Accession Number : AD0707740

Title :   MECHANISM OF SUPERPLASTICITY IN Al-78%Zn ALLOY.

Descriptive Note : Technical rept. no. 3, 20 Jun 69-20 Jun 70,

Corporate Author : LOCKHEED-GEORGIA CO MARIETTA MATERIALS RESEARCH AND DEVELOPMENT LAB

Personal Author(s) : Underwood,Ervin E. ; Lee,Enu U. ; Kranzlein,Harvard H.

Report Date : 20 JUN 1970

Pagination or Media Count : 32

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)

Descriptors :   (*ALUMINUM, DEFORMATION), (*ZINC ALLOYS, DISLOCATIONS), ALUMINUM ALLOYS, PLASTIC PROPERTIES, HEAT OF ACTIVATION, RECOVERY

Subject Categories : Properties of Metals and Alloys
      Solid State Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE