Fatigue Resistant Aluminum P/M Alloy Development.
Abstract
An investigation was undertaken to study the effects of fabrication practice, alloy chemistry, aging treatment, and residual stress relief on the fatigue crack growth (FCG) resistance of 7XXX P/M hand forgings and extrusions. Testing was performed in both humid air (R.H.>90%) and salt fog atmosphere. FCG rates of the P/M extrusions were slightly higher than those of a 7050-T76511 control material at delta k values below 4 MPa-square root of m. From 4-10 MPa-square root of M, FCG resistance of the P/M extrusions were approximately equivalent to those of the 7050 control. Overaging was beneficial to the FCG resistance of the P/M extrusions. Scatter in the FCG data for the hand forgings prevented any definite conclusions regarding effects of chemistry of aging treatment on crack growth in these materials. FCG testing of stress-relieved and nonstress-relieved forgings showed that compressive residual stresses can markedly affect effective delta K levels and measured FCG rates. The introduction of crack closure concepts to the data analysis allowed for a computation of effective delta K values to correct for the presence of residual stresses in FCG specimens. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1979
- Accession Number
- ADA081949
Entities
People
- R. E. Sanders Jr.
- R. J. Bucci
- W. L. Otto Jr.
Organizations
- Alcoa