Temperature-dependent helium induced microstructural evolution in equiatomic NiCo and NiFe concentrated solid solution alloys

Irradiation temperature and the species of elemental constituents are two pivotal factors in determining the helium (He) radiation behaviors. However, their synergistic effect on the He-induced defect evolution in single-phase concentrated solid-solution alloys (SP-CSSAs) has rarely been studied. In this work, the evolution of He cavities and dislocation structural damages in two equiatomic SP-CSSAs, i.e., NiCo and NiFe, were investigated at 673 K, 773 K and 873 K with 275 keV He⁺ ions. He cavity formation behaviors were diverse at different temperature regimes. NiFe was found to have a stronger suppression effect on He cavity growth at 673 K. However, with the increasing temperature, a more pronounced increment of He cavity size was exhibited in NiFe. Unlike the evolution of He cavities, the growth of dislocation loops tends to be delayed in NiFe over the studied irradiation temperatures. The underlying mechanisms for the temperature-dependent defect evolution in NiCo and NiFe are discussed.