Effect of notch root radius on apparent fracture toughness of Ti6Al4V alloy: experiments and simulations

Ti6Al4V is a widely used titanium alloy known for its excellent combination of mechanical properties, corrosion resistance, and biocompatibility. However, to ensure its effectiveness in various applications, it is important to understand the mechanical and fracture behavior of the alloy in the presence of a notch. In the present study, the effect of notch root radius on mode I fracture toughness of Ti6Al4V alloys with a nearly bimodal microstructure has been investigated. Fracture toughness tests were conducted on compact tension (CT) specimens with five different notch root radii. The experimental results demonstrate that the apparent fracture toughness, \(K_{IA}\), increases linearly with the square root of the notch root radius. Further to elucidate the results, a 2D elastoplastic finite element analysis is performed on the CT specimens using cohesive zone model. The simulation results are in good agreement with the experimental data. The study also reveals that the apparent fracture toughness is independent of the notch root radius below a critical value, estimated to be approximately \(50\ \mu m\). Finally, the scanning electron microscopy of the fracture surfaces has been examined. The micrographs reveal void coalescence and dimple regions indicating the ductile nature of the fracture process.