On strengthening of austenitic stainless steel by large strain cold working

Abstract

The tensile properties of an S304H austenitic stainless steel processed by large strain cold rolling were studied. Cold rolling was accompanied by the deformation twinning and martensitic transformation. The fraction of strain-induced martensite comprised 0.65 after cold rolling to a total strain of 4. The transverse grain size progressively reduced to about 200 nm in both the austenite and martensite phases. The deformation microstructures were characterized by large internal distortions, which were attributed to high dislocation density well above 1015 m-2. Cold rolling resulted in significant strengthening. The yield strength increased from 290 MPa in the initial annealed state to 2 050 MPa in the sample subjected to cold rolling to a total strain of 4. The strengthening could be adequately explained by increasing the dislocation density. In the framework of dislocation strengthening model the austenite and strain-induced martensite provided equal fractional contribution to the overall strength of the rolled steel.