Phase transformation evolution in NiTi shape memory alloy under cyclic nanoindentation loadings at dissimilar rates

Abbas Amini, Chun Cheng, Qianhua Kan, Minoo Naebe, Haisheng Song

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    18 Citations (Scopus)

    Abstract

    Hysteresis energy decreased significantly as nanocrystalline NiTi shape memory alloy was under triangular cyclic nanoindentation loadings at high rate. Jagged curves evidenced discrete stress relaxations. With a large recovery state of maximum deformation in each cycle, this behavior concluded in several nucleation sites of phase transformation in stressed bulk. Additionally, the higher initial propagation velocity of interface and thermal activation volume, and higher levels of phase transition stress in subsequent cycles explained the monotonic decreasing trend of dissipated energy. In contrast, the dissipated energy showed an opposite increasing trend during triangular cyclic loadings at a low rate and 60sec holding time after each unloading stage. Due to the isothermal loading rate and the holding time, a major part of the released latent heat was transferred during the cyclic loading resulting in an unchanged phase transition stress. This fact with the reorientation phenomenon explained the monotonic increasing trend of hysteresis energy.
    Original languageEnglish
    Article number3412
    Number of pages7
    JournalScientific Reports
    Volume3
    DOIs
    Publication statusPublished - 2013

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