Accession Number : AD0670800

Title :   MECHANISM OF SUPERPLASTICITY IN A1-78%ZN ALLOYS.

Descriptive Note : Annual interim summary rept. no. 1, 20 Jun 67-30 Jun 68,

Corporate Author : LOCKHEED-GEORGIA CO MARIETTA MATERIALS SCIENCES LAB

Personal Author(s) : Underwood,Ervin E. ; Fike,F. D. ; Kronzlein,H. H. ; Lee,E. U. ; Rock,H. J.

Report Date : 30 JUN 1968

Pagination or Media Count : 56

Abstract : Superplasticity has been studied in the Al-78%Zn alloy with the purpose of identifying the basic mechanisms that control this unusual process. The experimental investigation has systematically covered the mechanical and microstructural relationships over a range of temperatures and strain rates, for different heat-treatments. Replication, electron microscopy, and selected area diffraction have been combined to relate the prior history of the alloy, its microstructure, and the nature of its defects. Moreover, through cinematography, such mechanisms as grain boundary sliding, grain rotation, and profuse dislocation generation are shown to occur during the actual process of superplasticity. The important experimental observations are discussed, and it is concluded that superplastic deformation in the Al-78%Zn alloy consists of grain boundary sliding, diffusional creep along grain boundaries, and dynamical interactions of dislocation. (Author)

Descriptors :   (*ALUMINUM ALLOYS, MECHANICAL PROPERTIES), (*ZINC ALLOYS, PLASTIC PROPERTIES), HEAT TREATMENT, MICROSTRUCTURE, AGING(MATERIALS), TEMPERATURE, RODS, TENSILE PROPERTIES, ELONGATION, STRAIN HARDENING, DEFORMATION, CREEP, GRAIN STRUCTURES(METALLURGY), INTERACTIONS, ELECTRON MICROSCOPY, PHOTOMICROGRAPHY

Subject Categories : Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE