Precipitation law of σ phase in 2205 duplex stainless steel

After solution treatment at 1300℃ and cold rolling deformation at different reductions, 2205 duplex stainless steel was homogenized at different temperatures for different time intervals. To study the precipitation behavior of σ phase in the steel, the microstructure of specimens was observed by optical microscopy and transmission electron microscopy, and the volume fraction of σ phase in the microstructure was calculated by Image Tool software. The results show that when the steel is homogenized at 950℃, the precipitation time of σ phase is shortened from 30min to 3 rain with the increase of cold rolling reduction from 50% to 85%. As to specimens with a cold rolling reduction of 85%, the volume fraction of σ phase increases from 1.2% to 11.8% when the homogenizing time is prolonged from 3 min to 30 min at 950℃ However, after homogenization for 5 min, the volume fraction of σ phase decreases from 8.9% to 3.6% with the rise of temperature from 875 to 950℃; moreover, when the homogenizing temperature is 975℃, No phase exists in the specimen.