Formation of Ti₃Al and its embrittling effects on titanium-aluminum alloys

The formation of Ti₃Al and its embrittling characteristics have been investigated in Ti-Al binary alloys up to 9.0 weight percent aluminum. The investigating tools were optical metallography, the Brown-type stress corrosion test and the Charpy V-notch Impact test. Segregated microstructures resulting from annealing in the (α+β) region were found to be extremely difficult to homogenize below the α-transus and could possibly explain the two-phase regions reported by many investigators. Sea-water stress corrosion tests reveal that a Widmanstatten structure is susceptible to stress corrosion cracking after aging for two hours at 1100°F. Much longer annealing times are required to produce susceptibility in equiaxed α-grains resulting from annealing in the (α+β) region. Toughness is less affected as a result of aging a Widmanstatten structure than an equiaxed structure, although the reduction is significant in both cases.