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Fabrication of Fine Grain Size Shape Memory Alloys Through Crystallization of Amorphous Ribbon

Published online by Cambridge University Press:  15 February 2011

J. D. Shi ,
J. L. Ma ,
Y. Gao ,
Z. J. Pu  and
K. H. Wu
J. D. Shi
Affiliation:
Florida International University, Department of Mechanical Engineering, Miami, FL 33199
J. L. Ma
Affiliation:
Florida International University, Department of Mechanical Engineering, Miami, FL 33199
Y. Gao
Affiliation:
Florida International University, Department of Mechanical Engineering, Miami, FL 33199
Z. J. Pu
Affiliation:
Florida International University, Department of Mechanical Engineering, Miami, FL 33199
K. H. Wu
Affiliation:
Florida International University, Department of Mechanical Engineering, Miami, FL 33199
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Abstract

The objective of this work is to fabricate fine grain size NiTi-based shape memory alloys through crystallization of amorphous materials. An amorphous material with a composition of Ti50Ni25Cu25 was used as a sample for this study. First, a systematic investigation was conducted to understand the kinetics of the crystallization process of amorphous materials under an isothermal mode and under a continuous heating mode, respectively. The characteristic parameters associated with the crystallization process, such as the starting and finishing times for the isothermal crystallization process, the peak temperature for the continuous heating crystallization process, and the activation energy of the material were determined. Based on the results of the kinetic study, a series of isothermal annealing experiments were conducted to characterize the microstructure of the fully crystallized materials. The TEM micrographs indicate that the mean grain size of the fully crystallized Ti50Ni25Cu25 alloy is independ of isothermal temperature. The mean grain size is around 400-500nm, which is 1/10 of the grain size of usual NiTi based shape memory alloys. In addition, the crystallization micro-mechanism of the amorphous material is discussed based on TEM observations.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 400: Symposium E – Metastable Metal-Based Phases and Microstructures , 1995 , 221
Copyright
Copyright © Materials Research Society 1996

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