Fundamental Study of the Austenite Formation and Decomposition in High Strength Low-Si, Al added Nb-Mo TRIP Steels

摘要

TRIP (Transformation Induced Plasticity) steels are under development for automotive applications that require high strength and high formability. In this study, the formation and decomposition behavior of austenite from the intercritical (alpha + gamma) region in a series of 0.15C-0.3Si-0.15Mo-0.03Nb steels with and without Al additions were evaluated. In addition, the systematic study of the recrystallization of ferrite during intercritical annealing was also investigated. The effect of the initial hot band microstructure on the formation of intercritically annealed austenite and the decomposition products of austenite during different thermal cooling paths from the intercritical region were defined and quantified. The resulting microstructures exhibited tensile strengths in excess of 790 MPa with elongations equal to or better than 25 percent. The results of this investigation will be presented and discussed in this paper.