Improved Mechanical Property and Corrosion Resistance of SAF2507 Duplex Stainless Steel with Heterogeneous Lamella Structure

Severe cold rolling and subsequent annealing are implemented on ferrite and austenite duplex stainless steel (DSS). The microstructure and mechanical properties of the processed sample are investigated systematically. The results show that the heterogeneous lamella (HL) structure can be generated in the cold-rolled DSS by an appropriate annealing strategy. After annealing at 900 degrees C for 2 min, the HL-structured sample with an alternative distribution of micrograined lamellae in ferrite and ultrafine-grained lamellae in austenite obtains a unique combination of high strength and good ductility; the corresponding yield strength and uniform tensile elongation are approximate to 730 MPa and approximate to 23%, respectively. In addition, the corrosion behavior of the DSS in different processing states is investigated by the electrochemical method. The HL-structured DSS possesses a superior corrosion resistance compared with other counterparts, which is attributed to the formation of a more stable passive layer on the surface. The precipitation of the sigma phase after long-term annealing leads to deterioration of corrosion performance and mechanical properties.