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Authors: Sang Min Lee, K. Ryu, Young Jae Kwon, J.G. Kim, Won Seung Cho, Nam Hee Cho, Chin Myung Whang, Yeon Chul Yoo
437
Authors: Joong Hwan Jun, Jeong Min Kim, Ki Duk Seong, Ki Tae Kim, Woon Jae Jung
Abstract: Changes in tensile properties of A206 Al-Cu-Mg casting alloys containing trace amount of rare earth(RE) elements up to 0.2% were investigated and discussed in relation to the microstructural evolution. The A206 alloy with 0.1%RE shows higher values of ultimate tensile strength(UTS) and yield strength(YS) than A206 alloy at room and elevated temperatures up to 300oC, whereas no remarkable change is found in elongation with respect to RE addition. In view of X-ray diffractometry(XRD) and transmission electron microscopy(TEM), the improvement of tensile strength in the A206 alloy with 0.1%RE would be caused by higher number density of Al2Cu(q¢) strengthening precipitates.
441
Authors: Ze Kun Yao, Xinmin Liang, Hong Zhen Guo, Bin Wang, Guo Hui Li, Zh. Qiao, Hui Zhang
Abstract: It has been investigated that the influence of processing parameters on mechanical properties of weld zone for Ti-24Al-15Nb-1.5Mo and TC4 dual alloy welded by electron beam in vacuum. The results shows the remarkable influence factors are heat treatment regime and deformation for yield strength of welded dual alloy samples at room temperature tensile test, and the remarkable influence factor is forging temperature for the elongation in tensile test at 500°C. From the combined analysis about other properties at room temperature and 500°C, the microstructure of the weld seam, it can been gotten the optimum parameters of processing dual alloy, i.e. forging at 1020°C, soaking for 12 hour at 700°C, air cooling, about 40% deformation and using billet of rolling state.
445
Authors: D.S. Sekhawat, M. Chakraborty, U.K. Chatterjee
Abstract: In-situ Al-TiB2 metal matrix composites containing 5 wt% and 10 wt% TiB2 have been synthesized through master alloy and mixed salt routes. The composites have shown five times increase in wear resistance compared to commercially pure aluminium. Corrosion evaluation by polarization technique carried out in NaCl, H2SO4 and NaOH solutions indicates a lower corrosion resistance of the composites than the corresponding base metals. The composites produced through mixed salt route suffered higher corrosion than those prepared by master alloy route. The results have been explained from the physical and electrochemical effects of TiB2 in the matrix.
449
Authors: Katsuyoshi Kondoh, Ritsuko Tsuzuki, Wenbo Du, Shigeharu Kamado
Abstract: Materials and processing designs for advanced magnesium alloys with fine microstructures and superior properties were established by the combination of the repeated plastic working and the Mg2Si synthesis in solid-state. The grain size was less than 1 μm via RPW process due to its severe plastic working on raw powder. The hot extruded magnesium alloys produced in industries showed high ultimate tensile strength, e.g. 420~450MPa, when employing Mg-Zn-Al-Ca-RE (Rare Earth) alloy coarse powder, having 0.5~2 mm diameter, as input materials.
453
Authors: Sung S. Park, Young Min Kim, Dae H. Kang, Nack J. Kim
Abstract: AZ31 and experimental ZMA611 alloys were strip cast into 2 mm thick strips. The as-cast AZ31 alloy strip consists of columnar dendrites. On the other hand, as-cast ZMA611 alloy strip shows equiaxed dendritic structure through the thickness of strip. These alloys were subjected to various thermomechanical treatments and their tensile properties were evaluated. Strip cast AZ31 alloy in H24 condition has equivalent yield and tensile strengths with similar ductility compared to commercial ingot cast AZ31-H24 alloy, indicating that strip casting is a viable process for the fabrication of Mg alloy strips. The ZMA611 alloy has a large volume fraction of fine dispersoid particles in the microstructure, resulting from the beneficial effect of strip casting on microstructural refinement. It has been shown that the ZMA611 alloy has superior tensile properties compared to commercial ingot cast AZ31-H24 alloy, suggesting the possibility of the development of new wrought Mg alloy sheets by strip casting.
457
Authors: Ming Zhou, Nai Yi Li, Henry Hu
Abstract: High pressure die cast magnesium alloy AM50 is currently used extensively in complex shaped automotive components with various cross-section thicknesses. Understanding of the effect of section thicknesses on mechanical behavior of AM50 is critical for proper design of different applications. In the present study, magnesium alloy AM50 was high pressure die cast into rectangular coupons with section thicknesses of 2, 6 and 10 mm. The prepared coupons were tensile tested at room temperature. Microstructure analysis and porosity measurement were performed on the representative specimens. The results of tensile testing show that the tensile properties including yield strength (YS), ultimate tensile strength (UTS) and elongation(Ef) decreases with an increase in section thicknesses of die cast AM50. Microstructure and porosity analyses indicate that the observed tensile behavior of die cast AM50 is primarily attributed to the level of porosity which resulted from entrapped gases during the high pressure die casting process.
463
Authors: Ming Yi Zheng, Xiao Guang Qiao, Shi Wei Xu, Kun Wu, Shigeharu Kamado, Yo Kojima
Abstract: Equal channel angular extrusion (ECAE) was performed on as-cast ZW1101 (Mg-11wt%Zn- 0.9wt%Y) Mg alloy containing quasicrystallines. The grain size of α-Mg was effectively refined, and coarse eutectic quasicrystalline phases were broken and dispersed in the alloy by ECAE. The alloy processed by ECAE exhibited a good combination of high strength and high ductility, which is due to the grain refinement and fine dispersed quasicrystallines in the alloy.
469
Authors: Ming-Xu Xia, Hong-xing Zheng, Sen Yuan, Jian Guo Li
Abstract: The phase and morphological transformation during the remelting process was investigated by isothermal soaking and rapidly quenching of preformed AZ91D magnesium alloys in semisolid state. It was revealed that the morphological transformation of preformed alloys is crucial to obtain homogenously fine spheroidal grains and affect the final forming ability. The transformation is divided into two stages, local remelting of the whole experiment and partial remelting of the respective grains, which behave as liquid bands and liquid cells structures, respectively. In the partial melting, the lower melting point phase, β-Mg17Al12, diffused to the grains boundary and center of the grains and separated to Al2Mg and Mg. The Al2Mg and Mg phases with lower melting points melt into cells structures. The final microstructure of the remelting experiments is composed of cells structures, spheroidal grains and liquid phase.
473
Authors: Xi Yan Zhang, Feng Jiang, Shi-jie Zhou, Chong Jia, Min Zhao, Xue Qin Li
Abstract: Some Zn and a little Ag are added into ZM5 magnesium alloy (one of Mg-9 wt%Al-1 wt%Zn alloys in China), and the differences of the microstructures and properties between the new alloy and ZM5 is investigated. Effects of heat treatment and alloying elements (Zn and Ag) on the microstructure and tensile properties of Mg-9Al-xZn alloys, and relationships between the chemical composition, microstructure and properties are investigated. Zn ad Ag have obvious solid solution strengthening effects on Mg-9Al-xZn alloy, while Ag is detrimental to the corrosion resistance after being artificial aged. The morphology of pearlite-like secondary γ(Mg17Al12) phase (γII) has close relation with the properties.
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