Investigation to Develop a High Strength Stress-Corrosion Resistant Aluminum Aircraft Alloy.

摘要

The objective of the program was to develop a high-strength aluminum alloy resistant to stress-corrosion cracking in the critical short-transverse direction. The alloys investigated include a 7175 control and Al-Zn-Mg-Cu alloys containing 5.8 to 7.4% Zn, 2.0 to 2.5% Mg, and 2.1 to 2.7% Cu along with either separate or combined additions of Zr, Mn, and Cr. They were fabricated from large ingots to two-inch thick plate to insure that the structures would be representative of thick, hot-worked products. All of the experimental alloys developed more attractive combinations of strength and hardenability than the 7175 control along with promising resistance to stress-corrosion cracking. Moreover, most of them developed short-transverse elongation values equal to or higher than that of 7175 on an equivalent strength basis after solution heat treatment times long enough to dissolve substantially all of the Al2CuMg particles. Alloys which contained 5.75-6.75% Zn, 2.0-2.5% Mg, 2.1-2.6% Cu, .09-.15% Zr, .12% max. Fe, and .10% max. Si developed the most attractive combination of properties. (Author)