Mechanisms of Stress Corrosion Cracking of Titanium-Aluminum Alloys in Methanol-HCl Solutions

Initiation and early slow growth of stress corrosion cracks in Ti-Al alloys in methanol-HCl solutions occurs by slip-induced grain boundary splitting. Later crack propagation occurs by cleavage and other forms of transgranular cracking. Crack initiation and failure by stress corrosion cracking (SCO can occur at stresses far below the microyield stress because of localized slip in isolated groups of grains. Increases in aluminum content and precipitation of Ti3Al enhance SCC susceptibility because of intensification of slip bands and inhibition of plastic relaxation.