Precipitation and thermal fatigue in Ni-Ti-Zr shape memory alloy thin films by combinatorial nanocalorimetry

Patrick J. McCluskey, Chunwang Zhao, Ofer Kfir, Joost J. Vlassak

Research output: Contribution to journalArticlepeer-review

34 Scopus citations

Abstract

Thin-film samples of Ni-Ti-Zr shape memory alloys were studied by combinatorial nanocalorimetry to determine the effects of high-temperature (900 °C) heat treatments and low-temperature (450 °C) thermal cycling on the characteristics of the martensite transformation. The response of the samples to heat treatments depends on composition and is controlled by a precipitation mechanism. Two precipitate types, a Ti2Ni-base phase at low Zr concentration and a Ni10Zr7-base phase at high Zr concentration, affect the martensite transformation characteristics by altering the composition and the stress state of the shape memory phase. Thermal fatigue behavior, induced by thermal cycling, is improved compared to previous results. The most stable sample demonstrates a transformation temperature reduction of just 11 °C for 100 cycles. The improved stability of the samples is attributed to the very small grain size of approximately 5-20 nm. The high heating and cooling rates characteristic of nanocalorimeters allowed this study to be performed in a high-throughput manner with efficiencies not previously achieved.

Original languageEnglish
Pages (from-to)5116-5124
Number of pages9
JournalActa Materialia
Volume59
Issue number13
DOIs
StatePublished - Aug 2011

Funding

FundersFunder number
National Science FoundationECS-0335765
Air Force Office of Scientific ResearchFA9550-08-1-0374
Materials Research Science and Engineering Center, Harvard University

    Keywords

    • Nanocalorimetry
    • Nanocrystalline material
    • Plastic deformation
    • Precipitation
    • Shape memory alloys

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