(Ti/Zr/Hf/Sn/W)NbMoTaV高熵合金性能第一性原理计算分析方法

Investigation on Properties of(Ti/Zr/Hf/Sn/W)NbMoTaV High-Entropy Alloys Using First-Principles Calculation and Analysis Method

为解决作为高超声速火箭橇滑靴材料的难熔高熵合金WNbMoTaV在应用中呈现本征脆性、室温塑性韧性低等问题,采用第一性原理计算方法,用Ti、Zr、Hf和Sn替换其中易氧化、塑性较差的W元素,来探究替换元素对高熵合金塑性韧性性能的影响机制。通过理论公式计算(Ti/Zr/Hf/Sn/W)NbMoTaV合金的7种相形成规律参数和内聚能,确定其都为稳定单一的体心立方结构;进而构建出相应的模型计算了这5种难熔高熵合金的弹性性质。弹性常数、泊松比ν、Pugh比k、柯西压力C_(12)-C_(44)、Zener各向异性系数A^(Z)和Chung-Buessem各向异性系数A^(G)的计算结果表明:(Ti/Zr/Hf)NbMoTaV相较替换W前的强度明显下降,塑性少量提升,各向异性略有下降,但剪切各向异性有所增加,而将W替换成Sn导致材料的强度和塑性都略有下降,各向异性增加,剪切各向异性降低明显。态密度分析得出上述现象产生的原因主要是Ti、Zr、Hf、Sn会造成合金材料的成键稳定性和共价性降低,从而导致基体理论强度下降。此研究可为难熔高熵合金的成分设计、改善性能和进一步应用提供一定的参考。

In order to solve the problems of intrinsic brittleness and low room temperature plastic toughness of the refractory high-entropy alloy WNbMoTaV used as the material for the slide shoe of hypersonic rocket skids,first-nature principle calculations are conducted to investigate the influence mechanism of the substituting elements Ti,Zr,Hf and Sn on the plastic toughness performance of the high-entropy alloy for the oxidizable and less plastic W element.The seven phase formation law parameters and cohesion energy of the(Ti/Zr/Hf/Sn/W)NbMoTaV alloys are calculated by theoretical equation and it is determined that the NbMoTaV alloy is a stable and single BCC structure.Then corresponding models are constructed to calculate the elastic properties of these five refractory high-entropy alloys.Calculation results of elastic constants,Poisson’s ratioν,Pugh’s ratio k,Corsi pressure C_(12)-C_(44),Zener anisotropy coefficient A^(Z) and Chung-Buessem anisotropy coefficient A^(G) show that(Ti/Zr/Hf)NbMoTaV decreases significantly in strength,increases slghtly in plasticity and decreases slightly in anisotropy,but increases in shear anisotropy compared with that before the W replacement.When W is replaced by Sn the strength and plasticity of the material decrease slightly,the anisotropy increases,and the shear anisotropy decreases obviously.The reason for these phenomenons obtained from the density analysis of states is that Ti,Zr,Hf and Sn decrease the bonding stability and covalency of the alloy material,and thus decrease the theoretical strength.This study provides theoretical reference for composition design,performance improvement and further engineering applications of refractory high-entropy alloys.