Effect of Annealing Temperature on Microstructure,Mechanical Properties and Retained Austenite of 1 000 MPa Q＆P Steel

In this work effect of annealing temperature on microstructure,mechanical properties and retained austenite of 1 000 MPa Q＆P Steel were studied by means of SEM,EBSD,XRD and tensile test at room temperature.Results showed that the microstructure at room temperature was mainly composed of ferrite（F） + martensite（M） + retained austenite when the experimented steel was anneal at 800 ～900 ℃.With the increase of annealing temperature,the volume fraction of martensite increased,and the appearance of the internal lath of martensite became clearer.With the increase of annealing temperature,the volume fraction of retained austenite increases. The more grain boundaries,the denser the retained austenite. When anneal at 850 ℃,the best match of strength and plasticity of resulted steel was achieved,with the tensile strength of 991.33 MPa and the elongation of 18.58%,meeting the Q＆P 980 standard requirements.