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In situ Transmission Electron Microscopy and Nanoindentation Studies of Phase Transformation and Pseudoelasticity of Shape-memory Titanium-nickel Films

Published online by Cambridge University Press:  01 July 2005

X.-G. Ma  and
K. Komvopoulos
X.-G. Ma
Affiliation:
Department of Mechanical Engineering, University of California, Berkeley, California 94720
K. Komvopoulos*
Affiliation:
Department of Mechanical Engineering, University of California, Berkeley, California 94720
*
a)Address all correspondence to this author. e-mail: kyriakos@me.berkeley.edu
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Abstract

Transmission electron microscopy (TEM) and nanoindentation, both with in situ heating capability, and electrical resistivity measurements were used to investigate phase transformation phenomena and thermomechanical behavior of shape-memory titanium-nickel (TiNi) films. The mechanisms responsible for phase transformation in the nearly equiatomic TiNi films were revealed by heating and cooling the samples inside the TEM vacuum chamber. Insight into the deformation behavior of the TiNi films was obtained from the nanoindentation response at different temperatures. A transition from elastic-plastic to pseudoelastic deformation of the martensitic TiNi films was encountered during indentation and heating. In contrast to the traditional belief, the martensitic TiNi films exhibited a pseudoelastic behavior during nanoindentation within a specific temperature range. This unexpected behavior is interpreted in terms of the evolution of martensitic variants and changes in the mobility of the twinned structures in the martensitic TiNi films, observed with the TEM during in situ heating.

Keywords

Crystallographic structureNanoindentationTransmission electron microscopy (TEM)
Type
Articles
Information
Journal of Materials Research , Volume 20 , Issue 7 , July 2005 , pp. 1808 - 1813
Copyright
Copyright © Materials Research Society 2005

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References

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