W–Y二元合金力学性质的第一性原理计算§

Mechanical Properties of W–Y Alloys by First-Principles Calculations

摘要:

W-Y二元合金是一种具有潜力的核聚变装置第一壁材料, 其力学性质对材料的加工和应用有重要影响. 然而, 目前文献中对W-Y合金的力学性质还鲜有报道. 因此, 本文采用基于密度泛函理论的第一性原理方法研究了钇的含量对W-Y二元合金力学性质的影响, 精确计算了W_1-xY_x(x = 0.0625, 0.125, 0.25和 0.5) 合金的力学常数, 并对其力学特性进行分析. 研究结果表明, W-Y合金的弹性常数、体模量、杨氏模量以及剪切模量随Y的含量的增加而成非单调性减小, 表明Y对W材料的合金化降低了材料的机械强度. 然而, 基于力学特性B/G、泊松比ν和柯西压力C"等分析, Y的合金化对W的延展性和韧性有明显的提高. 当Y的含量为0.25时, 可有效改善W-Y合金的延展性和抵抗变形能力. 通过态密度分析,W-Y合金的金属性随Y含量的增加先减弱而后增强.

Abstract:

W-Y binary alloy has potential applications in the first wall material for nuclear fusion device. Mechanical properties have important effects on material processing and application. However, the mechanical properties of W-Y alloy are rarely reported in the literature. In this paper, the effect of yttrium contents on the fundamental mechanical properties of W-Y alloys has been studied by using first-principles method based on the density functional theory. The mechanical constants of W_1-xY_x (x=0.0625,0.125,0.25,0.5) alloys were calculated for different compositions in solid solution model. According to the calculated mechanical constants, the mechanical properties are analyzed. Our results show that the elastic constants, bulk modulus, Young’s modulus and shear modulus of W-Y alloys decrease non-monotonically with the increase of Y concentration, indicating that the doped Y decreases the mechanical strength of W materials. Based on the mechanical characteristic, such as B/G, Poisson’s ratio ν and Cauchy pressure C", the ductility and toughness of the W-Y alloys are significantly improved with the increase of Y concentration. When the Y contents reaches 0.25, the resistant and ductility of W-Y alloy are largely enhanced. Through the analysis of the density of states, W-Y alloy metallic properties begin decreases and then increases as the concentration of Y increases.