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Crystallization of Amorphous Sputtered NiTi Shape-Memory Alloy Films

Published online by Cambridge University Press:  21 February 2011

F.F. Gong ,
H.M. Shen  and
Y.N. Wang
F.F. Gong
Affiliation:
National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210008, P.R. China
H.M. Shen
Affiliation:
National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210008, P.R. China
Y.N. Wang
Affiliation:
National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210008, P.R. China
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Abstract

The crystallization of amorphous sputtered NiTi films was investigated for selected heat treatments. From x-ray diffraction patterns, when the films were annealed below the crystallization temperature, the intensity of the broad maximum centered at 2θ = 43.5° increased with increasing the annealing temperature and time. When the films were annealed at 550°C for 0.5hr, parent B2 phase and Ni4Ti3 precipitates appeared. For annealing temperature above 700°C, the films showed embrittlement and volatilization. Therefore the optimum heat treatment for the optimum shape memory effect is found. The average grain size increased slowly in the initial stage of annealing but remained almost unchanged when the films were annealed for more than 1hr. This is because the grain boundary grooving caused by the titanium at a certain temperature volatilization seriously hinder the grain growth.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 398: Symposium C – Thermodynamics and Kinetics of Phase Transformations , 1995 , 405
Copyright
Copyright © Materials Research Society 1998

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References

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