The effect of volume fraction of primary a phase on fracture toughness behaviour of Timetal 834 titanium alloy under mode I and mixed mode I/III loading

摘要

The effect of volume fraction of primary α phase on mode I and mixed mode I/III fracture toughness of Timetal 834 titanium alloy was investigated. The mode I and mixed mode I/III fracture toughness values for loading angle of 30 were found to initially decrease and subsequently increase with increase in volume fraction of primary a phase. On the other hand, mixed mode I/III fracture toughness for loading angle of 45° was found to monotonically decrease with increasing volume fraction of a phase. The fracture toughness was also found to marginally increase with increasing loading angle for the two lower primary a volume fractions, i.e. 6% and 15% whereas it marginally decreases with increasing loading angle for primary a volume fraction of 30%. The results were explained on the basis of the nature of stress field ahead of the crack tip under mixed mode I/III loading as well as the fracture mechanisms operative in this alloy for different a volume fractions.