Microstructure and Strength-Toughness of a Cu-Contained Maraging Stainless Steel
An increase in strength often leads to a decrease in the ductility and toughness of mar-aging 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 re-tained or reverted austenite could mitigate the strength-ductility/toughness trade-off of high-strength mar-aging 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 systemati-cally 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 re-verted 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·m1/2,respectively,showing an excellent match of strength and toughness compared with commercial maraging stainless steels.
maraging stainless steelreverted austeniteTRIP effectstrength and toughness
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