Study on the HCF Fractograph of TC17 Titanium Alloy with Equiaxed and Basket-waved Microstructure

Abstract:

In this article, the effect of two typical microstructures (equiaxed and basket-waved microstructure) on the fracture morphylogy of high cycle fatigue is investigated. The results show that the macro-fracture surface of the samples with both microstructures is charactered by brittle fracture and the fatigue crack initiates at the sample surface. The difference of the fractograph between the two microstructures is significant. On macro level, fractograph of equiaxed microstructure is quite smooth, and the fatigue crack area has a very large fraction of the whole facture surface. While fractograph of basket-waved microstructure is rough, and the fraction of fatigue crack area is relatively small. On micro level, the fatigue striation in equiaxed microstructure has a similar size with the primary α grain. While in basket-waved microstructure, basket-waved structure can be clearly seen in the fatigue fracture surface. Secondary cracks are more pervasive than in equiaxed microstructure. The fatigue striation also has a different morphylogy with than in equiaxed microstructure.

Key words:TC17 titanium alloy; Equiaxed microstructure; Basket-waved microstructure; Fatigue fractography