Nanoindentation of binary and ternary Ni–Ti-based shape memory alloy thin films

A. J. Muir Wood, Sohrab Sanjabi, Yong Qing Fu, Zoe Barber, Bill Clyne

Research output: Contribution to journalArticlepeer-review

40 Citations (Scopus)

Abstract

Thin sputtered films of binary (Ni–Ti) and ternary (Ni–Ti–Hf and Ni–Ti–Cu) shape memory alloys have been subjected to nanoindentation over a range of temperature (up to 400 °C), using a small diameter spherical indenter. The load-displacement plots obtained during these experiments have been interpreted so as to reveal whether the imposed strain was being at least partly accommodated by the martensitic phase transformation, ie whether superelastic deformation was taking place. This was done by evaluating the remnant indent depth ratio (depth after unloading/depth at peak load), which is expected to have a relatively small value if superelastic deformation and recovery are significant. It is confirmed that this procedure, which has previously been validated for bulk material, can be applied to these thin films (~ 2 µm in thickness). The results indicate that ternary alloys with up to about 20 at.%Hf or 10 at.%Cu can exhibit superelastic behaviour over suitable temperature ranges.
Original languageEnglish
Pages (from-to)3115-3120
JournalSurface and Coatings Technology
Volume202
Issue number13
DOIs
Publication statusPublished - 25 Mar 2008

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