Effect of strain deformation rates on forming the structure and mechanical properties of high-manganese austenitic TWIP steels

Abstract

The aim of this paper is to determine the influence of strain rate on mechanical properties and structure of high-Mn austenitic TWIP steels. Deformation rates in a range from 0.001 to 1000 s−1 have a significant effect on forming the structure and mechanical properties of high-manganese austenitic TWIP-type steels. TWIP steels not only show excellent strength, but also have excellent formability due to twinning, thereby leading to excellent combination of strength, ductility and formability over conventional dual phase steels or transformation-induced plasticity steels. Also the strain energy per unit volume of advanced high-Mn TWIP steels containing Mn, Al, SI and some of that steels with Nb and Ti microadditions with various structures after their heat- and thermomechanical treatments increases considerably in dynamic conditions. The microstructure of investigated steels was determined in metallographic investigations using light, scanning and high-resolution transmission electron microscopes. Results obtained in static and dynamic conditions for newly developed high-manganese austenitic steels indicate the possibility and purposefulness of their employment for constructional elements of vehicles, especially of the passenger cars to take advantage of the significant growth of their strain energy per unit volume which guarantee reserve of plasticity in the zones of controlled energy absorption during possible collision resulting from the activation of twinning induced by cold working, which may result in significant growth of the passive safety of these vehicles’ passengers.