具有BCC或FCC晶体结构的固溶体高熵合金设计

Design of solid solution high entropy alloys with BCC or FCC crystal structures

高熵合金最初报道于21世纪初期,该类合金具有较高的混合熵值,使其具有优异的热稳定性;较大的晶格畸变,产生了强烈固溶强化效果;较大的负焓值导致在晶粒内部形成团簇结构,有效阻碍了位错运动,进一步提高了合金强度。高熵合金独有的这些特性,使其在低温和高温条件下均有望表现出优异的物理性能和力学性能,引起了广泛的关注,研究报道呈爆发性增长。本文根据已有的BCC和FCC结构高熵合金物理-力学性能数据,分析了电子浓度、晶格常数、原子错配度、混合焓、硬度、弹性模量和归一化硬度等参数之间的关系,提出了BCC和FCC晶体结构的高熵合金弹性模量和硬度的经验计算公式,在此基础之上,综合考虑合金密度、塑性和服役工况等条件,提出了BCC和FCC结构的高熵合金成分设计方法。最后指出高熵合金的持久性能、大尺寸铸锭的成分和性能均匀性以及大尺寸合金锭的制备是高熵合金工程应用需解决的关键问题。

High entropy alloys(HEAs)were first reported in the early 2000s.High mixing entropy of the HEAs makes it present good thermal stability.Meanwhile,the large lattice distortion in the HEAs leads to significant solution strengthening.Additionally,cluster structures are formed within grains due to the large negative enthalpy.Consequently,the movement of dislocation is effectively hindered,and the strength of the HEAs is remarkably improved.Given to these unique characteristics,the HEAs is expected to have excellent physical and chemical properties at low and high temperatures.As a result,the HEAs have become a hot area with lots of published research papers.Based on existing physical and mechanical properties of the HEAs with BCC and FCC structure,relation among electron concentration,lattice constant,atomic mismatch,mixing enthalpy,hardness,elasticity modulus and normalized hardness were analyzed to develop a formula calculating elasticity modulus and hardness of the HEAs.On this basis,the composition design method of the HEAs with BCC and FCC structures is established by considering density,ductility and working environment.Finally,it is pointed out that the persistent strength of HEAs,the uniformity of composition and properties of large-sized ingots,and the preparation of large-sized alloy ingots are key issues that need to be addressed in the engineering application of HEAs.