No 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.

A technique of melting, processing, and testing small (80 g) rods of titanium alloys has been developed. The technique is designed for screening large numbers of alloy formulations to determine those with enough potential for further evaluation. The hearth plate of an arc button-melting furnace was modified to produce rod ingots which are forged to a shape suitable for testing. Strength and toughness measurements are used to compare a series of alloys relatively, and with respect to their bulk properties. It is recognized that a number of factors, such as cooling rates and amount of forging, prevent duplication of production material properties. Nevertheless, the apparent alloying and microstructural effects and the degree of correlation with plate properties are discussed.

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