An investigation of the effects of microstmcture and stress ratio on fatigue crack growth in Ti―6Al―4V with colony α/β microstructures

摘要

This article examines the combined effects of colony microstmcture and stress ratio on long fatigue crack growth in Ti-6Al-4V. The fatigue crack growth rates are compared in lamellar microstructures with fine and coarse lath dimensions produced by controlled cooling (rate) from the β phase field. The effects of β volume fraction are also investigated at stress ratios, R = K_(min)/K_(max), between 0.1 and 0.8. The combined effects of the different variables are then modeled using multiparameter concepts. The coarser lamellar microstructures are shown to have better fatigue crack growth resistance than finer lamellar structures. However, β volume fraction is shown to have only a limited effect on fatigue crack growth resistance. Finally, the implications of the results are discussed for microstructural design and fatigue crack growth prediction.