Dynamic Recrystallization in Austenitic Stainless Steel during Hot Working with Decreasing Deformation Temperature

The deformation microstructures and the mechanical properties of an advanced austenitic stainless steel subjected to hot forging with a decrease in deformation temperature from 1,323 to 1,073 K were studied. The deformation microstructures were characterized by the development of dynamic recrystallization (DRX), leading to a decrease in the mean grain size from 11 to 1 mu m as temperature decreased. Two DRX mechanisms, i.e., discontinuous and continuous ones, operated concurrently during the hot compressions. Corresponding true flow stress gradually increased approaching a steady-state deformation during each compression. The grain refinement was accompanied by an increase in the dislocation density, resulting in significant strengthening. The yield strength increased from about 600 MPa to almost 1,000 MPa as revealed by tensile tests at room temperature. Both the grain-size strengthening and the dislocation strengthening contributed to the overall strength of the processed steel samples with DRX microstructures.