Partial Transformation and the Two-Way Shape Recovery CharacteristicsWada K*
College of Engineering, Swansea University, United Kingdom
- *Corresponding Author:
- Wada K
College of Engineering
Swansea University, Bay Campus, Crymlyn Burrows
Swansea SA1 8EN, United Kingdom
E-mail: [email protected]
Received Date: May 19, 2016; Accepted Date: June 01, 2016; Published Date: June 11, 2016
Citation: Wada K (2016) Partial Transformation and the Two-Way Shape Recovery Characteristics. J Material Sci Eng 5:262. doi:10.4172/2169-0022.1000262
Copyright: © 2016 Wada K. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
It is widely known that two-way memory effect (TWME) is not an inherent property of shape memory alloy. The development of TWME requires thermomechanical training. Experimental study showed that undergoing partial reverse transformation in the course of training leads to the emergence of temporal two-step transformation, which was traditionally observed in the calorimetry measurement of an arrested stress-free heating cycle. The present work introduces a macromechanical approach to explain the mechanism of two-step transformation and its associated effects on stress-assisted two-way memory effect (SATWME) and TWME. The appearance of two-step transformation was observed to be a one-time only phenomenon and it clearly disappeared in the next full transformation. The disappearance of two-step transformation highlighted the occurrence of microstructural rearrangement driven by the internal stress field in the successive training cycles. A strain comparison demonstrated that the dominance of retransforming stress-assisted martensite (SAM) during cooling promoted the formation of internal back stress. This makes the accommodation process of deformation-induced martensite generated via pre-straining and SAM difficult, owing to which immobilizes the dislocations movement in the forward transformation direction, and causes detrimental effect on the TWME.