Effect of Surface Shot Peening and Annealing Treatment on the Microstructure and Properties of Fe - 30Mn - 3Al- 3Si TWIP Steel

Surface shot peening and annealing heat treatment were applied to the Fe-30Mn-3Al-3Si TWIP steel to achieve toughening. The effects of shot peening and shot peening combined with annealing on the microstructure of TWIP steel were analyzed by means of metallurgical microscopy, X-ray diffraction and transmission. The hardness distribution, mechanical properties and work-hardening behaviors of the original samples, shot peened and shot peened + annealed samples were analyzed by using the micro-Vickers hardness tester and universal material testing machine. Results showed that the strong plastic deformation on the surface of TWIP steels was induced by shot peening, which resulted in the formation of highly deformed layer containing dislocation clusters of 60～100 nm size and transition layer containing micro and nanoscale deformation twin structures. This nano-micron scale grain size gradient structure could significantly increase the hardness of the highly deformed layer on the surface of TWIP steels to 366 HV0.1