Enhanced high-cycle fatigue resistance of 304 austenitic stainless steel with nanotwinned grains

Abstract Introducing high density of nanotwins (NT) into metals is regarded an effective strategy to achieve superior mechanical properties. Our study shows that heterogeneous structured 304 austenitic stainless steel comprising of NT and micrometer-sized grains with a lower strength exhibits a comparable fatigue strength and larger fatigue limit/strength ratio, compared to its counterpart comprising of grains with NT and dislocation structures, distinct from the traditional fatigue view. Such superior high-cycle fatigue resistance arises from a weakened strain-localized fatigue mechanism where some NT grains co-deform plastically with a large volume fraction of surrounding microsized grains with enhanced dislocation slipping and martensitic transformation.