Effect of Strain Rate on the Formation of Strain-Induced Martensite in AISI 304L Stainless Steel

Abstract

The effect of strain rate on the stress–strain response and the austenite to strain-induced α′-martensite transformation of austenitic steel 304L was studied. Compression tests were carried out at room temperature in the strain rate range of 10−3 to 103 s−1 and the evolution of martensite was quantified using a ferritoscope. Higher strain rates resulted in lower strain-induced α′-martensite. Strain incremental tests were carried out at 1 s−1 to simulate isothermal tests and to delineate effect of adiabatic heating on the α′-martensite transformation. Strain rate change tests were also carried out to determine the effect of prior strain rate history on the strain-induced α′-martensite content. These experiments showed that apart from the effect of adiabatic heating at high strain rates on the α′-martensite content, there is an additional effect of strain rate. While the adiabatic heating effect could be based on the increase in stacking fault energy (reduction of stacking fault width) with temperature, the additional effect due to strain rate was explained based on the expected reduction in stacking fault width with increasing strain rate.