Hot ductility behaviour of high-Mn TWIP steels

Abstract

The hot ductility behaviour of four high-Mn TWIP steels has been studied by hot tensile testing in the temperature range 700–1300°C at a strain rate of 1s−1. For all the studied steels with the single-phase austenitic structure, the hot ductility based on the reduction of area of tensile strained specimens is good. In the temperature range 1000–1200°C, dynamic recrystallization takes place and consequently the ductility is enhanced. Grain refinement by reheating at the lower reheating temperature (1150°C) significantly improves the hot ductility through inducing faster dynamic recrystallization. During high temperature deformation, 1.5wt.% of Al alloying is found to have a beneficial effect on the hot ductility due to strengthening of the steel, whereas the 0.019wt.% Nb alloying has insignificant effect. With high Al (3wt.%) and Si (3wt.%) alloying, the formation of ferrite phase at high temperatures along the austenite grain boundaries has the most deleterious effect on the hot ductility behaviour. Grain boundary sliding was recognized as the failure mechanism in the studied steels.