Effect of Thermo-mechanical Treatment on the Formation Behavior of Martensite in 316L Stainless Steel

Abstract

This study was carried out to investigate the effect of thermo-mechanical treatment on the formation behavior of martensite in 316L stainless steel. Dislocation, alpha' and epsilon-martensite were formed by thermo-mechanical treatment. Martensite with surface relief and specific direction was formed by thermo-mechanical treatment. Martensite formed by thermo-mechanical treatment were reversed to austenite with an ultra-fine grain size of less than 1 pm by annealing treatment at 700 degrees C for 20 min. alpha'-martensite with a K-S orientation relationship and e-martensite with a [110]gamma vertical bar vertical bar [100]epsilon orientation relationship to the matrix was formed by thermo-mechanical treatment. The volume fraction of dislocation, alpha' and epsilon-martensite were increased with the cycle number of thermo-mechanical treatment. In 5-cycle number thermo-mechanical treated specimens, more than 25% of the volume fraction of alpha'-martensite and less than 5% of the volume fraction of epsilon-martensite were attained. The austenite grains were fairly deformed by thermo-mechanical treatment and the grain size of austenite with various orientation relationship were changed from micrometer to sub-micrometer by the 5-cycle thermo-mechanical treatment.