The Kinetic diagram of sigma phase and its precipitation hardening effect on 15Cr-2Ni duplex stainless steel

The kinetics of sigma phase precipitation at the temperature range of 750-950 °C in a rapidly solidified 15Cr-2Ni-2Al-11Mn resource-saving duplex stainless steel was investigated. After fitting the experimental results with the Avrami equation, the TTT diagram of sigma phase was established. It is found that the precipitation rate of sigma phase maximizes at about 850 °C and that the precipitation hardening effect sharply peaks at about 1.5 vol% sigma phase content, which is obtained by aging at 850 °C for 180 min. With the further increase of sigma phase content from 1.5 vol%, the strength reduces and the ductility increases again.