Effect of Thermomechanical Processing on the Microstructure and Mechanical Properties of a Duplex Stainless Steel

Duplex stainless steels (DSSS) have a microstructure composed of ferrite and austenite phases that gives them a very good combination of mechanical and corrosion properties. These steels are desirable for many applications in the chemical and petrochemical industries. In the present study, a type of stainless steel was cast, solution annealed at ۱۲۰۰°C for ۶۰ min and then quenched in water. Initial microstructure was composed of about ۵۱.۸% ferrite and ۴۸.۱% austenite. The steel was then cold rolled about ۹۰% and subsequent annealing at ۸۰۰,۸۵۰ and ۹۰۰°C for different time were performed. Results showed that tensile strength of steel have been significantly improved. Austenite grain size of cast steel was refined through static recrystallization of the austenite occurred during post cold deformation annealing. Results show that yield strength of as-cast steel is increased from ۵۵۲ to ۱۸۰۰ and its tensile strength increased from ۶۷۲ to ۲۳۵۰ MPa as a result of large cold deformation. With increasing annealing time, sigma phase increases and this leads to decrease of elongation. Thus sigma phase can be expected to embitter the alloy.

Keywords:

Duplex stainless steel , Thermomechanical processing , Microstructure , mechanical properties