Results of concentrated investigations on the sea-water stress corrosion of titanium indicate that the behavior is dependent on certain mechanical factors and on the metallurgical structure. The mechanical factors include a requirement that localized plastic deformation induce the formation of a coarse slip step. A possible further requirement is that the slip step occurs under crevice conditions. Recent work on the titanium-aluminum system, including kinetics of reactions occurring in the system, add to the evidence that stress corrosion is associated with the presence of the coherent Ti3Al precipitate. The most effective method for control of stress corrosion in titanium alloys containing aluminum is inhibition of the formation of Ti3Al by control of composition and heat treatment.

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Tests on titanium alloy cantilever beam specimens indicate that sea-water embrittlement behavior is related to aluminum content, aging in the range 900 to 1300 F, presence of isomorphous beta stabilizers (molybdenum, vanadium, columbium), and rate of cooling from annealing temperatures. The authors believe that during thermal cycling, regions of coherent Ti3Al are nucleated in equilibrium with an alpha matrix. Composition and time at temperature influence this embrittling process. To reduce embrittlement, (1) lower aluminum content, (2) add elements (molybdenum or vanadium) that suppress the formation of coherent Ti3Al, and (3) avoid or minimize thermal cycling in the critical range. Test results indicate that sea water embrittlement is an environmental-dependent brittleness triggered by an aqueous corrodent.