Accession Number:

AD0813396

Title:

STUDY OF STRESS-CORROSION CRACKING OF ALUMINUM ALLOYS

Descriptive Note:

Final rept. 6 Apr 1966-5 Apr 1967

Corporate Author:

ROCKETDYNE CANOGA PARK CA RESEARCH DIV

Personal Author(s):

• Jacobs, A. J.

Report Date:

1967-05-01

Pagination or Media Count:

70.0

Abstract:

A further clarification of the mechanism of stress-corrosion cracking in 7075 aluminum alloy was obtained, particularly with regard to the role of dislocations in the mechanism and to the relationship between dislocation mobility and susceptibility to stress-corrosion cracking high dislocation mobility reduces susceptibility. It was demonstrated during stress-corrosion tests on 7075-T73 specimens that had undergone prior plastic deformation, that the introduction of dislocations alone did not lower the dislocation mobility sufficiently to diminish the stress-corrosion resistance. This is in contrast to similar experiments with -T6 specimens, wherein precipitation was induced by similar deformation and the mobility was reduced sufficiently to lower the stress-corrosion resistance. An important role for immobilized dislocations was also suggested by a theoretical calculation of the stress field around an edge dislocation which neighbors a grain boundary precipitate. This calculation, which was based only on elasticity theory and thus precluded plastic flow, indicated that a large tensile stress, theoretically as high as 250,000 psi, could act normal to the precipitate-matrix interface. When the capacity for plastic flow i.e., the dislocation mobility was intentionally reduced by notching a stress-corrosion specimen, a rapid failure could be induced in normally resistant 7075-T73 alloy.

Descriptors:

• *ALUMINUM ALLOYS
• *STRESS CORROSION
• MICROSTRUCTURE
• DEFORMATION
• CRACKS
• GRAIN BOUNDARIES
• FRICTION
• TENSILE PROPERTIES
• FRACTOGRAPHY
• DISLOCATIONS

Subject Categories:

• Properties of Metals and Alloys

Distribution Statement:

APPROVED FOR PUBLIC RELEASE