Delayed fracture of Ni-Ti superelastic alloys in acidic and neutral fluoride solutions

Ken'ichi Yokoyama*, Kazuyuki Kaneko, Keiji Moriyama, Kenzo Asaoka, Jun'ichi Sakai, Michihiko Nagumo

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    61 Citations (Scopus)


    Hydrogen-related degradation of the mechanical properties of a Ni-Ti superelastic alloy has been examined by means of delayed fracture tests in acidic and neutral fluoride solutions and hydrogen thermal desorption analysis. Delayed fracture took place in both solutions; the time to fracture was shorter in the acidic solutions than in the neutral solutions with the same fluoride concentration. The time to fracture was reduced in both solutions when applied stress exceeded the critical stress for martensite transformation. In the acidic solutions, Ni-Ti superelastic alloy underwent general corrosion and absorbed substantial amounts of hydrogen. Fractographic features suggested that the delayed fracture in the acidic solutions was attributable to hydrogen embrittlement, whereas in the neutral solutions, a different fracture mode appeared associated with localized corrosion only in the vicinity of the fracture initiation area. In the neutral solutions, the amount of absorbed hydrogen was much less than that in the acidic solutions, and the delayed fracture was likely to be induced by active path corrosion accompanying hydrogen absorption. The results of the present study imply that the hydrogen-related degradation of performance of Ni-Ti superelastic alloys occurs in the presence of fluoride.

    Original languageEnglish
    Pages (from-to)105-113
    Number of pages9
    JournalJournal of Biomedical Materials Research - Part A
    Issue number1
    Publication statusPublished - 2004 Apr 1


    • Corrosion
    • Delayed fracture
    • Fluoride
    • Hydrogen embrittlement
    • Ni-Ti

    ASJC Scopus subject areas

    • Biomedical Engineering
    • Biomaterials


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