Strain-induced grain evolution in an austenitic stainless steel under warm multiple forging

The dynamic processes of ultrafine grain evolution in an S304H austenitic stainless were studied in multiple forging tests at temperatures ranging from 500 degrees C to 700 degrees C. The multiple forging was accompanied by the development of dynamic recrystallisation (DRX), which resulted in the formation of ultrafine grained structures. The size of the DRX grains decreases from 0.3 mu m to 0.1 mu m with a decrease in the temperature from 700 degrees C to 500 degrees C. The continuous DRX makes the main contributions to the overall recrystallisation process, although the discontinuous DRX plays an important role in the new grain development at moderate to large strains at 700 degrees C. The variation in the DRX mechanisms results in a change in the DRX kinetics. The fraction of high-angle boundaries can be expressed as F-HAB similar to 0.2 epsilon in the range of 0 < epsilon < 2 for processing at 500-600 degrees C, whereas F-HAB similar to 0.45 epsilon was obtained in the range of 1.2 < epsilon < 2 at 700 degrees C. (c) 2012 Elsevier B.V. All rights reserved.