Effect of carbon on strain-rate and temperature sensitivity of twinning-induced plasticity steels: Modeling and experiments

The temperature- and rate-dependent yielding of twinning-induced plasticity (TWIP) steels containing various carbon contents are investigated in the present work. The activation volume and the activation energy have been determined. The magnitude of these thermal activation parameters for high-carbon TWIP steels are largely different from those of conventional fcc metals, implying the fundamental role of carbon on the thermally activated dislocation activities in carbon-added TWIP steels. A constitutive model, which rationalizes yielding as the thermally assisted bowing out of dislocations under the pinning effect of carbon solutes, is proposed, and for the first time quantitatively predicts the thermal activation parameters of TWIP steels as a function of carbon content. Based on the modeling results of thermal activation parameters, the overall temperature- and rate-dependent yield stresses of TWIP steels containing various carbon contents are predicted, showing good agreements with experimental results. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.