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    Influence of Composition, Annealing Treatment, and Texture on the Fracture Toughness of Ti-5A1-2.5Sn Plate at Cryogenic Temperatures

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    The plane strain fracture toughness (KIc) and conventional tensile properties of two commercially produced 25.4-mm (1-in.) thick Ti-5A1-2.5Sn plates were determined at cryogenic temperatures. One plate was extra-low interstitial (ELI) grade, the other, normal interstitial. Portions of each plate were mill annealed at 1088 K (1500°F) followed by either air or furnace cooling. The tensile properties, flow curves, and KIc of these plates were determined at 295 K (room temperature), 77 K (liquid nitrogen temperature), and 20 K (liquid hydrogen temperature).

    The air-cooled ELI plate was the toughest material evaluated. The KIc of the furnace-cooled ELI plate was about 25 percent below that of the air-cooled ELI material. Cooling rate from the annealing temperature had no influence on the toughness of the normal interstitial plates, both of which had a KIc approximately half that of the air cooled ELI plate. The 20 K fracture toughness of the normal interstitial plates varied only slightly with specimen orientation. The LS toughness of both ELI plates was approximately 20 percent greater than the LT toughness.

    Based on these results and a study of the microstructural fracture mechanism, it is recommended that Ti-5A1-2.5Sn, which is to be used in applications requiring high fracture toughness, should have the lowest possible interstitial level and be air-cooled from the annealing treatment so as to prevent ordering.


    titanium, titanium alloys, cryogenics, plane strain fracture toughness (, K, Ic, ), microstructure, crystallographic texture, fracture properties

    Author Information:

    Van Stone, RH
    metallurgist, General Electric Corporate Research and Development Center, Schenectady, N. Y.

    Shannon, JL
    Head and engineer, NASA-Lewis Research Center, Cleveland, Ohio

    Pierce, WS
    Head and engineer, NASA-Lewis Research Center, Cleveland, Ohio

    Low, JR
    Professor, Carnegie-Mellon University, Pittsburgh, Pa.

    Committee/Subcommittee: E08.07

    DOI: 10.1520/STP26542S