Mechanical properties of Ti50Ni50-xCux(x=20, 25) shape memory alloy strips produced by melt overflow

Yeon-wook Kim; Tae-hyun Nam

doi:10.1117/12.780041

1 November 2007 Mechanical properties of Ti₅₀Ni_50-xCu_x(x=20, 25) shape memory alloy strips produced by melt overflow

Yeon-wook Kim, Tae-hyun Nam

Proceedings Volume 6423, International Conference on Smart Materials and Nanotechnology in Engineering; 64233C (2007) https://doi.org/10.1117/12.780041
Event: International Conference on Smart Materials and Nanotechnology in Engineering, 2007, Harbin, China

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.

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Yeon-wook Kim and Tae-hyun Nam "Mechanical properties of Ti₅₀Ni_50-xCu_x(x=20, 25) shape memory alloy strips produced by melt overflow", Proc. SPIE 6423, International Conference on Smart Materials and Nanotechnology in Engineering, 64233C (1 November 2007); https://doi.org/10.1117/12.780041

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KEYWORDS

Copper

Nickel

Solids

Titanium

Shape memory alloys

Actuators

Temperature metrology

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