Assessment of 3D Short Crack Closure in Ti-6Al-4V Alloy Utilizing Synchrotron X-ray Microtomography

Abstract

Synchrotron X-ray microtomography was utilized to observe the complex 3D crack morphology and the closure behavior of a short crack in Ti-6Al-4V alloy. The aim of the study was to investigate the effect of the crack path evolution on the 3D short crack closure behavior. In situ fatigue tests at R = 0.1 were carried out using microtomography with a spatial resolution of 1 μm. The 3D crack morphology was observed in detail consisting of non-facets (zigzag), branching, and facets with deflection angles indicating the presence of mode II and mode III displacements. The crack grows with facet-like paths mainly in α grains as compared to the non-facet paths in the α+β grains. The change in the crack path from facet-like paths to non-facet-like paths in the larger crack front induces an increase in the fractional area of closed patches.