Characterization of Fatigue Crack-Inititation Facets in Relation to Lifetime Variablility in Ti-6Al-4V (Preprint)
Abstract
An analysis of fatigue crack-initiation facets from the perspective of variability in lifetime of a duplex microstructure of Ti-6Al-4V is presented. Fatigue variability behavior of this alloy was marked by an increase in the lifetime variability to almost three orders in magnitude as the stress level was decreased. Crack initiation was found to occur primarily from the specimen surface with only a few exceptions where subsurface initiation was recorded. In most cases, and irrespective of lifetime, crack initiation was accompanied by crystallographic facet formation across primary- particles. Crystallographic characterization of faceted grains and their neighborhood was conducted by sectioning across the facets using either Focused Ion Beam or mechanical polishing, and subsequent Electron Back Scattered Diffraction analysis of the sections. The emphasis in this study was on discerning the factors that distinguish the crack-initiating microstructural arrangements and plausible mechanisms producing a life-limiting failure versus a long lifetime failure under nominally similar microstructure and applied stress level.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 2011
- Accession Number
- ADA548462
Entities
People
- Christopher Szczepanski
- Patrick Golden
- Reji John
- Sushant Jha
- William Porter Iii
Organizations
- Air Force Research Laboratory