Micro/nano mechanical properties differences of shallow irradiation damage layer revealed by a combined experimental and MD study

Micropillar compression and nanoindentation techniques are both adopted to measure the mechanical properties in multi-energy He ion-irradiated Ni-based samples to study their relationship, and a distinct variation is observed. TEM characterization of the microstructure evolution and calculations based on the DBH model indicate that irradiation defects are not responsible for the observed variation. Subsequently, a comparative analysis of these two methods is simulated and their mechanisms are investigated using MD. Several factors, including activation of various slip systems, plastic area, and surface absorption, account for the differences observed in indentation and pillar compression tests, leading to the distinct evolution of internal initial dislocation lines, which significantly contribute to additional hardening in indentation tests.