2000 Volume 40 Issue Suppl Pages S164-S168
Structure evolution and deformation behavior of a 304 type austenitic stainless steel were studied in multiple compression at a temperature of 873 K (0.5 Tm) under a strain rate of about 10-3 s-1. The integrating flow curve shows a maximum at moderate strains around 1.5 followed by a minor strain softening at high cumulative strains above 3. The structural changes taking place during deformation can be characterized by the evolution of elongated subgrains with their low-to-middle angle boundaries as dense dislocation walls at low to moderate strains. These subgrains become more equiaxed and the subboundary misorientations gradually increase with increase in strain. The volume fraction of the highly misoriented substructure substantially increases upon multiple deformation to high cumulative strains above 3, finally leading to the development of a fine grained microstructure with an average grain size of about 300 nm. The mechanisms of such structural development as well as the relationship between microstructures and deformation behavior are discussed in details.