Effects of strain rate on mechanical properties of heterogeneous nano-structured SUS316LN stainless steel: Revealed by in-situ X-Ray diffraction at synchrotron radiation facility

A SUS316LN austenitic stainless steel was heavily cold rolled to develop heterogeneous nano (HN)-structure. And the effects of strain rate on the tensile deformation behavior of the HN-structured SUS316LN stainless steel were investigated. For this purpose, changes in lattice defect densities, such as dislocation density and stacking fault probability, during the tensile tests were investigated by means of in-situ X-ray diffraction (XRD) measurements at a synchrotron facility. The strength and elongation to failure simultaneously increased with increasing applied strain rate. The analyses of XRD profiles and microstructural observation revealed that twin fault probability as well as dislocation density and stacking fault probability increased with increasing strain rate. The more enhanced formation of ultra-fine twins by the increase in strain rate led to higher work hardening and resulted in more excellent strength/ductility balance.