Searching New Solutions for NiTi Sensors through Indirect Additive Manufacturing
Shape Memory Alloys (SMAs) can play an essential role in developing novel active sensors for self-healing, including aeronautical systems. However, the NiTi SMAs available in the market are almost limited to wires, small sheets, and coatings. This restriction is mainly due to the difficulty in proce...
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| Format: | Article |
| Language: | English |
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MDPI AG
2022-07-01
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| Series: | Materials |
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| Online Access: | https://www.mdpi.com/1996-1944/15/14/5007 |
| _version_ | 1797445553318002688 |
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| author | Pedro Carreira Daniel Gatões Nuno Alves Ana Sofia Ramos Maria Teresa Vieira |
| author_facet | Pedro Carreira Daniel Gatões Nuno Alves Ana Sofia Ramos Maria Teresa Vieira |
| author_sort | Pedro Carreira |
| collection | DOAJ |
| description | Shape Memory Alloys (SMAs) can play an essential role in developing novel active sensors for self-healing, including aeronautical systems. However, the NiTi SMAs available in the market are almost limited to wires, small sheets, and coatings. This restriction is mainly due to the difficulty in processing NiTi through conventional processes. Thus, the objective of this study is to evaluate the potential of one of the most promising routes for NiTi additive manufacturing—material extrusion (MEX). Optimizing the different steps during processing is mandatory to avoid brittle secondary phases formation, such as Ni<sub>3</sub>Ti. The prime NiTi powder is prealloyed, but it also contains NiTi<sub>2</sub> and Ni as secondary phases. The present study highlights the role of Ni and NiTi<sub>2</sub>, with the later having a melting temperature (Tm = 984 °C) lower than the NiTi sintering temperature, thus allowing a welcome liquid phase sintering (LPS). Nevertheless, the reaction of the liquid phase with the Ni phase could contribute to the formation of brittle intermetallic compounds, particularly around NiTi and NiTi<sub>2</sub> phases, affecting the final structural properties of the 3D object. The addition of TiH<sub>2</sub> to the virgin prealloyed NiTi powder was also studied and revealed the non-formation of Ni<sub>3</sub>Ti for a specific composition. The balancing addition of extra Ni revealed priority in the Ni<sub>3</sub>Ti appearance, emphasizing the role of Ni. Feedstocks extruded (filaments) and green strands (layers), before and after debinding & sintering, were used as homothetic of 3D objects for evaluation of defects (microtomography), microstructures, and mechanical properties. The composition of prealloyed powder with 5 wt.% TiH<sub>2</sub> addition after sintering showed a homogeneous matrix with the NiTi<sub>2</sub> second phase uniformly dispersed. |
| first_indexed | 2024-03-09T13:27:30Z |
| format | Article |
| id | doaj.art-a50a48f631ed4e56838c047877905759 |
| institution | Directory Open Access Journal |
| issn | 1996-1944 |
| language | English |
| last_indexed | 2024-03-09T13:27:30Z |
| publishDate | 2022-07-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Materials |
| spelling | doaj.art-a50a48f631ed4e56838c0478779057592023-11-30T21:22:28ZengMDPI AGMaterials1996-19442022-07-011514500710.3390/ma15145007Searching New Solutions for NiTi Sensors through Indirect Additive ManufacturingPedro Carreira0Daniel Gatões1Nuno Alves2Ana Sofia Ramos3Maria Teresa Vieira4CDRSP—Centre for Rapid and Sustainable Product Development, Polytechnic Institute of Leiria, 2411-901 Leiria, PortugalUniversity of Coimbra, CEMMPRE—Centre for Mechanical Engineering, Materials and Processes, Department of Mechanical Engineering, Polo II, R. Luís Reis Santos, 3030-788 Coimbra, PortugalCDRSP—Centre for Rapid and Sustainable Product Development, Polytechnic Institute of Leiria, 2411-901 Leiria, PortugalUniversity of Coimbra, CEMMPRE—Centre for Mechanical Engineering, Materials and Processes, Department of Mechanical Engineering, Polo II, R. Luís Reis Santos, 3030-788 Coimbra, PortugalUniversity of Coimbra, CEMMPRE—Centre for Mechanical Engineering, Materials and Processes, Department of Mechanical Engineering, Polo II, R. Luís Reis Santos, 3030-788 Coimbra, PortugalShape Memory Alloys (SMAs) can play an essential role in developing novel active sensors for self-healing, including aeronautical systems. However, the NiTi SMAs available in the market are almost limited to wires, small sheets, and coatings. This restriction is mainly due to the difficulty in processing NiTi through conventional processes. Thus, the objective of this study is to evaluate the potential of one of the most promising routes for NiTi additive manufacturing—material extrusion (MEX). Optimizing the different steps during processing is mandatory to avoid brittle secondary phases formation, such as Ni<sub>3</sub>Ti. The prime NiTi powder is prealloyed, but it also contains NiTi<sub>2</sub> and Ni as secondary phases. The present study highlights the role of Ni and NiTi<sub>2</sub>, with the later having a melting temperature (Tm = 984 °C) lower than the NiTi sintering temperature, thus allowing a welcome liquid phase sintering (LPS). Nevertheless, the reaction of the liquid phase with the Ni phase could contribute to the formation of brittle intermetallic compounds, particularly around NiTi and NiTi<sub>2</sub> phases, affecting the final structural properties of the 3D object. The addition of TiH<sub>2</sub> to the virgin prealloyed NiTi powder was also studied and revealed the non-formation of Ni<sub>3</sub>Ti for a specific composition. The balancing addition of extra Ni revealed priority in the Ni<sub>3</sub>Ti appearance, emphasizing the role of Ni. Feedstocks extruded (filaments) and green strands (layers), before and after debinding & sintering, were used as homothetic of 3D objects for evaluation of defects (microtomography), microstructures, and mechanical properties. The composition of prealloyed powder with 5 wt.% TiH<sub>2</sub> addition after sintering showed a homogeneous matrix with the NiTi<sub>2</sub> second phase uniformly dispersed.https://www.mdpi.com/1996-1944/15/14/5007Nickel-Titanium (NiTi)Shape Memory Alloys (SMAs)Metal Extrusion (MEX)additive manufacturing (AM)Titanium Hydride (TiH<sub>2</sub>) |
| spellingShingle | Pedro Carreira Daniel Gatões Nuno Alves Ana Sofia Ramos Maria Teresa Vieira Searching New Solutions for NiTi Sensors through Indirect Additive Manufacturing Materials Nickel-Titanium (NiTi) Shape Memory Alloys (SMAs) Metal Extrusion (MEX) additive manufacturing (AM) Titanium Hydride (TiH<sub>2</sub>) |
| title | Searching New Solutions for NiTi Sensors through Indirect Additive Manufacturing |
| title_full | Searching New Solutions for NiTi Sensors through Indirect Additive Manufacturing |
| title_fullStr | Searching New Solutions for NiTi Sensors through Indirect Additive Manufacturing |
| title_full_unstemmed | Searching New Solutions for NiTi Sensors through Indirect Additive Manufacturing |
| title_short | Searching New Solutions for NiTi Sensors through Indirect Additive Manufacturing |
| title_sort | searching new solutions for niti sensors through indirect additive manufacturing |
| topic | Nickel-Titanium (NiTi) Shape Memory Alloys (SMAs) Metal Extrusion (MEX) additive manufacturing (AM) Titanium Hydride (TiH<sub>2</sub>) |
| url | https://www.mdpi.com/1996-1944/15/14/5007 |
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