Influence of amorphous phase on crack initiation and propagation behaviours in NiTi shape memory alloy based on extended finite element simulation

Local amorphous phases often appear in NiTi shape memory alloys (SMAs) which undergo a large degree of cold plastic deformation. Fracture damage is a common failure mode of NiTi SMAs in engineering application and it is usually caused by the crack initiation and propagation. The crack initiation and propagation behaviours in NiTi SMA parts containing amorphous phases have not been reported so far. In the present study, extended finite elements method (XFEM) was applied to investigate the influence of amorphous phase on crack initiation and propagation behaviours in a notched NiTi SMA specimen processed by cold plastic deformation. The results show that the amorphous zone has a significant influence on both the crack initiation and the crack propagation. Crack is easier induced if there exists amorphous phase in the NiTi SMA but it is difficult for the crack to pass through the amorphous zone.