In-situ study of martensitic transformation and nucleation, propagation ofcrack in CuNiAl shape memory alloy

The stress-induced martensitic transformation and its relation with crack n ucleation and propagation in CuNiAl shape memory alloy were investigated th rough in-situ tensile tests by SEM and TEM. The results indicated that the stress concentration ahead of the crack tip could induce formation of stack ing faults and different types of martensites. TEM observations showed that the martensites could transform from one type to another and even reversel y to the parent during loading. The microcracks nucleated along the martens ite/parent interface and intersection between two martensites. When, the cr ack propagated a certain distance, the stress concentration ahead of the cr ack tip was large enough to result in formation of slip bands, and in this condition the microcrack nucleated along slip bands more easily.