Mobility of point defects in CoCrFeNi-base high entropy alloys

The in-situ observation of microstructural evolution under electron irradiation was performed in order to experimentally estimate the mobility of vacancy and interstitial in 316 stainless steel and CoCrFeNi-base high entropy alloys. The vacancy migration energy in CoCrFeNiMn and CoCrFeNiAl 0.3 was estimated to be lower and higher compared with that in 316 stainless steel, respectively. While, the interstitial migration energy in those alloys seems to be almost the same. The increase in vacancy migration energy in CoCrFeNiAl0.3 is probably due to a strong interaction between vacancy and Al. The positron annihilation analysis revealed that vacancies might exist close to Co and Ni atoms in CoCrFeNi-base high entropy alloys. In addition, vacancies could also be captured by Mn and Al atoms in CoCrFeNiMn and CoCrFeNiAl0.3 , respectively. The electron- and ion-irradiation at 400 and 300 °C up to 1.5 dpa resulted in the precipitation of the intermetallic compounds, such as CoFe, NiFe in CoCrFeNiMn, and Ni 3Al in CoCrFeNiAl 0.3 . From these results, it is suggested that Co, Ni, Mn, and Al atoms could affect the vacancy mobility in HEAs, leading to the delay of microstructural evolution and the enhancement of precipitation under irradiation.