Effect of concurrent recovery on Avrami exponent of the softening kinetics after hot deformation

Softening kinetics after hot deformation in the austenitic stainless steel, AISI 347, was investigated by stress relaxation tests in the temperature range of 970-1230 degrees C at the strain rates of 1-40 s(-1). Stress relaxation data were analyzed by both the conventional and the new method presented here to determine the Avrami exponent of n. By the conventional method, the exponent can be derived for recrystallization kinetics after the influence of the concurrent recovery is excluded; while the new method leads to an exponent to include contribution from both the recovery and recrystallization. It is found that the Avrami exponent derived in the latter case is significantly higher than that in the former case, indicating that an accurate evaluation of Avrami exponent for recrystallization kinetics requires a strict separation of recovery from recrystallization kinetics. (C) 2011 Elsevier B.V. All rights reserved.