STP432: Effects of Heat Treating Environmental Conditions on the Stress-Corrosion Cracking Resistance of Several Titanium Alloys

    Howe, DG
    Research physical metallurgistspersonal member, U.S. Naval Research LaboratoryASTM, Washington, D.C.,

    Goode, RJ
    Research physical metallurgistspersonal member, U.S. Naval Research LaboratoryASTM, Washington, D.C.,

    Pages: 13    Published: Jan 1968


    Abstract

    The effects of heat treating environmental conditions on the stress-corrosion-cracking resistance of several titanium alloys have been studied. The alloys studied in this investigation were the Ti-8Al-1Mo-1V, Ti-7Al-1Mo-1V, Ti-6Al-4V, and Ti-7Al-2.5Mo alloys. Precracked cantilever type specimens were heat treated in either an inert atmosphere or in vacuum and tested in a 3.5 per cent salt water solution. A comparison of the stress intensity required for failure in salt water with that required for “dry” mechanical fracture indicates that all of these alloys become essentially insensitive to the aqueous environment when vacuum solution annealed and helium gas cooled. Similar heat treatments in argon or helium developed a wide range in level of stress-corrosion-cracking resistance for these alloys; the level was dependent upon the temperatures used. The environmental conditions associated with aging treatments at 1200F following the solution anneal appear to have little effect on the stress-corrosion-cracking resistance of these alloys. Comparison of the stress-corrosion-cracking data with hydrogen content before and after treatment indicates a close connection between stress-corrosion-cracking sensitivity and hydrogen content in the material even at very low hydrogen levels. These results suggest that hydrogen contained in the metal may play an important role in the stress-corrosion cracking process of titanium alloys.

    Keywords:

    titanium alloys, stress corrosion cracking, heat treatment, vacuum annealing, mechanical properties, fracture toughness, process variables


    Paper ID: STP33625S

    Committee/Subcommittee: B10.01

    DOI: 10.1520/STP33625S


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