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Authors: Mark Easton, Chris H.J. Davies, Matthew R. Barnett, Franka Pravdic
Abstract: A recent trial investigated the effect of solidification grain refinement of billet on the grain refinement and properties of alloy ZM20. It was found that even at levels of 0.4Mn, significant grain refinement could be obtained when 0.7Zr was added. At 0.2Mn grain sizes as low as 60μm were obtained. Billets of Mg-2Zn-0.2Mn with four different grain sizes, due to different Zr and cooling rates were then cast via vertical direct chill casting and extruded conventionally. Benefits of grain refinement of the billet on extrusion were found to be a slight increase in the size of the operating window, and a reduction of the grain size in the extrudate. However, the effect of the reduction in extrudate grain size due to refinement of the billet was small compared with the amount of grain refinement obtained due to recrystallisation on extrusion.
Authors: Xin Jin Cao, Min Xiao, Mohammad Jahazi, Tasneem Shariff
Abstract: The feasibility of laser repair was studied based on single-/two-layer multi-bead cladding using a continuous wave (CW) 4 kW Nd:YAG laser system and 1.6-mm EZ33A-T5 filler rods for 22.5-mm ZE41A-T5 magnesium alloy sand castings in the machined surface conditions. The results demonstrate the potentiality of repairing magnesium castings using laser surface cladding by wire. Similarly to weld joints, three distinct regions, i.e. clad, partially melted and heat affected zones are observed in the laser-clad beads. The microstructures in these zones and their evolutions are discussed in details.
Authors: Dirk Steglich, Stéphane Graff, Wolfgang Brocks
Abstract: A crystal plasticity model has been used to simulate channel die experiments on both, pure magnesium single crystals and polycrystalline textured rolled plates. Deformation mechanisms and slip system activity can be identified by FE-analyses of single crystals. The role of twinning can be understood and modeled phenomenologically by an additional slip system. Simulations of polycrystalline aggregates are used to obtain a representation of the material's phenomenological yield function in order to describe the plastic deformation behavior using the framework of continuum mechanics. This allows for accounting for the specific texture and thus for its optimization. The tension- compression asymmetry, which is typical for mechanically processed magnesium material, can be reproduced by means of the crystal plasticity and a phenomenological model.
Authors: Kunio Matsuzaki, Kanichi Hatsukano, Y. Torisaka, Kotaro Hanada, Toru Shimizu, M. Kato
Abstract: Mg-Al-Zn alloys containing 0.5% Ca were strip cast into sheets with a thickness of about 1.0mm by twin roll caster. It is found that the addition of Ca to Mg95Al5-XZnX (wt%)alloys prevents the oxidation and burning of molten, and makes the melting and casting easy. The as-cast Mg96Al4Zn0.5Ca0.5 alloy sheet has few cracks at the edge. With increasing Zn content, the generation of cracks occurs more markedly. The as-cast alloys have equiaxed grains with an average grain size of 10 μm. A fine microstructure is obtained. All the samples consist of single hcp-Mg phase. The yield and ultimate tensile strength of the as-cast sheets are in the range of 180 to 200 MPa and 265 to 275 MPa, respectively. The alloy Mg95Al2Zn2.5Ca0.5 shows an elongation of 21% as well as a high strength of 275 MPa. The annealing at 400 °C causes an improvement of elongation to 24% and 30% for Mg96Al4Zn0.5Ca0.5 and Mg95Al2Zn2.5Ca0.5,respectively. A further enhancement of mechanical properties is expected by an appropriate thermomechanical treatment. The as-cast Mg96Al4Zn0.5Ca0.5 sheet was deep drawn at 250°C and a drawing ratio of 2.0 without cracking . In summery, the Ca added Mg alloys are suitable for the production of Mg alloy sheets by strip casting and the cast alloy sheet have high strength with ductility and good formability
Authors: Shi Hong Zhang, Zhang Gang Li, Yong Chao Xu, Li Mei Ren, Zhong Tang Wang, Li Xin Zhou
Abstract: Press forging of magnesium alloy AZ31 sheets was investigated in this paper. The typical component, a rectangular box with bosses at the bottom was formed. The experimental results show that the magnesium alloy sheets are suitable for press forging. The bosses and the rectangular box can be formed synchronously for 2 mm or 3 mm thick sheets when the punch temperature is 250 °C. By experimentation and numerical simulation, the effects of process parameters on material flow were analyzed, including the temperature, the die shape, the blank size, the lubrication manners and the friction condition.
