Effects of Phase Transformations on Fatigue Endurance of a Superelastic NiTi Alloy

    Volume 4, Issue 3 (March 2007)

    ISSN: 1546-962X

    CODEN: JAIOAD

    Published Online: 13 April 2007

    Page Count: 6


    Wu, Ming H.
    Memry Corporation, 3 Berkshire Boulevard, Bethel, CT

    (Received 23 May 2006; accepted 18 January 2007)

    Abstract

    It is well known that NiTi shape memory alloys exhibit superelasticity where a large elastic deformation proceeds under a constant stress due to the formation of stress-induced martensite. However, for most commercial NiTi alloys used in medical devices, the materials are processed in such a way that the R-phase transformation is apparently separated from the martensitic transformation. The B2 to R-phase change exhibits a much smaller shape change and a narrower hysteresis than does the B2 to B19 martensite transformation. Hence, the transformation temperatures as well as the thermomechanical properties associated with the R-phase are much more stable during cyclic deformation when compared to those associated with the B19martensite. The crystallographic features for both martensitic and R-phase transformations are reviewed, and their effects on the tensile properties and rotating-beam fatigue endurance are studied in the present paper.


    Paper ID: JAI100657

    DOI: 10.1520/JAI100657

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    Author
    Title Effects of Phase Transformations on Fatigue Endurance of a Superelastic NiTi Alloy
    Symposium Fatigue and Fracture of Medical Metallic Materials and Devices, 2005-11-11
    Committee E08