The stability of the retained austenite (RA) in the microstructure of TRIP steels is its resistance to deformation induced martensite transformation. RA stability is an important factor in the formability of TRIP steel sheet and in its post-forming energy absorption capability. The current study is a systematic investigation of the effects of microstructural variables on RA stability. Four model microstructures were produced in a 0.2C - 1.5Si - 1.5Mn steel, which represent the range of morphologies and the distribution of RA seen in TRIP steels. The microstructures were characterized by optical and electron metallography, and neutron diffraction. RA stability was determined by neutron diffraction measurements of the amount of RA transformed per unit strain during in-situ uniaxial tensile tests. The results show correlations between RA stability and the dimensions of elongated RA grains. Coarser RA grains were less stable than finer grains. Equiaxed RA grains were more stable than expected.
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