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Atomistic Simulation of Radiation-Induced Amorphization of the B2 Ordered Intermetallic Compound NiTi

Published online by Cambridge University Press:  26 February 2011

Michael J. Sabochick  and
Nghi Q. Lam
Michael J. Sabochick
Affiliation:
Air Force Institute of Technology, Department of Engineering Physics, Wright-Patterson Air Force Base, OH 45-133-65S3
Nghi Q. Lam
Affiliation:
Argonne National Laboratory, Materials Science Division, Argonne, IL 60-139
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Abstract

Amorphization of the B2 intermetallic compound NiTi under electron irradiation has been investigated using molecular dynamics. The effect of irradiation was simulated using two processes: 1) Ni and Ti atoms were exchanged, resulting in chemical disorder, and 2) Frenkel pairs were introduced, leading to the formation of stable point defects and also chemical disorder upon mutual recombination of interstitials and vacancies. After ∼0.1 exchanges per atom, the first process resulted in an energy increase of approximately 0.11 eV/atom and a volume increase of 1.91%. On the other hand, after introducing ∼0.5 Frenkel pairs per atom, the second process led to smaller increases of 0.092 eV/atom in energy and 1.43% in volume. The calculated radial distribution functions (RDFs) were essentially identical to each other and to the calculated RDF of a quenched liquid. The structure factor, however, showed that long-range order was still present after atom exchanges, while the introduction of Frenkel pairs resulted in the loss of long-range order. It was concluded that point defects are necessary for amorphization to occur in NiTi, although chemical disorder alone is capable of storing enough energy to make the transition possible.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 201: Symposium A – Surface Chemistry and Beam-Solid Interactions , 1990 , 387
Copyright
Copyright © Materials Research Society 1991

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