Cracking of aluminium alloy valve body used in attitude control of satellite launch vehicle – A metallurgical investigation

Aluminium alloys emerged as preferred material for aerospace application, due to their high specific strength, high specific stiffness and ease for fabrication, Al–4.5Zn–1.5Mg aluminium alloy was used for the fabrication of a valve body for an attitude control system of satellite launch vehicles. During one of the functional qualification test, while charging the gaseous medium, a pressure drop was noticed. This was attributed to a leak through a crack opening of the valve body. Detailed metallurgical analysis indicated that the failure was due to stress corrosion cracking (SCC). aper brings out the metallurgical analysis carried out and remedial measures suggested.