Abstract: Scanning electron microscopy(SEM)， transmission electron microscopy(TEM)， X-ray diffraction(XRD) and tensile tests were used to investigate decomposition behaviors of the retained austenite(RA) in hot rolled TRIP steels with low Si and some Al elements during isothermal treatments. The results show that during different isothermal temperature， the RA can decompose into ferrite and carbides gradually with the isothermal time. When the isothermal temperature increases， the time required for the RA decomposition decreases. At different isothermal temperature， the variation tendency of tensile strength， total elongation and strength ductility balance of the tested steel decreases with the isothermal time. With different isothermal treatments， the variation of the volume fraction of the RA tends to be decreased， while the carbon content has little effect.

Key words: retained austenite, isothermal treatment, microstructures, mechanical properties, decomposition behavior