Effect of Strain Rate on the Strain-Induced [gamma] [arrow right] [alpha]'-Martensite Transformation and Mechanical Properties of Austenitic Stainless Steels

The effect of strain rate on strain-induced γ [arrow right] [alpha]'-martensite transformation and mechanical behavior of austenitic stainless steel grades EN 1.4318 (AISI 301LN) and EN 1.4301 (AISI 304) was studied at strain rates ranging between 3 × 10^sup -4^ and 200 s^sup -1^. The most important effect of the strain rate was found to be the adiabatic heating that suppresses the strain-induced γ [arrow right] [alpha]' transformation. A correlation between the work-hardening rate and the rate of γ [arrow right] [alpha]' transformation was found. Therefore, the changes in the extent of the [alpha]'-martensite formation strongly affected the work-hardening rate and the ultimate tensile strength of the materials. Changes in the martensite formation and work-hardening rate affected also the ductility of the studied steels. Furthermore, it was shown that the square root of the [alpha]'-martensite fraction is a linear function of flow stress. This indicates that the formation of [alpha]'-martensite affects the stress by influencing the dislocation density of the austenite phase. Olson-Cohen analysis of the martensite measurement results did not indicate any effect of strain rate on shear band formation, which was contrary to the transmission electron microscopy (TEM) examinations. The [beta] parameter decreased with increasing strain rate, which indicates a decrease in the chemical driving force of the γ [arrow right] [alpha]' transformation. [PUBLICATION ABSTRACT]