Nanoindentation study on early-stage radiation damage in single-phase concentrated solid solution alloys

Abstract

Concentrated solid solution alloys (CSAs) comprising multiple components have unlocked novel pathways for materials design, particularly in enhancing radiation tolerance. It is imperative to detect early-stage radiation damage in CSAs to gain insights into damage initiation and accumulation mechanisms. In this study, nanoindentation is employed to assess the impact of irradiation on deformation mechanisms in single crystal CSAs, specifically NiCo, NiFe, and NiCoFeCr. It is discovered that pile-up behavior in CSAs significantly affected by irradiation: pile-up induces 10–20 % increase in the contact area before irradiation that is independent of the penetration depth but 20–30 % after irradiation, which substantially affects hardness analyses. Within the context of strain gradient plasticity theory, distinct radiation-induced hardening in three CSAs is interpreted by two components: one is from the radiation-induced defects, and the other is the increase in density of geometrically necessary dislocations (GNDs) associated with indentation size effect (ISE). Quantitative analysis shows that the radiation-induced defects produce obvious hardening in NiFe and NiCoFeCr sample, but not in the NiCo sample. Meanwhile, the irradiation induces a higher GND density in NiCo and NiFe, but not in NiCoFeCr, which is interpreted by the volume change of the plastic zone.