Variation in retained austenite content and mechanical properties of 0.2C-7Mn steel after intercritical annealing

摘要

The effects of annealing time and temperature on the retained austenite content and mechanical properties of 0.2C-7Mn steel were studied. The retained austenite content of 0.2C-7Mn steel was compared with that of 0.2C-5Mn steel. It is found that 0.2C-7Mn steel exhibits a similar variation trend of retained austenite content as 0.2C-5Mn steel. However, in detail, these trends are different. 0.2C-7Mn steel contains approximately 7.5vol% retained austenite after austenitization and quenching. The stability of the reversed austenite in 0.2C-7Mn steel is lower than that in 0.2C-5Mn steel; in contrast, the equilibrium reversed austenite fraction of 0.2C-7Mn steel is substantially greater than that of 0.2C-5Mn steel. Therefore, the retained austenite content in 0.2C-7Mn steel reaches 53.1vol%. The tensile results show that long annealing time and high annealing temperature may not favor the enhancement of mechanical properties of 0.2C-7Mn steel. The effect of retained austenite on the tensile strength of the steel depends on the content of retained austenite; in contrast, the 0.2% yield strength linearly decreases with increasing retained austenite content.