High cycle fatigue and fracture behavior of Ti-5Al-5Mo-5V-3Cr alloy with BASCA and double aging treatments

The fatigue performance of the newly developed Ti-5Al-5Mo-5V-3Cr alloy for aerospace applications in two microstructural conditions was investigated, as well as the fracture surfaces obtained after fatigue tests. High cycle fatigue was assessed based on the standardized staircase method and the corresponding Dixon-Mood statistics. The fatigue limit exhibited an improved result for the microstructure presenting a harder matrix due to the finer and more homogeneous distribution of α phase. Crack nucleation, whether at the surface or subsurface, could be associated to the thickness of the α phase film at grain boundaries. Typical fatigue striations were only found in the basket-weave structure. Unstable crack growth happened in transgranular mode and presented a mixture of cleavage facets and dimpled areas independently of the α phase distribution inside the primary grains.