Quantitative Assessment of the Effect of Microstructure on the Stability of Retained Austenite in Multiphase TRIP Steels

摘要

A microstructure characterization technique has been developed to assess the effects of retained austenite grain size/morphology and other microconstituents on the stability of retained austenite in TRIP steels. EBSD and SEM have been used to identify micro-constituents in TRIP780 specimens after deformation to various strain levels by uniaxial tensile tests. It has been found that smaller grains of retained austenite are more stable than larger ones. A modified Burke - Matsumura model has been developed to describe the effect of grain size on the stability of retained austenite. Partial transformation of retained austenite grains occurs both during heat treatment and during deformation of TRIP steels. Partial transformation creates interface between martensite and retained austenite. The interface area increases with strain level except in the highest strain level of 25%.