Ti_(x)NbMoTaW系高熵合金性能的第一性原理计算

First-principles Calculations of Properties of Ti_(x)NbMoTaW High Entropy Alloys

NbMoTaW合金是目前研究极广泛的难熔高熵合金之一,具有高熵合金高强度、高硬度、耐磨损的优异性能,但其韧性塑性较差,极大影响了其在工程中的应用。本研究在NbMoTaW合金中添加不同比例的Ti元素以提高该合金的塑韧性,通过相形成参数计算确定了Ti_(x)NbMoTaW系合金的相结构为固溶体相,运用基于密度泛函理论的第一性原理方法计算合金晶格常数、基态能量、形成能及焓变值,分析了合金结构稳定性。通过计算合金不同Ti含量时弹性常数、弹性模量、B/G、泊松比ν、柯西压C_(12)-C_(44)等参数研究了合金弹性性质的变化规律。最后对电子态密度分析得知,合金体系成键共价性降低,金属键增强,弹性性质和态密度的结果表明添加Ti有助于该合金韧性的提高。此研究可为设计、改善难熔高熵合金性能提供一定设计思路和理论指导。

NbMoTaW alloy is one of the most widely studied refractory high entropy alloys.It has the excellent properties of high entropy alloy,high strength,high hardness and wear resistance,but its toughness is poor,which greatly affects its application in engineering.In this study,different proportions of Ti elements were added into NbMoTaW alloy to improve the toughness of the alloy.The phase structure of Ti_(x)NbMoTaW was determined to be solid solution phase by calculating the phase formation parameters.The crystal lattice constant,formation energy and enthalpy change of the alloy were calculated by the first-principles method based on density functional theory to analyze the structural stability of the alloy.By calculating the elastic constants,elastic modulus,B/G,Poisson ratioν,Cauchy pressure C_(12)-C_(44) and other parameters of the alloys with different Ti content,the elastic properties of the alloys were studied.Finally,the electron state density analysis shows that the bonding covalence of the alloy system decreases and the metal bond strengthens.The results of elastic properties and state density show that adding Ti can improve the toughness of the alloy.This study can provide some theoretical guidance and design ideas for designing and improving the properties of refractory high entropy alloys.