A STUDY OF FATIGUE CRACK INITIATION IN A TWO PHASE β-METASTABLE TITANIUM ALLOY

α/β titanium alloys are choice materials for aeronautical and automotive industries due to their high performance to density ratio. For several applications, fatigue resistance is one of the critical design parameter. Particularly, initiation of fatigue crack plays a key role. Furthermore, hardly anything can be found in the literature on the fatigue crack initiation in multiphase microstructures. This work deals with the characterisation of the high cycle fatigue crack initiation in the TIMETAL LCB α/β titanium alloy. Microstructure was characterised by SEM, XRD, EBSD and TEM. Fatigue tests were carried out on a microstructure presenting a finely grained and equiaxed α/β morphology. Observations of the crack initiation were conducted at the scale of the microstructure thanks to SEM. Orientation Image Microscopy (OIM) allowed to correlate microstructural and micromechanical aspects