Improvements in fracture properties of Ni-Ti superelastic alloy in physiological saline solution containing hydrogen peroxide by surface modification

Ken'ichi Yokoyama, Tokunori Kanemura, Jun'ichi Sakai

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    Abstract

    The fracture properties of surface-modified Ni-Ti superelastic alloy are examined by a sustained tensile-loading test in physiological saline solution containing hydrogen peroxide. The surface modification of the alloy is performed by chemical etching in 35 mass% nitric acid solution at 60 °C for a long time (3 h). By modifying the surface of the specimen, many corrosion pits are formed and the surface roughness increases. When the surface-modified specimen is immersed in the test solution without applied stress, corrosion occurs over the entire specimen and the amount of dissolved nickel ions increases. Nevertheless, under applied stress, the localized corrosion leading to the fracture is inhibited and the fracture mechanism changes, thereby increasing the time to fracture. The effects of the surface modification are confirmed even under applied stress above the critical stress for martensite transformation. The present study suggests that the effectiveness of the surface modification of Ni-Ti superelastic alloy should be investigated not only without applied stress but also under applied stress.

    Original languageEnglish
    Pages (from-to)267-275
    Number of pages9
    JournalMaterials Science and Engineering A
    Volume513-514
    Issue numberC
    DOIs
    Publication statusPublished - 2009 Jul 15

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    Keywords

    • Corrosion
    • Fracture
    • Hydrogen peroxide
    • Ni-Ti
    • Nitinol
    • Surface modification

    ASJC Scopus subject areas

    • Materials Science(all)
    • Condensed Matter Physics
    • Mechanical Engineering
    • Mechanics of Materials

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