Dynamic thermo-mechanical response of austenite containing steels

Abstract

Austenite can be made thermally stable at room temperature by alloying the steel for example with nickel or manganese, which brings the martensite start temperature of the alloy below RT. Also low alloy steels can contain relatively high amounts of (retained) austenite brought about by appropriate heat treatments, which increase the carbon content of some of the austenite grains to such high levels that thermal martensite transformation does not take place in them. Well known steels containing stable or metastable austenite at room temperature are austenitic and duplex stainless steels, Hadfield manganese steels, low alloy TRIP steels, and high manganese TRIP and TWIP steels. Depending on the deformation temperature and strain rate, deformation induced martensite transformation and/or twinning, or the lack of them, can lead to quite extraordinary behavior and strength and elongation combinations. In this paper, the strain hardening behavior and strain rate sensitivity of several fully or partially austenitic steels are discussed in view of their microstructural development during deformation. The discussion is based on the experiments conducted on these materials in wide ranges of strain rate and temperature with conventional materials testing machines and various Hopkinson Split Bar techniques.