A simple kinetics model for strain-induced martensitic transformation in metastable austenitic stainless steels

A model based on the Chapman-Richards growth function was proposed for investigating the strain-induced martensitic transformation kinetics in austenitic stainless steels. This model was formulated as f α' / f sat = {1-exp(- bε )} c , where f α' and f sat represent the volume fraction and the saturated volume fraction of α΄-martensite, respectively. In this equation, ε represents the equivalent strain based on the von Mises criterion. Moreover, the value of c was optimized as 17 and b was shown to be a viable metastability parameter. The value of b can readily be obtained by finding the slope of the fitted line on the plot of ln{1-{ f α' / f sat } 1/17 } versus - ε with the intercept of zero, without the need for non-linear regression, in contrast to the competitive models. The applicability of the developed model was evaluated by consideration of deformation temperature, strain rate, and mechanical loading conditions as the deformation parameters, initial austenite grain size as a microstructural parameter, and stacking fault energy (SFE) as a representative of the chemical composition of the investigated alloys. It was shown that the model based on the Chapman-Richards growth function is capable of investigating the α΄-martensite transformation kinetics and the b parameter can reasonably be correlated to the parameters responsible for the change in metastability of the material. The applicability of this simple model was also compared with the famous Olson-Cohen model, demonstrating the merit of the proposed model as an alternative model to be used in future investigations.