Authors: Xin Sheng Huang, Kazutaka Suzuki, Yong Jai Kwon, Akira Watazu, Ichinori Shigematsu, Naobumi Saito
Abstract: A differential speed rolling (DSR) processing with a roll speed ratio of 1.167 was carried out on an AZ31 alloy for investigating the effects of DSR on microstructure, texture and mechanical properties. The DSR processed sheet showed unidirectional shear bands with a small grain size of 5.5 μm inclining to the rolling direction, and the basal plane tended to incline at about 15º from the rolling plane toward the rolling direction. Compared with the normal rolled sheet, the DSR processed sheets showed a lower proof stress and a larger elongation with an increase from 21% to 26% in the rolling direction. The proof stress increased and the elongation decreased with the angle between the tensile direction and the rolling direction.
Authors: Joong Hwan Jun, Ki Duk Seong, Jeong Min Kim, Ki Tae Kim, Woon Jae Jung
Abstract: The Effects of Li content and annealing treatment on microstructure and damping capacity for Mg-X%Li alloys have been investigated, based on experimental results from X-ray diffractometry (XRD), optical microscopy (OM), hardness tests and vibration damping tests in a flexural mode. The Mg-X%Li alloys containing Li of 3%, 8% and 13% consist of α (HCP) single phase, (α + β (BCC)) dual phases and β single phase, respectively. In as-rolled state, the damping capacity for Mg-Li alloys shows a similar level regardless of Li content. The annealing treatments at 200oC and 400οC give rise to an enhancement of damping capacity only for the Mg-3%Li and Mg-8%Li alloys containing α phase, and at the same annealing temperature, the Mg-3%Li alloy with fully α structure exhibits higher damping capacity. This result indicates that the damping capacity of Mg-Li alloys depends principally on α phase, and that the annealing treatment is necessary to improve its damping capacity.
Authors: Tokimasa Kawabata, Yuya Fukuda, Kenji Matsuda, Shigeharu Kamado, Yo Kojima, Susumu Ikeno
Abstract: The high resolution transmission electron microscope (HRTEM) observation was carried out to investigate the microstructure of precipitates in Mg-Gd-Y-Zr alloy. In the early stage of aging at 423K, monoatomic layers were observed along the (1 1 00)Mg plane. After 64h aging at 423K, the contrast of β” phase based on ordered D019 hexagonal super lattice structure was appeared. The monoatomic layers, two layers spaced by (1 1 00) Mg planes and β’ phase based on bco-structure were observed in the specimen aged for 128h. In the peak- aged specimen, the β’ phase and monoatomic layers were observed.
Authors: Jeong Min Kim, Jae Min Lee, Joong Hwan Jun, Ki Tae Kim, Woon Jae Jung
Abstract: A small amount of Zn or Sn was added to Mg-3%Al alloy to improve the formability of alloy. The elongation of as-rolled alloy was increased at both room temperature and 300oC by addition of Sn or Zn, even though the tensile strength at room temperature was remarkably increased only by Zn. When the as-rolled alloy was annealed to be fully recrystallized, the ductility at room temperature was significantly enhanced, however the elongation at 300oC was rather decreased probably attributed to the dynamic recrystallization occurred during the tensile test.
Authors: Jae Seol Lee, Hyeon Taek Son, Ik Hyun Oh, Jae Ik Cho, Chang Seog Kang, Jung Chan Bae
Abstract: The aims of this study ares to investigate the microstructure evolution of AZ31 Mg alloys with normal rolling and cross rolling during the large strain hot rolling affects microstructure, texture and mechanical properties of AZ31 Mg alloy. In the microstructures of as-rolled both samples, twins are clearly apparent, small and recrystallized grains are visible along some grain boundary and twinned regions. The lankford values of large strain cross rolled sample obviously demostrate the higher average r-value and lower planar anisotropy value. The press formaility of large strain rolled Mg alloy might be improved due to control of texture and grain size by change of the rolling direction.

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