Table of Contents
Smart Materials Research
Volume 2016, Article ID 7512642, 12 pages
http://dx.doi.org/10.1155/2016/7512642
Research Article

Atomistic Study on Size Effects in Thermally Induced Martensitic Phase Transformation of NiTi

Department of Civil Engineering and Engineering Mechanics, University of Arizona, Tucson, AZ 85721, USA

Received 23 July 2016; Revised 7 September 2016; Accepted 18 September 2016

Academic Editor: Yong Liu

Copyright © 2016 Sourav Gur and George N. Frantziskonis. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The atomistic study shows strong size effects in thermally induced martensitic phase transformation evolution kinetics of equiatomic NiTi shape memory alloys (SMAs). It is shown that size effects are closely related to the presence of free surfaces; thus, NiTi thin films and nanopillars are studied. Quasi-static molecular dynamics simulations for several cell sizes at various (constant) temperatures are performed by employing well-established interatomic potentials for NiTi. The study shows that size plays a crucial role in the evolution of martensite phase fraction and, importantly, can significantly change the phase transformation temperatures, which can be used for the design of NiTi based sensors, actuators, or devices at nano- to microscales. Interestingly, it is found that, at the nanometer scale, Richard’s equation describes very well the martensite phase fraction evolution in NiTi thin films and nanopillars as a function of temperature.