基于第一性原理的CrCuFeNiTi高熵合金涂层的相及稳定性分析

采用等离子弧在45钢基体上熔覆了CrCuFeNiTi高熵合金涂层,经X射线衍射分析涂层中的物相有BCC、FCC和Fe₂Ti相,并对BCC、FCC和Fe₂Ti相进行了成分测试,采用CASTEP中的虚拟晶体近似方法建立了BCC、FCC和Fe₂Ti相的晶体结构模型,基于第一性原理计算了涂层中BCC、FCC和Fe₂Ti相的晶格常数,并与涂层中BCC、FCC和Fe₂Ti相的X射线测试结果进行了比较,另外计算了BCC和FCC相的弹性常数C_ij、体积模量B、剪切模量G、杨氏模量E和泊松比ν。结果表明,涂层中BCC和FCC相以及Fe₂Ti的晶格常数计算值与试验值的误差为0.43%~3.05%,BCC、FCC和Fe₂Ti相的生成热均为负值且BCC和FCC相的弹性常数C₁₁、C₁₂和C₄₄满足立方结构高熵合金的力学稳定性限制条件,可知BCC、FCC和Fe₂Ti相是稳定的。另外由C₁₂-C₄₄>0,G/B<0.57,ν>0.26可知BCC和FCC相以金属键结合且呈现韧性的特征。

Phase and stability analysis of CrCuFeNiTi high entropy alloy coating based on first principles

CrCuFeNiTi high entropy alloy coating was deposited on 45 steel substrate by plasma arc. The phases of the coating were BCC, FCC and Fe₂Ti phase which analyzed by means of XRD, and the composition of BCC, FCC and Fe₂Ti phases were tested. The crystal structure model of BCC, FCC and Fe₂Ti phases were established by using the virtual crystal approximation method in CASTEP. The lattice constants of BCC, FCC and Fe₂Ti phases in the coating were calculated based on the first principles, and compared with the X-ray test results of BCC, FCC and Fe₂Ti phases in the coating. In addition, the elastic constants C_ij, bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν of BCC and FCC phases were calculated. The results show that the deviation between the calculated lattice constant of BCC, FCC and Fe₂Ti phase and the experimental value is 0.43%-3.05%. The heat of formation of BCC, FCC and Fe₂Ti phases is negative, and the elastic constants C₁₁, C₁₂ and C₄₄ of BCC and FCC phases meet the requirements of mechanical stability constraints of cubic high-entropy alloys, which show that BCC, FCC and Fe₂Ti phases are stable. In addition, the BCC and FCC phases are combined with metal bonds and exhibit toughness characteristics according to the calculation results of C₁₂-C₄₄>0,G/B<0.57,ν>0.26.