Retransformation (alpha '->gamma) kinetics of strain induced martensite in304 stainless steel

Coupons of austenitic 304 stainless steel (gamma) were transformed to appro ximately 90% martensite (alpha') and 10% austenite by rolling at 77 K. Subs equently the reverse alpha' --> gamma transformation was instigated by heat ing the coupons to 680 degrees C. The retransformation was monitored, in si tu, by dilatometry and neutron Bragg edge diffraction (BED). Results from t he two techniques show good agreement and suggest that the transformation k inetics are best described by two Avrami exponents, n = 2.5 and n = 0.2 res pectively. A limited discussion of the lattice parameter evolution during t he transformation is included. Possible mechanisms for growth dynamics and stress relaxation are discussed. (C) 2000 Elsevier Science S.A. All rights reserved.