CoCrFeMnNi高熵合金的相稳定性

Phase stability of CoCrFeMnNi high entropy alloys

通过分析CoCrFeMnNi高熵合金在1000、800和600℃退火后的组织和结构,研究了该合金的相稳定性。结果显示：CoCrFeMnNi高熵合金退火前为FCC单相固溶体,1000℃×72h退火后合金的组织和结构无变化;800℃退火后合金中析出了富含Cr元素的层片状第二相,析出相主要分布在晶界处;600℃退火试样析出了富Mn相。基于吉布斯自由能的热力学分析表明,合金体系的构型熵在高温时能够维持CoCrFeMnNi合金相结构的稳定性,中低温时会有第二相析出,因此CoCrFeMnNi高熵合金不能视作绝对稳定相。

The phase stability of CoCrFeMnNi high entropy alloys（ HEAs） was studied by analyzing its microstructure and structure after annealing at 1000,800 and 600 ℃,respectively. The results indicate that the alloy is a single-phase solid solution and remains in this state after a subsequent annealing at 1000 ℃ for 72 h. However,it is unstable and precipitates secondary phase at 800 ℃ and 600 ℃. A Cr-rich lamellar phase and a Mn-rich phase forms at 800 ℃ and 600 ℃,respectively. SEM images show that these precipitates are located at grain boundaries. At the same time,the thermodynamic analysis based on aibbs free energy shows that the configuration entropy can maintain the stability of the phase structure at high temperature,and there will be precipitation at lower temperature. Therefore,CoCrFeMnNi high entropy alloy can not be considered as absolute stable alloy.