Corrosion-Fatigue Crack Propagation Rates in Commercial 7075 and P/M X7091 Aluminum Alloys

Download or read book Corrosion-Fatigue Crack Propagation Rates in Commercial 7075 and P/M X7091 Aluminum Alloys written by M. Kumar and published by . This book was released on 1983 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: The recently developed powder metallurgy (P/M) alloy X7091 (formerly CT91) has strength characteristics similar to ingot metallurgy (I/M) 7000 series alloys. However, its stress corrosion cracking resistance has been reported to be far superior to the conventional ingot-processed alloys. This suggests that P/M alloy X7091 may have far better corrosion fatigue behavior than I/M 7075-T651. Fatigue crack growth rates between 2.5 x 10-8 and 2.5 x 10-6 m/cycle (10-6 and 10-4 in./cycle) were measured for specimens in both the S-T and T-L orientations. In order to determine the effect of environment on the fatigue crack growth rates, tests were conducted in both an innocuous and an aggressive environment (R = 0.5; f = 0.2 Hz). Since it is known that the fatigue crack growth rates of aluminum alloys are sensitive to small amounts of water vapor, gaseous nitrogen with a dew point of -60°C (-75°F) was chosen as the innocuous environment. An aerated 31⁄2% NaCl solution was used as the corrosive environment.