Abstract: The low temperature fracture mechanism of high manganese austenitic steels is studied. High manganese steels undergo a ductile-to-brittle transition at low temperature, which is accompanied by a change in the fracture mechanism from dimple fracture to intergranular fracture. During the fast cooling process of solution treatment, nonequilibrium segregation of manganese was produced at austenite grain boundaries. Due to the strength, strain hardening exponent and strain hardening rate of manganese segregation zone are higher than that of matrix, therefore, dislocations pile up at the segregation zone and produce higher internal stress during loading and deformation. Since the stress at the segregation gone are much greater than that of matrix, thus, the high stress causes intergranular fracture at grain boundary segregation zone.

Key words: Cryogenic steels, High manganese austenitic steels, Intergranular fracture, Nonequilibrium segregation