TOUGHNESS AND MICROSTRUCTURAL FACTOR OF Ti-6Al-4V ALLOY.

Instrumented Charpy impact test, dynamic fracture toughness test and static fracture toughness test by the DC electrical potential method were carried out on Ti-6Al-4V alloys with various microstructures to investigate the effect of microstructural factors including fractographic measurements on various toughness criteria, i. e. , Charpy absorbed energy (E//t: total absorbed energy, E//i: apparent crack initiation energy, E//p: apparent crack propagation energy), dynamic fracture toughness (J//d), static fracture toughness (J//I//C or K//Q), static crack propagation resistance curve (J//R curve), and static tearing modulus (T//m//a//t). Evaluated toughness of Ti-6Al-4V alloy appeared different between the Charpy test and the dynamic toughness test mainly because the microstructural unit which controls the fracture may be different between these tests. Evaluated toughness by J//R curve or T//m//a//t did not necessarily coincide with that by J//I//C. Thus, it is necessary to use a proper toughness criterion according to the method of design. It was found that microstructure had a more significant role in influencing the T//m//a//t rather than J//I//C.