MECHANISM OF SUPERPLASTICITY IN Al-78%Zn ALLOY.
Abstract
Activation energies were obtained for dynamic recovery and for tensile deformation. The values for deformation are delta H sub d = 22.5 plus or minus 3.5 kcal/mol (at low temperatures) and delta H sub d = 37.5 plus or minus 2.5 kcal/mol (at high temperatures). These two activation energies are related to the rate-controlling processes of cross-slip and dislocation climb, respectively. Thus, the activation energy for dynamic recovery, delta H sub r = 22 kcal/mol, corresponds to the cross-slip of screw dislocations, which leads to the formation of stable dislocation networks and dislocation-free sub-grains. At higher deformation temperatures, dislocation climb predominates, and subboundary disintegration and coalescence of subgrains are observed. Dislocation loops have been reported mostly in fcc metals and alloys after quenching from elevated temperatures and subsequent aging. This paper reports the formation and characteristics of dislocation loops in the hcp Zn-0.7%Al alloy resulting from quenching and aging. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 20, 1970
- Accession Number
- AD0707740
Entities
People
- Enu U. Lee
- Ervin E. Underwood
- Harvard H. Kranzlein
Organizations
- Lockheed Martin