Modeling of strain-induced phase transformation in metastable austenitic Cr–Ni steels

Abstract A macroscopic constitutive model for the strain-induced martensite transformation observed in metastable austenitic stainless steels is presented. It models the material as an evolving two-phase austenite-martensite composite, where the plastic strains in each phase are computed using viscoplastic power-law relations. Two distinct hardening rules, one for austenite and the other for martensite, are employed to represent the disparities in their strengths and hardening abilities. The stress strain fields in the individual phases are homogenized using the Reuss/Sachs method to compute the macroscopic behavior. The phenomenological transformation kinetics model proposed by Stringfellow is directly adapted; it considers the influences of stress state, plastic strain, and temperature to model the evolution of martensite. Both the small- and large-strain formulations of the model are implemented as material routines in the finite element framework, and the material parameters in these formulations are calibrated using the experimental data obtained from a quasistatic uniaxial tension test performed on AISI 347. The calibrated model formulations are used to simulate isothermal quasistatic loading on a solid body with a center hole, and a comparison between the predictions from small- and large-strain models is presented. Furthermore, the influence of martensite evolution on necking in uniaxial tension tests is studied.