Regulation of mechanical properties in vanadium-containing high-nitrogen austenitic stainless steel via nano-Sized precipitated phase control

Abstract

Nitride precipitation in high-nitrogen austenitic stainless steels significantly affects the mechanical properties of said steels. In this study, vanadium microalloying was employed to prepare high-nitrogen austenitic stainless steel with excellent comprehensive mechanical performance. The characteristics of the different precipitated phases, precipitation and dissolution behaviors, and their effects on mechanical properties were investigated. The impact mechanism of the precipitated phases on the mechanical properties of stainless steel was also discussed. The results indicate that the Me2X-type precipitated phase in the vanadium-containing high-nitrogen stainless steel exhibits a hexagonal close-packed (HCP) structure, forming a incoherent relationship with the matrix. This leads to a significant reduction in ductility owing to the larger size of particles enriched at the grain boundaries with minimal strengthening effects. Conversely, the MeX-type precipitated phase exhibits a face-centered cubic (FCC) structure, maintaining a semi-coherent relationship with the matrix. This results in smaller particle sizes and a more dispersed distribution, leading to a pronounced strengthening effect without compromising plasticity. Effective control of the precipitated phase can be achieved by solution treatment at different temperatures. Specifically, stainless steel subjected to a 1100 °C solution treatment exhibits only fine, dispersed MeX-type precipitated phases, resulting in optimal comprehensive mechanical properties: yield and ultimate tensile strengths of 587 and 924 MPa, respectively, with an elongation of 55% and a strength-ductility product of 49.6 GPa·%.

Keywords

• High-nitrogen austenitic stainless steel
• Vanadium microalloying
• Precipitation control
• Strength
• Plasticity