Studies on retrogression and reageing of aluminium zinc magnesium 7075 alloy

Abstract

Aluminium alloys of 7000series (7075) are known for their excellent combination of characteristics such as low density, castability, machinability and good mechanical properties. Their good surface finish, light weight, resistance to wear and corrosion, high strength to weight ratio and good cryogenic properties make them versatile, particularly in automobiles, aerospace and marine sectors. The other important properties, viz., low melting temperature, ease of handling, easy formability and recycling have led to increased demand for AA7075 Al alloy (American Association 7075) components. newlineLiterature survey has been carried out from the available resources covering published literature on materials, methods, processing of alloys, evaluation of mechanical properties, fatigue strength, and wear characteristics. Based on literature survey, AA7075 aluminium alloys was selected for the study. Specifically, the study had the following scope: newlineCasting of alloy and evaluation of its composition. newlineHeat treatment of alloy. newlineRetrogression and re-aging of the above alloys. newlineMicrostructure analysis with optical microscope (OM). newlineEvaluation of mechanical properties. newlineEvaluation of fatigue strength. newlineWear studies using optical and scanning electron microscopes. newlineAnalysis of results and drawing conclusions. newlinePublication of results obtained from time to time. newlineix newlineIn this study AA7075 Al alloy in addition to heat treated to solution temperature, specimens subjected to varied ageing times and ageing temperatures (procedure is known as retrogression and re-ageing ie.RRA) were observed for their microstructure, hardness, tensile strength, fatigue, and wear characteristics study as per relevant standard procedures. newlineAA7075 Al alloy is classified under 7xxx series of alloys and major alloying element is zinc. Its composition includes 5.1-6.1% zinc, 2.1-2.9% magnesium, 1.2-2.0% copper, and less than 0.5% of silicon, iron, manganese, titanium, chromium, and other metals. It is generally produced in several heat temper grades such as 7075-O, 7075-T6,