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Effects of Cu on the microstructural and mechanical properties of sputter deposited Ni-Ti thin films

Effects of Cu on the microstructural and mechanical properties of sputter deposited Ni-Ti thin films
Effects of Cu on the microstructural and mechanical properties of sputter deposited Ni-Ti thin films
The microstructure of sputter deposited Ti-rich Ni-Ti thin films doped with Cu in the range 0–20.4 at.% and annealed for 1 h at 500 and 600 °C has been investigated and correlated with the mechanical properties of the films measured by depth-sensing nanoindentation. X-ray diffraction analysis showed the microstructural evolution of Ni-Ti thin films when doped with Cu and annealed at different temperatures. Heat treatments promoted the nucleation and growth of Ti2Ni precipitates in Ti-rich Ni-Ti thin films, which affected the stability of austenitic and martensitic phases at ambient temperature. Doping with Cu caused the formation of Ti(Ni, Cu)2 plate precipitates, which became more finely and densely dispersed in the grains with increasing Cu content. TEM analysis showed a columnar grain morphology extended through the whole films thickness, while with increasing Cu content a noticeable lateral grain refinement was induced by segregation of a (Ni, Cu)-rich phase to grain boundaries. The nano-hardness increased almost linearly with increasing Cu content owing to this grain refinement, though differences between samples annealed at different temperatures were found which could be related to the evolution of Ti(Ni, Cu)2 plate precipitates with annealing temperature and Cu content. The Young's modulus exhibited a similar dependence on Cu content as nano-hardness, though no significant differences were observed with increasing annealing temperatures.
shape memory alloys, thin films, magnetron, sputtering, nanoindentation, grain boundary segregation, precipitation
0257-8972
261-268
Callisti, M.
86e03724-aacc-46d5-bccc-4c7025556667
Tichelaar, F.D.
83605204-7d2d-4497-88cf-8743909e7a05
Mellor, B.G.
2b13b80f-880b-49ac-82fe-827a15dde2fe
Polcar, T.
c669b663-3ba9-4e7b-9f97-8ef5655ac6d2
Callisti, M.
86e03724-aacc-46d5-bccc-4c7025556667
Tichelaar, F.D.
83605204-7d2d-4497-88cf-8743909e7a05
Mellor, B.G.
2b13b80f-880b-49ac-82fe-827a15dde2fe
Polcar, T.
c669b663-3ba9-4e7b-9f97-8ef5655ac6d2

Callisti, M., Tichelaar, F.D., Mellor, B.G. and Polcar, T. (2013) Effects of Cu on the microstructural and mechanical properties of sputter deposited Ni-Ti thin films. [in special issue: Proceedings of the 40th International Conference on Metallurgical Coatings and Thin Films (ICMCTF 2013)] Surface and Coatings Technology, 237, 261-268. (doi:10.1016/j.surfcoat.2013.06.040).

Record type: Article

Abstract

The microstructure of sputter deposited Ti-rich Ni-Ti thin films doped with Cu in the range 0–20.4 at.% and annealed for 1 h at 500 and 600 °C has been investigated and correlated with the mechanical properties of the films measured by depth-sensing nanoindentation. X-ray diffraction analysis showed the microstructural evolution of Ni-Ti thin films when doped with Cu and annealed at different temperatures. Heat treatments promoted the nucleation and growth of Ti2Ni precipitates in Ti-rich Ni-Ti thin films, which affected the stability of austenitic and martensitic phases at ambient temperature. Doping with Cu caused the formation of Ti(Ni, Cu)2 plate precipitates, which became more finely and densely dispersed in the grains with increasing Cu content. TEM analysis showed a columnar grain morphology extended through the whole films thickness, while with increasing Cu content a noticeable lateral grain refinement was induced by segregation of a (Ni, Cu)-rich phase to grain boundaries. The nano-hardness increased almost linearly with increasing Cu content owing to this grain refinement, though differences between samples annealed at different temperatures were found which could be related to the evolution of Ti(Ni, Cu)2 plate precipitates with annealing temperature and Cu content. The Young's modulus exhibited a similar dependence on Cu content as nano-hardness, though no significant differences were observed with increasing annealing temperatures.

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e-pub ahead of print date: 18 June 2013
Published date: 25 December 2013
Keywords: shape memory alloys, thin films, magnetron, sputtering, nanoindentation, grain boundary segregation, precipitation
Organisations: Engineering Mats & Surface Engineerg Gp

Identifiers

Local EPrints ID: 361292
URI: https://eprints.soton.ac.uk/id/eprint/361292
ISSN: 0257-8972
PURE UUID: 56e4a1ca-a621-4349-9ff8-4b367f7c82b9
ORCID for T. Polcar: ORCID iD orcid.org/0000-0002-0863-6287

Catalogue record

Date deposited: 17 Jan 2014 16:50
Last modified: 19 Oct 2018 00:31

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