Stacking fault energy and electronic structure of molybdenum under solid solution softening/hardening

固溶软化/硬化下钼的层错能与电子结构

Ab initio calculations are used to understand the fundamental mechanism of the solid solution softening/hardening of the Mo-binary system.The results reveal that the Mo-Ti,Mo-Ta,Mo-Nb,and Mo-W interactions are primarily attractive with negative heats of formation,while the interactions of Mo-Re,and Mo-Zr would be mainly repulsive with positive heats of formation.It is also shown that the addition of Re and Zr would cause the solid solution softening of Mo by the decrease of the unstable stacking fault energy and the increase of ductility.On the contrary,the elements of W,Ta,Ti,and Nb could bring about the solid-solution hardening of Mo through the impediment of the slip of the dislocation and the decrease of ductility.Electronic structures indicate that the weaker/stronger chemical bonding due to the alloying elements should fundamentally induce the solid solution softening/hardening of Mo.The results are discussed and compared with available evidence in literatures,which could deepen the fundamental understanding of the solid solution softening/hardening of the binary metallic system.

用第一性原理计算方法研究了钼二元系固溶体软化/硬化的基本机理。结果表明,Mo-Ti、Mo-Ta、Mo-Nb和Mo-W之间的作用主要是相互吸引,具有负的生成热,而Mo-Re和Mo-Zr之间的作用主要是相互排斥,具有正的生成热。Re和Zr的加入会降低钼的堆垛层错能,提高合金的塑性,从而导致钼的固溶软化;而W、Ta、Ti、Nb等元素通过阻碍位错滑移和塑性下降,使Mo固溶硬化。电子结构表明,合金元素导致的弱/强化学键合从根本上诱导了钼的固溶体软化/硬化。本文对计算结果进行讨论,并与文献中已有的证据进行了分析比较,加深了对二元金属体系固溶体软化/硬化的基本认识。