用原子力显微镜研究形状记忆合金中裂纹形核和扩展

运用原子力显微镜（AFM）对形状记忆合金CuNiAl中裂纹扩展行为进行了观察。观察表明、拉伸时、裂纹尖端首先产生马氏体。纳米微裂纹择优沿马氏体相界面形核。但当外力较大，且裂纹扩展距离较长使裂尖应力集中足够大时，不但能诱发马氏体相变。也可出现滑移带。一旦出现滑移带，裂纹也可沿马氏体或滑移带交替扩展。

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.