Invention of high performance magnesium alloys with trade-off balancing by multi-scale controlling

本研究的目的是通过从电子或原子水平到宏观水平的多尺度控制来平衡高性能镁合金。结果总结如下。(1)在“基于第一性原理分子动力学计算的变形行为分析与合金设计”中，从理论计算各单晶理想滑移变形广义层错能的结果出发，讨论了导致镁合金脆性的基本滑移面和棱柱滑移面的临界分解剪应力差异较大的问题。结果发现，添加Li、Al或Zn可以使差异很小。此外，从电子密度分布的角度讨论了键合强度的各向异性。(2)在“具有优异力学性能和成形性的合金的材料工艺建设”中，等径角挤压（ECAE）法制备的Mg-Zn系合金的细小锆析出相均匀分布和晶粒细化，使合金的冲击性能得到改善。此外，在ECAE处理的Mg-AI系合金（AZ31）中，通过晶粒细化和织构控制，发现了应变率与伸长率的反向关系，在室温下，当冲击应变率为1.8 x 10^3 s^<-1>时，伸长率的提高不低于50%。此外，还清楚地表明，在各种合金中都可以发现低温或高应变速率的超塑性。(3)在“扩散结合与搅拌摩擦焊接技术的建立”中，从压缩超塑性变形中的空腔消失模型中导出了描述扩散结合条件的方程，表明在最优条件下，AZ31合金的结合强度只需铝结合时间的三分之一即可达到足够的结合强度。此外，虽然纯镁在搅拌摩擦焊中无法获得足够的结合强度，但合金的结合强度达到母材的90%以上。(4)在“从轧制薄板出发的压力机制造技术的建立”中，发现成形极限取决于凸肩上拉伸弯曲的断裂极限，在473 K或更低的温度下加热可以提高成形极限。结果表明，难以用拉伸试验评价的局部变形性能对获得良好的冲压成形具有重要意义，并提出了用缺口试件弯曲试验评价成形性的新方法。少

This research purpose is the invention of the high performance magnesium alloys, which are trade-off balanced by multi-scale controlling from electron or atomic level to macroscopic level. The results are summarizes to below.(1)In "the analysis for deformation behavior and an alloy design by the first principle molecular dynamics calculation", the big difference in the critical resolved shear stress between basal and prismatic slip planes, which leads to the brittle-nature of magnesium, was discussed from the results by theoretical calculation on the generalized stacking fault energy in ideal slip deformation of each single crystal. As the result it was found that an addition of Li, Al or Zn could make the difference small. Moreover, the anisotropy of the bonding strength was discussed from the electron density distribution.(2)In "the construction of the materials process for the alloy having an excellent in mechanical property and formability", an improvement in the impact properties … More was attained by the uniform distribution in fine Zr-precipitates and the grain refinement on the Mg-Zn system alloy processed by equal-channel-angular-extrusion (ECAE). Moreover, the strain-rate reverse dependency of the elongation was found in the ECAE processed Mg-AI system alloy (AZ31) by the achievement of grain refinement and texture control, and improvement in no less than 50% elongation was attained under an impact strain-rate of 1.8 x 10^3 s^<-1> at room temperature. Moreover, it was shown clearly that low temperature or high-strain-rate superplasticity could be discovered in various alloys.(3)In "the establishment of the diffusion bonding and the friction stir welding technology", the equation describes the diffusion bonding condition was drawn from the cavity-disappearance model in the compressive superplastic deformation, and it was shown that the bonding strength of AZ31 alloy sufficient in one third of the bonding time of aluminum under an optimal condition could be obtained. Moreover, although, as for pure magnesium, sufficient bonding strength was not obtained in friction stir welding, with the alloy, 90% or more of the bonding strength of mother material was obtained.(4)In "the establishment of the press fabrication technology from rolling sheets", it was found that the forming limit depended on the fracture limit of the tensile bending on the punch shoulder, and it improved by heating at 473 K or less. Moreover, it was shown that the local deformability, which was hard to evaluate by the tensile test, was important to obtain the good press fabrication, and the new method to evaluate the formability by a notched-specimen bending test was proposed. Less