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Proceedings Paper

Mechanical properties of Ti50Ni50-xCux(x=20, 25) shape memory alloy strips produced by melt overflow
Author(s): Yeon-wook Kim; Tae-hyun Nam
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Paper Abstract

Ti-Ni-Cu alloys have been known to be attractive shape memory alloys for applications as actuators because of large transformation elongation and small transformation hysteresis. However, Cu addition exceeding 10at% makes the alloys brittle and spoils the formability. Arc melt overflow enables Ti-Ni-Cu alloys with high Cu-content to be fabricated into thin strips. Then, the shape memory alloy strips of Ti50Ni30Cu20 and Ti50Ni25Cu25 have been fabricated by arc melt overflow technique. Their microstructures and shape memory characteristics were investigated by means of XRD, optical microscopy and DSC. The microstructure of as-cast strips exhibited columnar grains normal to the strip surface. X-ray diffraction analysis showed that the martensitic transformation of B2-B19 occurred in the alloy strips. During thermal cyclic deformation with the applied stress of 60 MPa, transformation hysteresis and elongation associated with the B2-B19 transformation were observed to be 4.9°C and 1.8% in Ti50Ni30Cu20 alloy strip and 3.5°C and 1.7% in Ti50Ni25Cu25 alloy strip. The as-cast strip of Ti50Ni25Cu25 alloy also showed a perfect superelasticity and its stress hysteresis was as small as 14 MPa. These mechanical properties and shape memory characteristics of the alloy strips were ascribed to B2-B19 transformation and the controlled microstructures produced by rapid solidification of the arc melt overflow process.

Paper Details

Date Published: 1 November 2007
PDF: 8 pages
Proc. SPIE 6423, International Conference on Smart Materials and Nanotechnology in Engineering, 64233C (1 November 2007); doi: 10.1117/12.780041
Show Author Affiliations
Yeon-wook Kim, Keimyung Univ. (South Korea)
Tae-hyun Nam, Gyeongsang National Univ. (South Korea)

Published in SPIE Proceedings Vol. 6423:
International Conference on Smart Materials and Nanotechnology in Engineering
Shanyi Du; Jinsong Leng; Anand K. Asundi, Editor(s)

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