Microstructure development by thermomechanical processing in duplex stainless steel

In the case of two-phase alloys, a refinement matrix phase and a uniform distribution of second phase are important to improve mechanical properties. In this paper, microstructure change of α (ferrite)+γ (austenite) two-phase structure, especially microduplex structure consisting of α and γ in a fine-grained form (1-3μm), in the duplex stainless steel by various thermomechanical processings and heat treatments is briefly reviewed. Main topics are as follows, 1) formation process of fine-grained α+γ structure (microduplex structure) by various thermomechanical processings, 2) nature of microduplex structure and its stability during prolonged aging, 3) microstructure change of microduplex structure by annealing after heavy cold rolling and 4) microstructure change of microduplex structure during superplastic deformation.