Effect of ART-Annealing Conditions on Microstructural Regulation and Deformation Behavior of 0.17C-9Mn-3.5Al TRIP-Aided Steel

The effects of annealing conditions on the microstructure and deformation mechanism of 0.17C-9Mn-3.5Al steel have been investigated. Through austenite reverted transformation (ART) annealing, a multiphase microstructure composed of alpha-ferrite, alpha-intercritical ferrite, alpha-austenite, and alpha'-martensite is obtained in as-forged specimens. For the specimen annealed at 750 degrees C for 60 min, a high volume fraction (42.19%) of retained austenite is attained, yielding a large total elongation (TE) of approximate to 38% and tensile strength (Rm) of approximate to 810 MPa and a two-stages work hardening behavior. The work hardening behavior analysis using the differential C-J model clarifies that the multistage can be mainly attributed to the discontinuous transformation induced plasticity (TRIP) effect, which is related to the volume fraction of retained austenite and its different stability levels as well as cooperative deformation of the multiphase microstructure. Thus, the active TRIP effect predominately affects the high strain stage, resulting in a higher work hardening ability and a increased plasticity.