Influence of heat treatment on microstructure and mechanical properties of a CMnSi TRIP steel using design of experiment

In the study, the effects of intercritical annealing (IA) and isothermal bainite treatment (IBT) parameters on microstructure and mechanical properties of a Fe-0.22C-1.4Mn-1.6Si cold rolled TRIP steel were investigated through the full factorial design of experiment. The cold-rolled steel samples with 80% thickness reduction were annealed at 780 degrees C for 5 to 15 minutes and fast-cooled to the bainite temperature region at 350 degrees C to 450 degrees C for 5 to 15 minutes, finally, cooled in water. The analysis of variance (ANOVA) and regression were used to evaluate the influence of factors on microstructure and mechanical properties of the studied steel. The results show that the volume fraction of retained austenite reach 15.8%, the ultimate tensile strength and the elongation at fracture were about 737.6 to 906.7 MPa and 25.3 to 36.4%, respectively. The relations between heat treatment parameters and microstructural characteristics, between these parameters and mechanical properties were established to use for choosing appropriate processing parameters according to desired mechanical properties. (C) 2018 Elsevier Ltd. All rights reserved.