Investigation of irradiation resistance characteristics of precipitation strengthened high-entropy alloy (CoCrFeNi)95Ti1Nb1Al3 using slow positron beam

Abstract A high-entropy alloy (HEA), (CoCrFeNi)95Ti1Nb1Al3, with a tensile strength approximately 60% higher than that of the equiatomic high-entropy alloy CoCrFeNi was developed. The increase in tensile strength results from the formation of Ni, Ti, Nb, and Al-rich precipitates, having a face-centered cubic (FCC) L12 type crystal structure, in the alloy during aging. To investigate the irradiation resistance of this alloy, it was irradiated up to 1.5×1019 ions/m2, corresponding to 1.65 displacements per atom (dpa) at the peak damage, at 300, 573, and 773 K using high-energy 2.5 MeV Fe ions. Applying a slow positron beam, the formation of defect clusters induced by ion irradiation and the thermal stability of defects formed at 300 K were investigated. Vacancy clusters formed after irradiation with 5.0×1018 ions/m2 at 300 K. Irradiation above this fluence at 300 K, and at the same fluence at 573 K did not significantly affect the formation of vacancy clusters. However, no vacancy clusters were formed after irradiation at 5.0×1018 ions/m2 at 773 K. The high-temperatures irradiation of this HEA hinders the formation of vacancy clusters. The irradiation resistance of the (CoCrFeNi)95Ti1Nb1Al3 HEA was excellent.