含Cu马氏体时效不锈钢的组织与强韧性

An increase in strength often leads to a decrease in the ductility and toughness of maraging stainless steels; this phenomenon is known as the strength-ductility/toughness trade-off dilemma in structural materials. Some studies have found that the introduction of submicro/nanometer-sized retained or reverted austenite could mitigate the strength-ductility/toughness trade-off of high-strength maraging stainless steels. In this work, a novel strategy to accelerate austenite reversion by Cu addition in a Fe-Ni-Mo-Co-Cr maraging stainless steel was studied. In addition, the aging behavior and its effects on the mechanical properties of a Cu-containing Fe-Cr-Co-Ni-Mo maraging stainless steel were systematically studied. Transmission electron microscope characterizations showed that Cu- and Mo-rich phases precipitated from the steel matrix in sequence during the aging process; more specifically, a part of Mo-rich phase nucleated at the Cu-rich phase and then grew. Moreover, along with the segregation of Cu and Ni, reverted austenite was formed gradually. With an increase in the aging time, the stability of the reverted austenite increased, resulting in a substantial increase in its toughness. After aging for 90 h, the yield and tensile strengths of the steel reached 1270 and 1495 MPa, respectively, and the impact energy and fracture toughness were 81 J and 102 MPa·m^1/2, respectively, showing an excellent match of strength and toughness compared with commercial maraging stainless steels.