Accession Number : AD0733719

Title :   Fine Subgrain Structure Adjacent to Fatigue Cracks.

Descriptive Note : Technical rept. 1 Apr-15 Aug 71,

Corporate Author : MIDWEST RESEARCH INST KANSAS CITY MO

Personal Author(s) : Grosskreutz,J. C. ; Shaw,G. G.

Report Date : OCT 1971

Pagination or Media Count : 23

Abstract : Deformation microstructures adjacent to fatigue cracks in 2024-T4 and 7075-T6 aluminum, and Ti -6Al -4V alloys have been examined by transmission electron microscopy. The data show that material within 1-2 micrometer of a tensile-mode crack consists of very fine (0.1 micrometer) subgrains in all three materials. The average misorientation between the subgrains is 2-4 degrees. The presence of this substructure, which seems to be independent of initial metallurgical condition, is used to explain the weak dependence of Stage 2 crack growth rates on the initial condition in high stacking fault energy materials. No evidence of precipitate reversion was observed adjacent to the fatigue cracks in 7075-T6 aluminum. (Author)

Descriptors :   (*ALUMINUM ALLOYS, FRACTURE(MECHANICS)), (*TITANIUM ALLOYS, FRACTURE(MECHANICS)), CRYSTAL SUBSTRUCTURE, CRACKS, FATIGUE(MECHANICS), ELECTRON MICROSCOPY

Subject Categories : Metallurgy and Metallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE