machine, which , compared to the current domestic “erect-pit output” technology, enjoys higher security & reliability during the production, higher effiiciency and better stability of the products. It perfectly meets the demand of the “horizontal output” process.
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Authors: Xing Zhang, Bao Cheng Li, Zhi Min Zhang, Zhi Wen Wang
Abstract: Split Hopkinson Pressure Bars (SHPB) was applied to investigate shock resistance of magnesium alloy. The deformation behaviour was reported of ZK60 magnesium alloy at high strain rate, and the relationship was established between the dynamic properties and the impact velocity. Results indicate: with impact velocity improvement, much twinned crystal and fine grain can be obtianed, this made dynamic properties enhancement of ZK60 alloy.
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Authors: X.L. Wang, Yong Ning Yu, Erde Wang
Abstract: It is well known that the ductility of magnesium and magnesium alloy is too poor to be processed. After normal hot extrusion, the ductility of magnesium alloy will be improved, but not noticeably. In this paper, further extrusion (Extrusion Ratio is 6.25) is adopted to commercial AZ31 magnesium alloy rods (Extrusion Ratio is 2) at different temperatures in order to refine the size of grain, then the rods with the crystallite size between 4-10μm is obtained, and the influence of crystallite with different grain size on the ductility of this alloy is investigated further. A lot of experiments and research indicate that: the elongation of the initial billet with the grain size of 30μ m can reach about 12%; after extrusion at different temperatures, the grain size can be refined to below 10μm, and the ductility goes up to 24%-30%. It also shows that, when the grain size of AZ31 magnesium alloy is below 10μm, the ductility is effected obviously. Only when the grain size is about a few microns, the ductility of AZ31 magnesium alloy will be improved noticeably.
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Authors: Zhi Min Zhang, Qiang Wang, Bao Hong Zhang
Abstract: In order to study the warm forming strengthening behaviours of AZ31 magnesium alloy, plane strain compression tests were carried out at the temperatures ranged from 210 to 330°C for as-cast and pre-forged Alloys. Tensile specimens were machined from the compressed samples. Room temperature mechanical testing was conducted according to the specifications. Microstrutres were investigated using scanning electron microscope. The analysis revealed that there is an excellent warm forming strengthening effect for as-cast AZ31 alloy with hexagonal close-packed structure. The increments of the tensible strength is about 40~50%. With decreasing temperature, the tensible strength increases during warm forming. The deformation extent and deformation mode has its different influence on strengthening effect. The high strength was attributed to the fine-grain strengthening and work hardening. This suggests that fine grain and high strength are attained for AZ31 alloy by means of rational combined action of work hardening and fine-grain strengthening during warm forming.
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