Accession Number : AD0725864

Title :   Mechanism of Superplasticity in Al-78 Percent Zn Alloy.

Descriptive Note : Summary technical rept., 20 Jun 67-30 Jun 71,

Corporate Author : LOCKHEED-GEORGIA CO MARIETTA

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

Report Date : 30 JUN 1971

Pagination or Media Count : 88

Abstract : Superplasticity in the Al-78% Zn eutectoid alloy requires a fine-grain, equiaxed microstructure, deformation at temperatures just below the eutectoid temperature, and a strain rate of approximately 0.2/min. An extremely large amount of neck-free elongation is obtained without significant grain growth or change in grain shape. The primary deformation mechanism is attributed to grain sliding and grain rotation at phase boundaries in conjunction with crystallographic deformation and dynamic recovery. A diffusion-controlled accommodation process must operate to preserve the fit at phase boundaries. These conclusions are based largely on our experimental observations, as well as on recent reports in the literature that tend to support this view. (Author)

Descriptors :   (*ALUMINUM ALLOYS, PLASTIC PROPERTIES), (*ZINC ALLOYS, PLASTIC PROPERTIES), GRAIN STRUCTURES(METALLURGY), EUTECTICS, MICROSTRUCTURE, DEFORMATION, DIFFUSION, CRYSTAL DEFECTS, ELECTRON MICROSCOPY

Subject Categories : Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE