The effect of TiN inclusions on the fracture mechanism of 20CrMnTi steel with lath martensite

This study aims to investigate the effect of TiN inclusions on the fracture mechanism of 20CrMnTi steel with martensite. Size of martensite packets, blocks and TiN inclusions were characterized, and the room-temperature tensile properties, impact toughness and fracture toughness were tested of 20CrMnTi steel quenched at different temperatures. The effects of TiN inclusions on the impact toughness and fracture toughness were investigated according to the Hall-Petch relationship. The results show that, TiN inclusions are high temperature stable phases which insoluble to the matrix, mostly squared in shape and dispersed. The impact toughness and fracture toughness of 20CrMnTi steel decrease with increasing sizes of the initial austenite grains, martensite packets and blocks as the quenching temperature increases. Interestingly, the TiN inclusions strongly affect the toughness of the 20CrMnTi steel in the fracture and the fine-grained sample has a better toughness. Under high-stress concentrations, TiN inclusion particles can initiate cleavage cracking.