Abstract: Lateral surface near the fracture of tensile sample was examined by scanning electron microscopy (SEM) before and after oxide film removing. The relationship between surface morphology and microstructure was established. The results show that the microcracks are caused by brittleness rupture of surface oxide films due to α lamellas sliding along α lamella boundaries. And the sliding of aligned α lamellas bring not only microcrack formation but also the raise of colony relative to prior sample surface. A slip model, which depicts the relationship between surface morphology and microstructure, was brought forward to analyze the observation.

Key words: Titanium alloy, Sliding, Crack