Stability of retained austenite in a high strength TRIP steel

Mechanical properties and microstructure of a high strength TRIP steel with different heat treatments were investigated by tensile test,SEM,TEM,XRD and X-ray in situ measurement. The results show that the best mechanical properties are obtained when the steel is heat-treated at 800 ℃ for 3 min in two-phase region and then at 400 ℃ for 5 min in bainite region,the ultimate tensile strength is975. 68 MPa, the elongation is 27. 88%, and the product of strength and ductility is 27202 MPa%, respectively. The phase transformation from retained austenite to martensite occurs after yielding point due to strain induced transformation under the external force. The tendency of the retained austenite transformation decreases as the strain increases,indicating a progressive transformation from retained austenite to martensite by TRIP effect. The steel with stable film retained austenite shows better product of strength and plasticity.