Analysis of microfracture mechanism of titanium alloy by acoustic emission technique

Microfracture mechanism in fracture toughness test of Ti8Al1Mo1V alloy was examined by the newly developed AE wave analysis system termed dynamic crack microscopy (DCM). The specimen with acicular α microstructure had higher fracture toughness than that with equiaxed α microstructure. In the acicular α microstructure, there were many AE events corresponding to the generation of microcracks before the final fracture. AE source characterization indicated that in the case of acicular α microstructure, many microcracks of 110 ∼ 370 μm were nucleated in mixed mode ahead of the crack tip, and main crack extended by coalescence of these microcracks in shear mode. From these results, fracture toughness was evaluated quantitatively, using ductile fracture criterion, and it was found that the colony size had a significant influence on the fracture toughness of the acicular α microstructure.