Dynamic modulus measurements are used to study precipitation rates in 2024 Al alloy. The results are discussed in terms of the effect of structural changes on the elastic modulus as well as the kinetics of precipitation at various stages of the age-hardening process. Activation energies were determined for aging in the temperature ranges from room (77 F) to 130 F, and 375 F to 425 F. A value of 20.7 kcal/gm mole was obtained for the lower temperature range, and 23 kcal/gm mole for the higher temperatures. The data indicate that modulus changes are primarily influenced by the structure of the second phase, however, some evidence of strain energy effects are indicated. (Author)

Technical reports published by the Air Force Materials Laboratoy during the period 1 July 1962 - 30 June 1963 are abstracted herein. Reports on reseqrch conducted by the Air Force Materials Laboratory personnel as well as that conducted on contract are included. These reports cover basic and applied research in the materials area being conducted by the Metals and Ceramics Division, Non-metallic Materials Division, Materials Physics Division, Manufacturing Technology Division, and Materials Applications Division of the Air Force Materials Laboratory.