Effect of microstructure on fracture toughness and fatigue crack growth behavior of Ti17 alloy

Abstract

Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti17) is used extensively in turbine engines, where fracture toughness and fatigue crack growth (FCG) resistance are important properties. However, most research on the alloy was mainly focused on deformation behavior and microstructural evolution, and there have been few studies to examine the effect of microstructure on the properties. Accordingly, the present work studied the influences of the microstructure types (bimodal and lamellar) on the mechanical properties of Ti17 alloy, including fracture toughness, FCG resistance and tensile property. In addition, the fracture modes associated with different microstructures were also analyzed via the observation of the fracture surface. The results found that the lamellar microstructure had a much higher fracture toughness and superior resistance to FCG. These results were discussed in terms of the tortuous crack path and the intrinsic microstructural contributions.