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Direct Measurement of the Nanoscale Mechanical Properties of NiTi Shape Memory Alloy

Published online by Cambridge University Press:  01 February 2011

Gordon A. Shaw  and
Wendy C. Crone
Gordon A. Shaw
Affiliation:
Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, U.S.A.
Wendy C. Crone
Affiliation:
Department of Engineering Physics, University of Wisconsin-Madison, Madison, WI 53706, U.S.A.
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Abstract

The mechanical properties of sputter-deposited NiTi shape memory alloy thin films ranging in thickness from 35 nm to 10 μm were examined using nanoindentation and atomic force microscopy (AFM). Indents made in films as thin as 150 nm showed partial shape recovery upon heating, although film thickness was found to have a marked effect on the results. A modified spherical cavity model is used to describe the findings, which suggest that the substrate tends block the shape memory effect as film thickness decreases below a threshold level which is specific to applied load. This has the net effect of decreasing the indent recovery below the critical film thickness. The fact that the spherical cavity model predicts the critical film thickness at which the shape memory effect is blocked indicates that the increased recovery of nanoscale indentations is due to a suppression of plastic processes rather than an enhancement of shape memory processes.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 791: Symposium Q – Mechanical Properties of Nanostructured Materials and Nanocomposites , 2003 , Q7.11
Copyright
Copyright © Materials Research Society 2004

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References

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