Titanium alloy fatigue fracture facet investigation by selected area electron channeling

Flat regions (facets) found on fracture surfaces caused by initiation and propagation of fatigue cracks through the titanium alloys IMI-685 tested with and without a 5 min load dwell and Ti-11 have been examined using selected area electron channeling. The crystallographic planes of the facets have been identified as being near basal for the IMI-685 and more random for the Ti-11. None of the dwell specimens showed a pure basal facet orientation. The plastic zone size was also assessed and found to correlate approximately with stress intensity, allowing confirmation of crack initiation sites as determined by fractography. One case of beta to alpha-beta transformation crystallography is also examined. A partial channeling map for titanium is presented.