AFM observation of crack propagation in CuNiAl shape memory alloy

The nucleation and propagation behaviors of cracks in CuNiAl shape memory alloy were observed using atom force microscopy (AFM). The results indicate that the martensite firstly formed at crack tip, the microcrack in nanometer is preferential to nucleate along martensite interface upon loading. When the external load was relatively big, the crack relatively long, thus the concentrated stress big enough, not only the martensite transformation, but also the slip bands are induced. Once the slip bands formed, the crack will propagate along martensite and slip bands alternatively.