Abstract
Thermodynamics of martensite transformation in low alloy TRIP steel was evaluated. It follows from the calculation that ɛ phase might be formed at above room temperature in the low Mn steel. Tested steel was therefore prepared according to the estimation result. High volume fraction of retained austenite (above 20%) containing 1.37%C was obtained in the steel after continuous annealing treatment. Tensile test showed that the ultimate strength of the steel was 1248 MPa, elongation rate 25%, the product of strength and elongation rate 31200 MPa%, reaching the grade of the third generation automobile steel. XRD detection indicated that after tensile test there existed α′ martensite while TEM revealed that ɛ martensite also existed in the steel. Strengthening-toughening of the steel was thus raised due to the effect of transformation induced plasticity of two kinds of martensite. In addition, the phase stability of carbonitrates containing V was estimated and the complex micro-alloying effect was applied to the steel to control the size of austenite (about 1 μm) and enhance the stability of austenite.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
