Abstract:
Metastable austenitic stainless steels undergo strain-induced martensitic transformation, where the metastable austenite phase is transformed to the thermodynamically more stable a'-martensite phase due to plastic deformation. The strain-induced martensitic transformation enhances the work hardening of the metastable austenitic stainless steels, and affects their ductility. This work is concerned about fmding the factors affecting the strain induced martensitic transformation and use them to simulate the phase transformation occurring during plastic deformation by using a mathematical model. As an application of simulation performed we have used this model for predicting stress strain response and martensite formation for different type of specimen.
Mechanical stability of the austenite was very critical factor for the TRIP effect. If transformation is exhausted at small plastic strains then necking resistance is not possible, and if the austenite is too stable then it does not contribute to strain hardening at . stress concentrations. So the moderate stability was required to see the influence of TRIP effect on plasticity.
We have performed uniaxial tensile test for investigating the TRIP effect in 1.4301 austenitic stainless steel and used magnetic techniques to monitor the progress of the austenite (y) — a' -martensite transformation. The amount of formed martensite. is strongly coupled to the hardening of the material so it was really necessary to examine the work hardening behaviour of the steel. The mathematical model used for the simulation of martensitic transformation is the integration of the Olson and Cohen equation by taking into account morphology, temperature and composition. This model does not take care of strain rate so we suppose that the test has been performed quasi-statically or at very low strain rate.
