Effects of Purity and Processing on the Exfoliation Corrosion Behavior of 7X75 Aluminum Plate.
Abstract
The effect of varying iron and silicon content on the exfoliation corrosion behavior of two 7x75 type wrought aluminum alloys was investigated using the ASTM EXCO test. One series of alloy plates (5/8 inch thick) was basically the composition of 7475 with total iron and silicon varying in five steps between 0.03 and 0.31 weight percent. The other series contained Zr in place of Cr in the basic composition, and had a comparable variation in iron and silicon content. Each of the two series was processed both in the standard T651 temper and by a thermomechanical process (TMP). Twenty different combinations of composition and processing were studied this way. Test results showed that, in general, the variation in iron and silicon content had no significant effect on exfoliation resistance in either temper or alloy series. Corrosive attack on the TMP coupons was more uniform than on the T651 coupons. Long subsurface cracks were observed in the T651 coupons. Machined sides of the TMP coupons showed almost no attack, while those of the T651 coupons pitted. The depth of attack was about 1.5 times greater on the rolled surfaces of T651 coupons compared to TMP coupons. End-grain attack depth of T651 coupon sides was three times that of TMP coupon sides. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1975
- Accession Number
- ADA015728
Entities
People
- Peter J. Blau
Organizations
- Air Force Research Laboratory