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Advances in Materials Science and Engineering
Volume 2015 (2015), Article ID 434923, 7 pages
http://dx.doi.org/10.1155/2015/434923
Research Article

Improvement in the Mechanical Properties of High Temperature Shape Memory Alloy (Ti50Ni25Pd25) by Copper Addition

1School of Mechanical and Manufacturing Engineering (SMME), National University of Science and Technology (NUST), Islamabad 44000, Pakistan
2Institute of Industrial Control System, Rawalpindi 46000, Pakistan

Received 28 November 2014; Accepted 20 February 2015

Academic Editor: Rui Vilar

Copyright © 2015 Saif ur Rehman et al. 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

High temperature shape memory alloys Ti50Ni25Pd25 and Ti50Ni20Pd25Cu5 were developed, characterized, and tensile tested in both martensite ( − 50°C) and austenite ( + 50°C) phases. The transformation temperatures of ternary Ti50Ni25Pd25 alloy were increased by 11 to 12.5°C by substitution of Ni with 5 at% Cu. At the same time, transformation heat absorbed and released during forward and reverse martensitic transformation was also increased. In the martensite phase, the mechanical properties, that is, the stress for reorientation of martensite variants and fracture stress, were increased by 33 and 60 MPa, respectively, whereas the fracture strain was decreased by 1.5%. In the austenite phase, the critical stress for slip and fracture stress were increased by 62 and 40.9 MPa, respectively, whereas the fracture strain was decreased by 1.2%. The increase in both stresses was attributed to the solid solution strengthening by substitution of Ni atoms with relatively greater atomic radius of copper (Cu) atoms. The overall results suggest that the addition of 5 at% Cu in place of Ni in Ti50Ni25Pd25 alloy is very beneficial to improving the mechanical and shape memory properties and increasing the transformation temperatures.