Thermo-mechanical processing of high-manganese austenitic TWIP-type steels

The high-manganese austenitic steels are an answer for new demands of automotive industry concerning the safety of passengers by the use of materials absorbing high values of energy during collisions. The chemical compositions of two high-manganese austenitic steels containing various Al and Si concentrations were developed. Additionally, the steels were microalloyed by Nb and Ti in order to control the grain growth under hot-working conditions. The influence of hot-working conditions on recrystallization behaviour was investigated. On the basis of initial investigations realized by hot upsetting the thermo-mechanical conditions resulting in a fine-grained structure were designed. The sigma-epsilon curves and identification of thermally activated processes controlling work-hardening by the use of the Gleeble simulator were determined. It was found that the thermo-mechanical treatment conditions influence a phase composition of the investigated steels after solution heat treatment.