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The Transformation Characteristics in Thin Film SMA Heterostructures— The Importance of Interfacial Stress Accommodation

Published online by Cambridge University Press:  15 February 2011

Susan Z. Hua ,
C. M. Su  and
M. Wuttig
Susan Z. Hua
Affiliation:
Department of Materials and Nuclear Engineering, University of Maryland, College Park, MD 20742-2115
C. M. Su
Affiliation:
Department of Materials and Nuclear Engineering, University of Maryland, College Park, MD 20742-2115
M. Wuttig
Affiliation:
Department of Materials and Nuclear Engineering, University of Maryland, College Park, MD 20742-2115
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Abstract

Shape memory alloy (SMA) thin films have attracted attention due to their potential application as actuators in micromechanical systems. The stress development in Ni50Ti50 films has been measured using a cantilever beam method. It is of interest to study their transformation characteristics. We have investigated a striking change of the stress during the B2-B19 transformation. The magnitude of this stress depends on the film thickness and reflects the interface constraint. In order to obtain direct information about the interface, in situ cross-section TEM observations of NiTi/SiO2/Si heterostructures were performed at various temperatures. A layer of parent phase at the film/substrate interface was found to buffer the transformation induced stress. The origin and effect of this buffer layer was analysed based on the TEM cross-sectional observations of the formation history of the layer.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 308: Symposium M1 – Thin Films: Stresses and Mechanical Properties IV , 1993 , 33
Copyright
Copyright © Materials Research Society 1993

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References

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