Effect of Bismuth Element on Hot Ductility of 316L Austenitic Stainless Steel

The hot ductility deformation ability of 316L austenitic stainless steel containing bismuth was investigated by high temperature forging and high temperature tensile test with Gleeble machine.The effect mechanism of bismuth on the hot ductility was analyzed by OM and SEM-EDS.The results show that bismuth element mainly exists in the form of bismuth metal inclusions with micron and nanometer sizes in the experimental steel, which can improve the machinability of the steel.The experimental steel containing bismuth is prone to crack at grain boundaries and has poor plasticity at high temperature during forging and stretching at high temperature.The reduction of area at 850-1000 ℃ is less than 40%.The reason is mainly related to the grain boundary segregation of bismuth.At high temperature, the grain boundary segregated bismuth particles exist in the form of liquid, which can significantly reduce the grain boundary binding force and lead to intergranular brittle fracture.