Interaction between recrystallization and helium behavior in cold-rolled nickel

Introducing a high density of defect sinks is a promising approach to relieve helium embrittlement in structural alloys for future fusion energy applications. However, the interaction between preset defect evolution and helium behavior at elevated temperatures, which could lead to dramatic changes of microstructure and properties of alloys, is still not well understood. In this contribution, cold-rolled nickel subjected to He ⁺ irradiation at 500 °C was investigated to uncover the interaction process and the consequent microstructure evolution. Our experimental results revealed that during the initial period partial recrystallization and grain growth were unaffected by He ⁺ irradiation, leading to the formation of coarse grains. With the increasing of helium concentration, helium bubbles retarded dislocation rearrangement and grain boundary migration in the remaining recrystallization areas, and meanwhile the stabilized grain boundaries facilitated helium bubble coarsening and bubble-to-void transformation. Such interaction ultimately led to the retention of fine grains with severe swelling and hardening.