Analysis of microfracture mechanism of titanium alloy by acoustic emission technique

Microfracture mechanism in fracture toughness test of Ti-8Al-1Mo-1V alloy was examined by the newly developed AE wave analysis system termed dynamic crack microscopy (DCM). The specimen with acicular alpha microstructure had higher fracture toughness than that with equiaxed alpha microstructure, In the acicular alpha 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 alpha microstructure, many microcracks of 110 similar to 370 mu m were nucleated in mixed mode ahead of the crack lip, 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 alpha microstructure.