Accession Number : AD0820137

Title :   DEVELOPMENT OF HIGH-STRENGTH ALUMINUM ALLOYS WITH IMPROVED STRESS-CORROSION RESISTANCE.

Descriptive Note : Summary technical rept. 1 May 66-30 Apr 67,

Corporate Author : BOEING COMMERCIAL AIRPLANE CO RENTON WA

Personal Author(s) : McMillan, J. Corey ; Hyatt, Michael V.

Report Date : JUN 1967

Pagination or Media Count : 97

Abstract : The objective of the program is to develop a stress corrosion resistant high strength aluminum alloy through addition of minor elements and variations in heat treatment. In Phase I, fifteen special chemistry alloys based on the 7075 composition were prepared in plate form with additions of silver, boron, cerium, yttrium and zirconium. The materials evaluation consisted of metallographic and aging studies, stress corrosion testing and determination of mechanical and fracture properties. The silver bearing alloys, while not immune, were the only alloys to show increased resistance to stress corrosion cracking in the T6 temper. Overaging treatments improved the stress corrosion resistance of all alloy combinations tested. Mechanical property evaluations and transmission electron microscopy studies indicate that silver additions retard the rate of overaging and promote a finer dispersion of M' precipitate, which allow these materials to attain stress corrosion resistance without large decreases in tensile strength. However, the increased quench sensitivity of silver-bearing alloys may limit this strength advantage to thinner sections unless other changes are made in chemical composition. On the basis of stress corrosion, fatigue, fracture toughness, and strength requirements, five step-aged special chemistry alloys are proposed for Phase II testing. (Author)

Descriptors :   (*ALUMINUM ALLOYS, CORROSION RESISTANCE), STRESS CORROSION, HEAT TREATMENT, ADDITIVES, METALLOGRAPHY, AGING(MATERIALS), MECHANICAL PROPERTIES, FRACTURE(MECHANICS), FATIGUE(MECHANICS), TENSILE PROPERTIES, QUENCHING, DISPERSION RELATIONS, MICROSTRUCTURE, SILVER, BORON, CERIUM, YTTRIUM, ZIRCONIUM.

Subject Categories : Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE