Effect of temperature and strain rate on strain hardening and deformation mechanisms of high manganese austenitic steels

Abstract

Abstract The effect of temperature and strain rate on the mechanical properties of three Fe – Mn austenitic steels with Mn contents of 20 mass.% or above has been studied by tensile tests performed at strain rates ranging from 3 × 10−3 to 200s−1 and at temperatures between −160 and +140 °C. In these steels mechanical properties and strain hardening behaviour result from the competition between different deformation mechanisms including homogeneous or inhomogeneous dislocation glide, strain induced twinning or martensite formation. Thus, the microstructure evolution during deformation was investigated. For two of the steels, a relation of the deformation mechanisms (twinning and dislocation glide) at room temperature with the grain size was found. On the other hand, for the third steel at temperatures lower than 60 °C martensite is progressively formed during deformation. For the three steels, a decreasing volume fraction of twins or martensite with increasing testing temperature was found leading consequently to a decrease in flow stress and strain hardening.