Plastic Strain due to Isothermal Transformation from Austenite to Ferrite in IF and Low Carbon Steels

Abstract

Apparent non-isotropic strain under external stress is quantified as a function of transformed fraction with dilatometric measurement and analysis for IF and low carbon steel. The non-isotropic strain of IF steel increases linearly with a transformed fraction, because fast transformation kinetics minimizes the contribution of creep in austenite and ferrite, and thereby the evolution of non-isotropic strain is mainly governed by transformation plasticity. For low carbon steel, the non-isotropic strain deviates from linear behavior in transformation segment where the creep in austenite and ferrite becomes remarkable due to the slow transformation kinetics. A diffusion controlled model describes well the effect of transformation kinetics on the evolution of non-isotropic strain during the transformation.