Accession Number : AD0732321

Title :   Influence of Microstructure on the Mechanical Properties and Stress Corrosion Susceptibility of 7075 Aluminum Alloy.

Descriptive Note : Research memo.,

Corporate Author : GRUMMAN AEROSPACE CORP BETHPAGE N Y RESEARCH DEPT

Personal Author(s) : Adler,Philip ; DeIasi,Richard ; Geschwind,Gary

Report Date : NOV 1971

Pagination or Media Count : 52

Abstract : Matrix and grain boundary features were systematically varied, using appropriate heat treatment, to evaluate their significance in changing the mechanical and stress corrosion properties of 7075 aluminum alloy. Maximum strength is associated with a Guinier-Preston zone matrix. The precipitate-free-zone adjacent to high angle grain boundaries was found to have only a slight effect on yield and tensile strength and a greater influence on hardness. Stress corrosion susceptibility was studied in a chloride ion environment over a 0.7 - 3.5 pH range. Differences in pH-dependent susceptibility associated exclusively with grain boundary structure for material of highest strength were observed. Grain boundary precipitate spacing (inversely related to precipitate density) was found to be of primary importance to susceptibility. The relative importance of crack initiation to the over-all stress corrosion process was also found to be dependent on grain boundary microstructure. These results indicate that improved properties for Al-Mg-Zn type alloys can be attained by a desirable combination of matrix and grain boundary structure. (Author)

Descriptors :   (*ALUMINUM ALLOYS, MICROSTRUCTURE), (*STRESS CORROSION, ALUMINUM ALLOYS), MECHANICAL PROPERTIES, GRAIN BOUNDARIES, HEAT TREATMENT, ELECTRON MICROSCOPY

Subject Categories : Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE