X-Ray Residual Stress and Strain-Induced Transformation of Retained Austenite in TRIP-Aided Dual-Phase Steels

Abstract

The effects of strain-induced transformation (SIT) on X-ray residual stress of retained austenite islands in TRIP-aided dual-phase steels were examined under uniaxial tension, and were discussed using a micromechanics theory. If the retained austenite particles are stable against the SIT and strain hardening, high tensile residual stress of 100 to 200 MPa occurs in the particles. The stress corresponds to that estimated from the micromechanics theory. In such a case, the retained austenite particles effectively increase the internal stress of the ferrite matrix similar to bainite and martensite particles. When the retained austenite particles easily transform to martensite during straining, the residual stress is decreased by plastic relaxation resulting from expansion and shear strains on transformation, although the strain-induced martensite increases the flow stress of the steels.