Visualized understanding and engineering of directional atomic bonding -Using the conventional shear -synchroshear transition in silicides with the C40 structure as a vehicle -

过渡金属障碍是指那些特别形成的、具有IVa ~ VIA组的Refractory金属的物质，在周期表中对结构应用的高温引起了可考虑的注意，因为他们的高温度、体内氧化物抵抗力、抵抗力、相对低密度和高热量条件。这些转换金属障碍，除了ZrSi D22-D2和HfSi-D22-D2与C49结构，水晶化为C11 b、C40和C54类型的三种结构之一，它们都是相对简单的，而且彼此更接近。这三种结构的相对相位稳定性与这些结构中的直接原子绑定的性质密切相关。The deformation mechanism of transition metal disilicides with these structures was studid putting stress on the effect of atomic bonding on their deformation.Transition metal disilicides with the three crystal structures were found to be classified into two *oups，i.e.one group including CrSiイエD22エD2 whose plastic flow is observed only Above 700℃。两组硅的变形性之间的差异与分散的核心结构的差异密切相关;与Nb、W、Re和A1一起研究了MoSi-D22-D2批准的蠕变行为和蠕变强度，从1200 ℃到1400℃的温度范围。[001]方向的蠕变率是常规压缩测试中最难的方向，它显著地改进了与Re， Nb， W和A1的允许。对添加Re和Nb来说，改进的程度是相当大的。creep rate attained for Re-bearing MoSi D22 y D2 is comparable to that obtained for the most advanced Si D23 y D2N y D24 y D2-based composites in tension。

Transition metal disilicides, in particular those formed with refractory metals of groups IVa 〜 VIa in the Periodic Table have drawn considerable attention for structural applications at high temperatures because of their high melting temperature, intrinsic oxidation resistance, resistance, relatively low density and high thermal conductivity. These transition metal disilicides, except ZrSiィイD22ィエD2 and HfSiィイD22ィエD2 with the C49 structure, crystallize into one of the three structures of the types C11b, C40 and C54, which are all relatively simple and closely akin to each other. The relative phase stability of these three structures is closely related with the nature of directional atomic bonding in these structures. The deformation mechanism of transition metal disilicides with these structures was studied putting stress on the effect of atomic bonding on their deformation.Transition metal disilicides with the three crystal structures were found to be classified into two *oups, i.e. one group including CrSiィイD22ィエD2 whose plastic flow is observed only above 700℃. The difference in deformability between the two groups of silicides is closely associated with the difference in the core structure of dislocations.The creep behavior and creep strength of MoSiィイD22ィエD2 alloyed with Nb, W, Re and A1 was also studied in the temperature range from 1200 to 1400℃. The creep strain rate for the [001] orientation, which is the hardest orientation in conventional compression tests, is significantly improved upon alloying with Re, Nb, W and A1. The extent of improvement is significantly large for adding Re and Nb. The creep rate attained for Re-bearing MoSiィイD22ィエD2 is comparable to that obtained for the most advanced SiィイD23ィエD2 NィイD24ィエD2-based composites in tension.