Sea-Water Embrittlement of Titanium

Abstract

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.