Mechanism of dynamic continuous recrystallization during superplastic deformation in a microduplex stainless steel

Microstructural evolution during the cyclic cold-rolling and annealing process in an (alpha + gamma) microduplex stainless steel, which consists of alpha subgrains and fine gamma particles, has been studied in detail with the aim of clarifying the mechanism of dynamic continuous recrystallization. A continuous increase in a subgrain boundary misorientation is obtained by the present processing where grain boundary sliding does not occur and the effect of increasing boundary misorientation with cumulative strain is comparable to those observed in dynamic continuous recrystallization of superplastic aluminium alloys. The increase in boundary misorientation is accounted for by the absorption of dislocations into subgrain boundaries during annealing, dislocations which had operated to accommodate the plastic strain incompatibility of the neighboring phases undergoing slip deformation. The present results show that grain boundary sliding is not indispensable but the difference in accommodation deformation between adjacent subgrains is of great importance for the dynamic continuous recrystallization during superplastic deformation. Copyright (C) 1996 Acta Metallurgica Inc.