Effect of Solution Treatment on Microstructure and Mechanical Properties of 2205 Duplex Stainless Steel

摘要

Duplex stainless steels have dual phase microstructure consisting of approximately equal volume fraction of ferrite and austenite. Volume fraction of phases significantly affects mechanical properties of duplex stainless steels. In the present work, effect of solution treatment temperatures (in the range of 900 – 1150 °C) on microstructure (phase % of ferrite and austenite) and mechanical properties like tensile (room temperature (RT)) and Charpy impact (RT and -25 °C) of duplex stainless steel, 2205 were investigated. Analysis indicates that with increase in solution treatment temperature, % ferrite phase increases and % austenite phase decreases. 50 – 50% combination of both phases was obtained around 1020 °C. Tensile test results indicate that yield strength and ultimate tensile strength remains similar for all temperatures. Maximum Charpy strength was obtained at 1050 °C. A sudden drop in charpy strength was observed at 950 °C for both RT and -25 °C tests. Microstructural and SEM analysis reveals the presence of intermetallic phases like sigma (σ) and chi (χ), precipitated at ferrite/ferrite boundary and ferrite/austenite grain boundary which may cause the decrease in impact properties.