Title
Effect of heat treatment on microstructure and functional properties of additively manufactured NiTi shape memory alloys
Author
Zhu, Jia-Ning (TU Delft Team Vera Popovich)
Zhu, Weijia (Student TU Delft)
Borisov, Evgenii (Peter the Great Saint-Petersburg Polytechnic University)
Yao, Xiyu (Southern University of Science and Technology of China)
Riemslag, A.C. (TU Delft Team Vera Popovich)
Goulas, Constantinos (University of Twente)
Popovich, Anatoly (Peter the Great Saint-Petersburg Polytechnic University)
Yan, Z. (TU Delft Team Vera Popovich)
Tichelaar, F.D. (TU Delft QN/Afdelingsbureau; Kavli institute of nanoscience Delft) 
Mainali, D.P. (TU Delft Team Maria Santofimia Navarro)
Hermans, M.J.M. (TU Delft Team Marcel Hermans)
Popovich, V. (TU Delft Team Vera Popovich)
Date
2023
Abstract
Additive manufacturing of NiTi shape memory alloys has attracted attention in recent years, due to design flexibility and feasibility to achieve four-dimensional (4D) function response. To obtain customized 4D functional responses in NiTi structures, tailorable phase transformation temperatures and stress windows as well as one-way or two-way shape memory properties are required. To achieve this goal, various heat treatments, including direct aging, annealing and annealing followed by aging, were optimized for the Ti-rich NiTi (Ni49.6Ti (at. %)) fabricated by laser powder bed fusion (L-PBF). Microstructural evolution, phase transformation, precipitation and shape memory behaviour were systematically investigated by multiscale correlative microstructural, differential scanning calorimetry analysis and thermomechanical analysis. Based on optimized heat treatments, ∼25 K phase transformation temperature windows and ∼90 MPa stress windows were achieved for the one-way shape memory effect. Solutionized annealing was found to be the most effective way to improve one-way shape memory degradation resistance, due to the reduction of defects and solid solution strengthening. One of the main findings of this study is that the heterogonous microstructures between hard intergranular Ti2NiOx and soft NiTi matrix, induced by solutionized annealing with subsequent aging, result in strain partitioning and enclosing the internal stress state, which was found to promote a pronounced two-way shape memory effect response. The results of this work provide in-depth knowledge on tailoring and designing functional shape memory characteristics via heat treatments, which contributes to expanding L-PBF NiTi application fields, such as biomedical implants, aerospace components, and other advanced engineering applications.
Subject
Heat treatment
Laser powder bed fusion
Microstructure
NiTi alloys
Shape memory effect
To reference this document use:
http://resolver.tudelft.nl/uuid:f7cb8551-145f-42c1-801c-869747c4b07a
DOI
https://doi.org/10.1016/j.jallcom.2023.171740
ISSN
0925-8388
Source
Journal of Alloys and Compounds, 967
Part of collection
Institutional Repository
Document type
journal article
Rights
© 2023 Jia-Ning Zhu, Weijia Zhu, Evgenii Borisov, Xiyu Yao, A.C. Riemslag, Constantinos Goulas, Anatoly Popovich, Z. Yan, F.D. Tichelaar, D.P. Mainali, M.J.M. Hermans, V. Popovich