Design of an effective heat treatment involving intercritical hardening for high-strength-high elongation of 0.2C-1.5Al-(6-8.5)Mn-Fe TRIP steels: microstructural evolution and deformation behaviour

摘要

We propose an effective heat treatment involving a combination of intercritical hardening and tempering to obtain high strength-high ductility in hot-rolled 0.2C-1.5Al-(6-8.5)Mn-Fe transformation-induced plasticity (TRIP) steels. An excellent combination of high ultimate tensile strength of 1045-1380 MPa and total elongation of 34-39% was obtained when the steels were subjected to intercritical hardening at 630-650 degrees C and tempered at 200 degrees C. Intercritical hardening impacted the co-existence of austenite, ferrite and martensite, such that the deformation behaviour varied with the Mn content. The excellent properties of the steels were attributed to cumulative contribution of enhanced TRIP effect of austenite and ferrite and martensite constituents. The discontinuous TRIP effect during tensile deformation involves stress relaxation and led to consequent enhancement of ductility.