Microstructure and mechanical properties of a novel cast multi-phase stainless steel
Zixiang Wu, Yuan Liu, Huawei Zhang, Xiang Chen
Abstract
Cast stainless steels with high strength and toughness are very important for industrial production, but the strengthening methods are very limited. In this study, a novel cast multi-phase stainless steel (CMPSS) containing ferrite, martensite and austenite was prepared and its strengthening mechanism was investigated. After solid solution and tempering at 520 °C for 4 h, the yield strength of the sample reaches over 800 MPa, and the total elongation exceeds 13%. This tempering strengthening is mainly achieved by precipitation of the nanoscale Laves phase pinning dislocations in ferrite. However, when prolonging the tempering time or increasing the tempering temperature, the Laves-phase particles precipitate and coarsen along the phase boundary, which seriously damages the strength and toughness of the sample. In addition, high-temperature tempering also leads to a decrease in retained austenite (RA) content by reducing the amount of C and Mn elements in the lath martensite and promotes the precipitation of the R phase (molybdenum-rich intermetallic compound) in ferrite, which is also detrimental to the mechanical properties of CMPSS.