investeInvestigation of two stage heat treatment on microstructure and mechanical properties of TRIP steel

The application of transformation induced plasticity (TRIP) steels is increasing because of their good strength and formability. The special microstructure of TRIP steel can be obtained by a two stage heat treatment contains intercritical annealing (IA) and intermediate ageing. The temperatures of these two stages have important effect on microstructure and mechanical properties of TRIP steels. In this paper the effect of heat treatment temperature on microstructure and mechanical properties of steels with chemical composition of Fe-0.2C-1.5Si-1.5Mn was investigated. XRd test was applied to determine the austenite volume fraction of microstructure. For measurement of strength and elongation of cases, tensile test was used and then the results were discussed by thermodynamic calculations. By the increasing of intercritical annealing temperature the volume fraction of austenite, its carbon and the strength of steels increased at first and then were decrease. Increasing of intermediate ageing temperature caused to decreasing of austenite volume fraction, its carbon content, strength and elongation of cases.