Nominal vs Local Shot-Peening Effects on Fatigue Lifetime in Ti-6Al-2Sn-4Zr-6Mo at Elevated Temperature
Abstract
A study is presented of elevated temperature fatigue lifetime variability in the shot-peened condition of the titanium alloy, Ti-6Al-2Sn-4Zr-6Mo. It is shown that failures separate into two distributions: (1) governed by the nominal residual stress (RS) profile, promoting subsurface crack initiation and longer lifetimes; and (2) life-limiting behavior that is controlled by localized material-shot-peening interaction. In the residual-stress-free condition, failures occurred predominantly by surface crack initiation at the microstructural scale, by crystallographic facet formation in one or a few a particles or colonies. This mechanism was mitigated under the nominal shot-peening (SP) RS profile, producing failures initiating from the subsurface region by crystallographic faceting spread over a significantly larger area than in the absence of RS. Although the microstructure-scale surface-crack initiation was suppressed, the life-limiting failures under SP continued to occur by surface initiation. but through an apparently larger crack initiation size by formation of a flat, noncrystallographic fracture.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 2009
- Accession Number
- ADA523393
Entities
People
- James M. Larsen
- R. John
- Sushant K. Jha
Organizations
- Air Force Research Laboratory