Effect of Strain Rate on Deformation Behavior of Austenitic High Mn Steel at Cryogenic Temperature

DoctorIn recent years, austenitic high Mn steels have received a great deal of attention since they show an excellent combination of high strength and large ductility. It has been shown that the deformation behavior of these austenitic high Mn steels is strongly dependent on their stacking fault energies (SFEs); the steels show the transformation-induced plasticity (TRIP) for SFE ~45 mJ/m2 [4]. Mn and C effectively change the SFE and accordingly the steels containing (20-30) wt.% Mn and (0.4-1.2) wt.% C have SFEs in the range of 30 mJ/m2 and 40 mJ/m2 and usually exhibit TWIP phenomenon at room temperature, thus called as TWIP steels among various types of austenitic high Mn steels. An extraordinary combination of ductility and strength can be obtained in TWIP steels, where mechanical twinning γ ? γ`T proceeds gradually during deformation. The twinned crystal planes act as obstacles to dislocation motion, leading to dynamic Hall-Petch type strengthening. Considering that the application of these TWIP steels would be mostly in automobiles, the components made of TWIP steels would be subjected to not only quasi-static but also dynamic strain states such as during collision, but the effect of strain rate on the mechanical behavior of TWIP steels has seldom been studied and is not clearly understood. Understanding the behavior of TWIP steels at high strain rates is also important since these TWIP steels have a large potential for applications as structural components for several load bearing applications such as vessels, liquid nitrogen gas tank, etc. In addition, high strain rates will also play a role during sheet forming of TWIP steels. The objective of the present study is to study the effect of strain rate ranging from 10-3/s to 103/s at room temperature and cryogenic temperature on the deformation behavior of high Mn TWIP steel