轧制及退火后Al_(0.3)CoCrFeNi高熵合金的组织和力学性能

Microstructure and mechanical properties of Al_(0.3)CoCrFeNi high-entropy alloy processed by rolling and subsequent annealing

利用X射线衍射仪、扫描电镜、电子背散射衍射、透射电镜以及拉伸实验,研究了FCC结构Al_（0.3）CoCrFeNi高熵合金经90%压下量轧制及退火后的组织和力学性能。结果表明：经轧制及退火（600~1000℃）后,合金发生再结晶,富集Al、Ni原子的有序BCC相优先形成于再结晶FCC相的晶界处,且其体积分数随着退火温度上升先增大后减小。轧制显著强化该合金,随后600℃退火可实现不牺牲均匀塑性而进一步强化该合金的目的,升高退火温度则引起该合金强度下降,塑性增大。经800℃退火后合金表现出较为理想的强度-塑性匹配,其均匀伸长率为34.1%,且抗拉强度可高达935MPa,约是铸态合金（303MPa）的3倍,这主要归结于再结晶组织细化及有序BCC相的析出强化。

Microstructure and mechanical properties of as-cast FCC Al0. 3Co Cr Fe Ni high-entropy alloy after rolling and subsequent annealing were investigated by means of XRD,SEM,EBSD,TEM and tensile test. The results show that after rolling and subsequent annealing at600-1000 ℃,recrystallization occurs and Al Ni-rich ordered BCC phases preferentially precipitate at FCC grain boundaries. With annealing temperature increasing,the volume fraction of precipitations first increases and then decreases. This alloy can be dramatically strengthened by rolling and can be further hardened without sacrificing uniform ductility by subsequent annealing at 600 ℃,while a decrease of strength and an increase of ductility appear after further increasing annealing temperature. Specially,after rolling and annealing at 800 ℃,the alloy exhibits optimal mechanical performance with uniform elongation of 34. 1% and ultimate tensile strength of935 MPa,which is three times than that of the as-cast. This is ascribed to refined microstructure and precipitation hardening.