The relationship between fracture mechanism and substructures of primary M7C3 under the hot compression process of self-healing hypereutectic high chromium cast iron

Abstract

Hypereutectic high chromium cast iron (HHCCI) possesses excellent thermal deformation potential, although it is difficult to deform at room temperature. It can release stress through the fracture of primary M7C3 (P-M), and the softened eutectic structure has a self-healing effect on the cracks to ensure the continuity of material. The morphology of the P-M is very irregular, with the distinct relative dimensions between P-MH ((001) plane//compression plane) and P-ML ((100) or (110) plane//compression plane). From TEM and SEM characterizations, the crack propagation site of P-ML is consistent with the interface of internal multidirectional stacking faults. The fractures of P-ML extend along the (100) (or (110)) and (001) planes during room-temperature and hot compression, respectively. This difference is contributed to the change of the stress state of P-ML by softened austenite and the improvement of the deformation ability of P-M itself. In addition, the anisotropic hardness and strain hardening behavior of P-ML and P-MH were also contributed to the anisotropy of internal stacking faults.