Metallurgical investigation of cracked aluminium alloy valve

1-s2-0-s2213290213000096-gr1A case study published in « Case Studies in Engineering Failure Analysis« , July 2013.

The high strength aluminium alloy Al–5.5Zn–2.5Mg–1.5Cu (AA7075) is being widely used in realisation of aerospace components. A component ‘fill and vent valve’ used in liquid propulsion system was fabricated from AA 7075 forgings in T7352 temper condition, and subsequently undergone various functional tests, four years back. Recently, during dye penetrant test after proof pressure test at 525 bar, a valve indicated presence of a crack. Detailed metallurgical investigation indicated that failure was caused by stress corrosion cracking.

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