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

本研究的目的是发明高性能镁合金，通过从电子或原子水平到宏观水平的多尺度控制来权衡权衡。主要研究结果如下：(1)在《变形行为分析与合金设计的第一性原理分子动力学计算》中，通过对各单晶理想滑移变形时广义层错能的理论计算结果，讨论了导致镁合金脆性的基面和棱面滑移面临界分辨剪应力的巨大差异。结果发现，添加Li、Al或Zn可以使这种差异变小。此外，还从电子密度分布的角度讨论了粘结强度的各向异性。(2)在具有优异力学性能和成形性能的合金的材料工艺的构建中，改善了…的冲击性能采用等通道转角挤压(ECAE)工艺制备的镁锌系合金，细小的析出物中分布均匀，细化效果较好。此外，通过实现晶粒细化和织构控制，镁铝系合金(AZ31)在室温冲击应变速率为1.8×10~(-3)S^~(-1)~(-1)的条件下，获得了不低于50%的延伸率。在“扩散连接和搅拌摩擦焊接技术的建立”中，从压缩超塑性变形中的空洞消失模型推导出描述扩散连接条件的方程，结果表明，在最佳工艺条件下，AZ31合金的结合强度足以达到铝的1/3的结合时间。此外，对于纯镁，搅拌摩擦焊虽然没有获得足够的结合强度，但与该合金的结合强度达到了母材的90%以上。(4)在《薄板冲压成形工艺的建立》中，发现成形极限取决于冲头肩部拉伸弯曲的断裂极限，在473K或更低的温度加热可以改善成形极限。研究表明，拉伸试验难以评价的局部变形性对获得良好的冲压成形性能具有重要意义，并提出了用缺口弯曲试验评价成形性能的新方法。较少

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