H. W. Babel, C. J. Parrish, K. K. Sankaran, The Boeing Company, Huntington Beach, CA

Summary:

This presentation will describe the status of the third generation aluminum-lithium alloys (e.g. 2099), which appear to have overcome the difficulties such as the anisotropy of mechanical properties and low toughness associated with the earlier alloys (e.g. 2090 and 8090). Despite reducing the lithium content of the 3^rd generation alloys to less than 2%, the weight benefits achievable are still significant to warrant their selection and production use in aerospace products.

The manufacturing and design issues encountered with the 2^nd generation Al-Li alloys will be described along with several successful flight experiences, a number of which have not been previously presented publicly. The status of the 3^rd generation alloys are compared to the issues encountered with the 2^nd generation alloys, and the extent to which these issues have been resolved or mitigated will be presented. The current status relative to design databases and those scheduled to appear in MMPDS (formerly MIL-HDBK-5) and AMS specifications for the 3^rd generation alloys will be provided. The current and future potential applications in the public domain will be described for future aircraft and aerospace applications.

It is concluded that Al-Li alloys are suitable for selected applications wherein the higher initial and often the manufacturing costs of these alloys can be offset by the resulting weight benefits. For aircraft applications, the exceptional fatigue properties are often a major consideration. The special characteristics of Al-Li alloys still need to be considered in design and manufacturing of the third generation alloys.