Influence of Purity on the Dynamic Recrystallization of Metals and Alloys

The availability of high-purity metals and high-purity based alloys has recently allowed us to better understand the various processes of dynamic recrystallization (DRX) that take place during hot working. According to the mobility of dislocations and the subsequent efficiency of dynamic recovery (which mainly depends on stacking-fault energy), continuous (CDRX) or discontinuous (DDRX) dynamic recrystallization may take place. In aluminium, recent work has shown that a transition from CDRX to DDRX occurs with increasing purity, whereas in austenitic stainless steels close to the AISI 304L grade, DDRX is observed whatever the purity. A simple theoretical criterion for this transition is proposed and discussed. The key parameter is the grain boundary migration rate, whose temperature dependence is analyzed first. For the influence of purity, an indirect approach is then proposed on the basis of a model recently developed for CDRX.