Observations on the Role of Hydrogen in Facet Formation in Near-alpha Titanium (Preprint)
AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS & MANUFACTURING DIR METALS CERAMICS & NONDESTRUCTIVE EVALUATION DIV/NONDESTRUCTIVE EVALUATION BRANCH
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Faceted features are frequently observed on the fracture surfaces of titanium alloys that have failed by static loading, continuous cycling, dwell fatigue loading, and stress corrosion cracking. Although the facets formed under different loading conditions appear qualitatively similar, there are significant differences in the spatial and crystallographic orientations of the facets as well as subtle differences in facet surface topography. The present study compares and contrasts facets in the Ti-8Al-1Mo-1V alloy with the primary motivation being to understand the mechanisms of crack initiation and faceted growth during dwell fatigue. The spatial and crystallographic orientations of the facets were determined using quantitative tilt fractography and electron backscatter diffraction while facet topography was examined using ultra high resolution scanning electron microscopy. Collectively, these observations suggest that hydrogen plays an important role in facet formation and accelerating small crack growth rates during dwell fatigue loading.
- Inorganic Chemistry