THE EFFECT OF STRAINING BEFORE AND DURING AUSTENITE TO FERRITE TRANSFORMATION ON THE FINAL CHARACTERISTICS OF Si – Mn TRIP STEELS

TRIP (TRansformation- Induced- Plasticity) behaviour is a powerful mechanism to improve mechanical properties. The basis of TRIP phenomena is the transformation of retained austenite with optimum characteristics (volume fraction, stability, size and morphology) to martensite during deformation at room temperature. Accordingly, the first requirement to obtain desired TRIP effects is to produce an appropriate microstructure. Thermomechanical processing is an effective method to control the microstructural evolution thereby mechanical properties in TRIP steels. This work deals with a TRIP steel containing 0.2%C, evaluating the effects of straining before and during ??? transformation on its final characteristics, using hot compression tests. The results revealed that straining in the two phase region (dynamic transformation) not only reduces the ferrite grain size more significantly, but also increases the retained austenite volume fraction. Accordingly the final mechanical properties were also improved