Accession Number : ADA137518

Title :   Effects of Fatigue on the G. P. Zones in Al-Zn Alloys.

Descriptive Note : Technical rept.,

Corporate Author : NORTHWESTERN UNIV EVANSTON IL DEPT OF MATERIALS SCIENCE

Personal Author(s) : Pahl,R G , Jr ; Cohen,J B

PDF Url : ADA137518

Report Date : 16 Jan 1984

Pagination or Media Count : 49

Abstract : Small-angle x-ray scattering has been applied to study the evolution and stability of G.P. zones in two Al-Zn alloys during fatigue, to provide statistically sound information on this process. In a 5.3 at pct Zn alloy containing zones with an average diameter of the normally sluggish coarsening was accelerated by fatigue at room temperature. In the same alloy with larger zones there is no growth, except near a fatigue crack. Reverted samples aged rapidly during fatigue at room temperature, but in a reverted sample of Al-3.5 at pct Zn tested, appreciable zone growth did not occur. Upon warming this sample (without any load) to room temperature, rapid clustering took place. These results imply a vacancy fraction produced during fatigue, and this excess vacancy concentration appears to be the cause of zone growth during room temperature fatigue.

Descriptors :   *Aluminum alloys, *Zinc alloys, *Fracture(Mechanics), *Crack propagation, *Fatigue(Mechanics), Zone melting, X ray scattering, Room temperature, Clustering, Phase transformations, Distribution functions, Radius(Measure), Least squares method, Angles, Research management

Subject Categories : Properties of Metals and Alloys
      Statistics and Probability
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE