RECRYSTALLIZATION-TRANSFORMATION COMBINED REACTIONS DURING ANNEALING OF A COLD-ROLLED FERRITIC-AUSTENITIC DUPLEX STAINLESS-STEEL

Solid state reactions taking place during annealing of 20% cold rolled ferrite-austenite duplex stainless steel (DIN W.-Nr: 1.4462) have bee n studied by means of several complementary techniques: optical, scann ing and transmission electron microscopy, X-ray diffraction analysis, microhardness and ultramicrohardness measurements and magnetic phase d etection (ferritoscope). It has been found that after cold rolling aus tenite exhibited more strain hardening and a higher driving force for recrystallization than ferrite. Extensive recovery took place in ferri te during annealing, while the deformation substructure of austenite r emained nearly unrecovered until beginning of recrystallization. The r ecrystallization kinetics in ferrite was faster than in austenite. Rec rystallization in austenite occurred in a more discontinuous manner th an in ferrite. The eutectoid transformation of ferrite to sigma phase plus austenite slowed down recrystallization kinetics of both ferrite and austenite phases. A scheme is presented for sigma phase formation during recrystallization annealing.