Effect of Defects in Aluminum P/M
Abstract
No previous work on the first generation P/M aluminum alloys studied whether foreign contaminants were limiting the potential of these materials. The present program conducted fatigue tests on a forging, an extrusion, and an as- compacted billet of the CT 91 (formerly MA 87) composition. Specimens taken from both the L and L-T orientations were tested with fatigue lives between 1,000 and 1,000,000 cycles. Specimens with abnormally short or unusually long fatigue lives were fractographically examined and compared with typical failures. No obvious differences were noted among the three types of failures, although several types of defects were characterized at the initiation sites. These include (1) alumina inclusions (approx. 60 percent occurrence), (2) transition metal inclusions (approx. 30 percent occurrence), and (3) microstructural boundaries (approx. 10 percent occurrence). The fatigue strength at 10,000,000 cycles was also measured for specimens with a theoretical stress concentration factor, K(t) of three and ten. The milder notched specimens, K(t) = 3, had a 70 percent greater fatigue strength than that measured for high strength ingot alloys. The K(t) = 10 fatigue strength is the same as that measured for 7000 series ingot alloys.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1981
- Accession Number
- ADA113134
Entities
People
- J. S. Santner
Organizations
- Materials Research Laboratory