Application of the Kocks-Mecking model to tensile deformation of an austenitic 25Cr-19Ni steel

Stress-strain relationships obtained by tensile test below room temperature for an austenitic 25Cr-19Ni steel were analyzed by using the Kocks-Mecking model to make clear the effects of temperature and strain rate on flow stress. A temperature range used here is between 77 and 296 K, a strain rate range between 10(-9) and 10(-2) s(-1) and true strain below 0.2, where structure evolution depends on strain but scarcely on temperature and strain rate. This means that work-hardening rate is almost independent of test temperature and strain rate in the above ranges. Crosshead-arresting tests were performed to obtain flow stresses at 10(-9) s(-1) and the results suggested that the athermal stress could hardly be determined from the measurement of stress relaxation behavior at low temperatures. Flow curves obtained by the above deforming conditions are successfully described by using the Kocks-Mecking model with minor modifications. That is, we have claimed that the work-hardening consists of the thermal stress and the athermal stress. It should be noted that the flow curves for as hot-rolled specimens and for annealed specimens can be well simulated by changing the athermal stress. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.