Aluminum-Lithium Alloy Research.
Abstract
A recent Air Force program was focused on developing an isotropic aluminum-lithium alloy, having greater than two weight percent lithium. The addition of two weight percent lithium can reduce the density of aluminum by six percent and increase the modulus by twelve percent, thus offering significant benefits for weight savings in aerospace systems. The Air Force program was successful in that the difference between the longitudinal and 45 degree yield strengths of the experimental alloy was significantly reduced over that previously observed for alloys containing greater than two weight percent lithium, i.e., only a 10% variation compared with 20-25% for commercially available alloys. The alloy, designated AF/C-498 has the composition of Al-2.7Cu-2.1 Li-0.6Zn.0.3Mn-0.3Mg-0.5Zr and the standard aging treatment was to solution heat treatment, quench, stretch 6% and age for 24 hours at 150 degrees C. Unfortunately the elongation after this aging treatment is lower than the minimum of five percent that is desirable for aerospace applications. The research under this contract was concerned with examining aging treatments that would improve the elongation with no sacrifice in strength or isotropic properties. The material studied was received from the Air Force Materials as 0.5 inch plate. The plate was marked that it had been solutionized at 540 degrees C, quenches, stretched 6%, and aged at 300 degrees F (149 degrees C) for 24 hours (T8).
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1997
- Accession Number
- ADA365347
Entities
People
- A. A. Csontos
- E. A. Starke Jr.