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Advances in Materials Science and Engineering
Volume 2008, Article ID 659145, 5 pages
http://dx.doi.org/10.1155/2008/659145
Research Article

Thermal Arrest Memory Effect in Ni-Mn-Ga Alloys

Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 12116 Praha 2, Czech Republic

Received 22 May 2008; Accepted 21 October 2008

Academic Editor: Paul Munroe

Copyright © 2008 A. Rudajevova. 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

Dilatation characteristics were measured to investigate the thermal arrest memory effect in and alloys. Interruption of the martensite-austenite phase transformation is connected with the reduction of the sample length after thermal cycle. If a total phase transformation took place in the complete thermal cycle following the interruption, then the sample length would return to its original length. Analysis of these results has shown that the thermal arrest memory effect is a consequence of a stress-focusing effect and shape memory effect. The stress-focusing effect occurs when the phase transformation propagates radially in a cylindrical sample from the surface, inward to the center. Evolution and release of the thermoelastic deformations in both alloys during heating and cooling are analyzed.