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Title: Study of Martensitic Phase transformation in a NiTiCu Thin Film Shape Memory Alloy Using Photoelectron Emission Microscopy

Abstract

The thermally-induced martensitic phase transformation in a polycrystalline NiTiCu thin film shape memory alloy was probed by photoelectron emission microscopy (PEEM). In situ PEEM images reveal distinct changes in microstructure and photoemission intensity at the phase transition temperatures. In particular, images of the low temperature, martensite phase are brighter than that of the high temperature, austenite phase, due to the relatively lower work function of the martensite. Ultra-violet photoelectron spectroscopy shows that the effective work function changes by about 0.16 eV during thermal cycling. In situ PEEM images also show that the network of trenches observed on the room temperature film disappear suddenly during heating and reappear suddenly during subsequent cooling. These trenches are also characterized by atomic force microscopy at selected temperatures. We describe implications of these observations with respect to the spatial distribution of phases during thermal cycling in this thin film shape memory alloy.

Authors:
; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
898086
Report Number(s):
PNNL-SA-49610
10196; 6292a; 6292; KC0301020; TRN: US200705%%403
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Advanced Functional Materials, 17(1):161-167
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; NICKEL ALLOYS; TITANIUM ALLOYS; COPPER ALLOYS; MARTENSITE; MICROSTRUCTURE; PHASE TRANSFORMATIONS; THERMAL CYCLING; THIN FILMS; TRANSITION TEMPERATURE; WORK FUNCTIONS; Environmental Molecular Sciences Laboratory

Citation Formats

Cai, Mingdong, Langford, Stephen C., Wu, Maggie J., Huang, W. M., Xiong, Gang, Droubay, Timothy C., Joly, Alan G., Beck, Kenneth, Hess, Wayne P., and Dickinson, J. T. Study of Martensitic Phase transformation in a NiTiCu Thin Film Shape Memory Alloy Using Photoelectron Emission Microscopy. United States: N. p., 2007. Web. doi:10.1002/adfm.200600611.
Cai, Mingdong, Langford, Stephen C., Wu, Maggie J., Huang, W. M., Xiong, Gang, Droubay, Timothy C., Joly, Alan G., Beck, Kenneth, Hess, Wayne P., & Dickinson, J. T. Study of Martensitic Phase transformation in a NiTiCu Thin Film Shape Memory Alloy Using Photoelectron Emission Microscopy. United States. doi:10.1002/adfm.200600611.
Cai, Mingdong, Langford, Stephen C., Wu, Maggie J., Huang, W. M., Xiong, Gang, Droubay, Timothy C., Joly, Alan G., Beck, Kenneth, Hess, Wayne P., and Dickinson, J. T. Mon . "Study of Martensitic Phase transformation in a NiTiCu Thin Film Shape Memory Alloy Using Photoelectron Emission Microscopy". United States. doi:10.1002/adfm.200600611.
@article{osti_898086,
title = {Study of Martensitic Phase transformation in a NiTiCu Thin Film Shape Memory Alloy Using Photoelectron Emission Microscopy},
author = {Cai, Mingdong and Langford, Stephen C. and Wu, Maggie J. and Huang, W. M. and Xiong, Gang and Droubay, Timothy C. and Joly, Alan G. and Beck, Kenneth and Hess, Wayne P. and Dickinson, J. T.},
abstractNote = {The thermally-induced martensitic phase transformation in a polycrystalline NiTiCu thin film shape memory alloy was probed by photoelectron emission microscopy (PEEM). In situ PEEM images reveal distinct changes in microstructure and photoemission intensity at the phase transition temperatures. In particular, images of the low temperature, martensite phase are brighter than that of the high temperature, austenite phase, due to the relatively lower work function of the martensite. Ultra-violet photoelectron spectroscopy shows that the effective work function changes by about 0.16 eV during thermal cycling. In situ PEEM images also show that the network of trenches observed on the room temperature film disappear suddenly during heating and reappear suddenly during subsequent cooling. These trenches are also characterized by atomic force microscopy at selected temperatures. We describe implications of these observations with respect to the spatial distribution of phases during thermal cycling in this thin film shape memory alloy.},
doi = {10.1002/adfm.200600611},
journal = {Advanced Functional Materials, 17(1):161-167},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Photoemission electron microscopy, in conjunction with photoemission spectroscopy, reflectivity, and surface roughness measurements, is used to study the thermally-induced martensitic transformation in a CuZnAI shape memory alloy. Real-time phase transformation is observed as a nearly instantaneous change of photoelectron intensity, accompanied by microstructural deformation and displacement due to the shape memory effect. The difference in the photoelectron intensity before and after the phase transformation is attributed to the concomitant change of work function as measured by photoelectron spectroscopy. Photoemission electron microscopy is shown to be a valuable new technique facilitating the study of phase transformations in shape memory alloys, andmore » provides real-time information on microstructural changes and phase-dependent electronic properties.« less
  • Thermally-induced martensitic phase transformations in polycrystalline CuZnAl and thin-film NiTiCu shape memory alloys were probed using photoemission electron microscopy (PEEM). Ultra-violet photoelectron spectroscopy shows a reversible change in the apparent work function during transformation, presumably due to the contrasting surface electronic structures of the martensite and austenite phases. In situ PEEM images provide information on the spatial distribution of these phases and the evolution of the surface microstructure during transformation. PEEM offers considerable potential for improving our understanding of martensitic transformations in shape memory alloys in real time.
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