Effects of Heat Treatment Processes on Microstructures and Properties of the Vanadium-alloyed Cold-rolled TRIP Steel

The microstructures and properties of vanadium-alloyed cold rolled TRIP steel were investigated by salt-bath heat treatment and methods of property testing and microstructure observation. The results show that all the tensile strength of the samples can reach 700 MPa in the certain heat treatment, and the best mechani-cal properties with 514 MPa yield stress, 738 MPa tension stress, 29% elongation and 21 402 MPa·%, re-spectively, can be achieved. As the intercritical annealing temperature increasing, the volume fraction of aus-tenite increases accordingly. So the hardening phases such as bainite and martensite increase to make the strength increasing and the ductility decreasing. The positive effect of vanadium on austenite is not apparent,which may be associated with the short annealing time and the precipitation of vanadium carbides in the bain-ite zone which can reduce the stability of retained austenite by consuming the carbon element.