Abstract

Synchrotron X-ray microtomography was utilized to observe 3D crack closure in bimodal Ti-6Al-4V alloy. The aim of the study is to locallyinvestigate 3D short crack closure behavior. In situ computed tomography of the specimen under fatigue tests at R=0.1 was done at a resolution of 1μm. The reconstruction of the crack images and volume rendering have made it possible to observe crack morphology in detail consisting of facets and non-facet (zigzag) paths indicating the presence of mode II and mode III displacements. The crack grows with a facet-like path in α grains as opposed to the non-facet path seen where the crack grows in the α+β grains. The crack sections with facet paths have lower crack opening levels in comparison to non-faceted crack paths. This shows that a facet-like crack grows in mode II and III shear rather than mode I opening which is dominant in the non-facet cracks.