Load-dependency of damage process in tension-compression fatigue of microscale single-crystal copper

This study aims to investigate the load-dependency of damage process of microscale single-crystal copper with single slip system. A series of fully-reversed tension-compression fatigue experiments involving in situ observations are conducted by constant displacement. It is found that load amplitude significantly affects the formation of extrusion/intrusion at early stage. A lower load threshold for crack initiation is observed. Above the load threshold, no significant load-dependency of fatigue crack initiation is observed. Moreover, Δτ_RSS/2 monotonically increases with increasing γ_pl in contrast with “plateau” regime for bulk coppers. The results indicate a new fatigue mechanism for crack initiation in microscale single-crystal copper.