Study of Martensitic Phase Transformation in a NiTiCu Thin‐Film Shape‐Memory Alloy Using Photoelectron Emission Microscopy |
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| Authors: | M. Cai S. C. Langford M. Wu W. Huang G. Xiong T. C. Droubay A. G. Joly K. M. Beck W. P. Hess J. T. Dickinson |
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| Affiliation: | 1. Department of Physics and Astronomy, Washington State University, Pullman, WA 99164, USA;2. School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore;3. Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA |
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| Abstract: | Thermally induced martensitic phase transformation in a polycrystalline NiTiCu thin‐film shape‐memory alloy is probed using 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, because of the lower work function of the martensite. UV 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 disappears suddenly during heating and reappears suddenly during subsequent cooling. These trenches are also characterized using atomic force microscopy at selected temperatures. The implications of these observations with respect to the spatial distribution of phases during thermal cycling in this thin‐film shape‐memory alloy are discussed. |
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| Keywords: | Phase‐change materials Polycrystalline materials Shape‐memory materials Thin films |
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