{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,28]],"date-time":"2026-01-28T12:23:14Z","timestamp":1769602994495,"version":"3.49.0"},"reference-count":41,"publisher":"MDPI AG","issue":"14","license":[{"start":{"date-parts":[[2022,7,19]],"date-time":"2022-07-19T00:00:00Z","timestamp":1658188800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"FEDER funds","award":["Project PTDC\/CTM-CTM\/29101\/2017\u2014POCI-01-0145-FEDER-029101"],"award-info":[{"award-number":["Project PTDC\/CTM-CTM\/29101\/2017\u2014POCI-01-0145-FEDER-029101"]}]},{"name":"FEDER funds","award":["UIDB\/EMS\/00285\/2020"],"award-info":[{"award-number":["UIDB\/EMS\/00285\/2020"]}]},{"name":"FEDER funds","award":["UIDB\/04044\/2020"],"award-info":[{"award-number":["UIDB\/04044\/2020"]}]},{"DOI":"10.13039\/501100001871","name":"FEDER funds","doi-asserted-by":"publisher","award":["Project PTDC\/CTM-CTM\/29101\/2017\u2014POCI-01-0145-FEDER-029101"],"award-info":[{"award-number":["Project PTDC\/CTM-CTM\/29101\/2017\u2014POCI-01-0145-FEDER-029101"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"FEDER funds","doi-asserted-by":"publisher","award":["UIDB\/EMS\/00285\/2020"],"award-info":[{"award-number":["UIDB\/EMS\/00285\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"FEDER funds","doi-asserted-by":"publisher","award":["UIDB\/04044\/2020"],"award-info":[{"award-number":["UIDB\/04044\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"name":"FEDER funds","award":["Project PTDC\/CTM-CTM\/29101\/2017\u2014POCI-01-0145-FEDER-029101"],"award-info":[{"award-number":["Project PTDC\/CTM-CTM\/29101\/2017\u2014POCI-01-0145-FEDER-029101"]}]},{"name":"FEDER funds","award":["UIDB\/EMS\/00285\/2020"],"award-info":[{"award-number":["UIDB\/EMS\/00285\/2020"]}]},{"name":"FEDER funds","award":["UIDB\/04044\/2020"],"award-info":[{"award-number":["UIDB\/04044\/2020"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>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\u2014material extrusion (MEX). Optimizing the different steps during processing is mandatory to avoid brittle secondary phases formation, such as Ni3Ti. The prime NiTi powder is prealloyed, but it also contains NiTi2 and Ni as secondary phases. The present study highlights the role of Ni and NiTi2, with the later having a melting temperature (Tm = 984 \u00b0C) 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 NiTi2 phases, affecting the final structural properties of the 3D object. The addition of TiH2 to the virgin prealloyed NiTi powder was also studied and revealed the non-formation of Ni3Ti for a specific composition. The balancing addition of extra Ni revealed priority in the Ni3Ti appearance, emphasizing the role of Ni. Feedstocks extruded (filaments) and green strands (layers), before and after debinding &amp; 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.% TiH2 addition after sintering showed a homogeneous matrix with the NiTi2 second phase uniformly dispersed.<\/jats:p>","DOI":"10.3390\/ma15145007","type":"journal-article","created":{"date-parts":[[2022,7,19]],"date-time":"2022-07-19T05:37:53Z","timestamp":1658209073000},"page":"5007","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Searching New Solutions for NiTi Sensors through Indirect Additive Manufacturing"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4698-3650","authenticated-orcid":false,"given":"Pedro","family":"Carreira","sequence":"first","affiliation":[{"name":"CDRSP\u2014Centre for Rapid and Sustainable Product Development, Polytechnic Institute of Leiria, 2411-901 Leiria, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8078-6530","authenticated-orcid":false,"given":"Daniel","family":"Gat\u00f5es","sequence":"additional","affiliation":[{"name":"University of Coimbra, CEMMPRE\u2014Centre for Mechanical Engineering, Materials and Processes, Department of Mechanical Engineering, Polo II, R. Lu\u00eds Reis Santos, 3030-788 Coimbra, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5016-0868","authenticated-orcid":false,"given":"Nuno","family":"Alves","sequence":"additional","affiliation":[{"name":"CDRSP\u2014Centre for Rapid and Sustainable Product Development, Polytechnic Institute of Leiria, 2411-901 Leiria, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8486-5436","authenticated-orcid":false,"given":"Ana Sofia","family":"Ramos","sequence":"additional","affiliation":[{"name":"University of Coimbra, CEMMPRE\u2014Centre for Mechanical Engineering, Materials and Processes, Department of Mechanical Engineering, Polo II, R. Lu\u00eds Reis Santos, 3030-788 Coimbra, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9981-3826","authenticated-orcid":false,"given":"Maria Teresa","family":"Vieira","sequence":"additional","affiliation":[{"name":"University of Coimbra, CEMMPRE\u2014Centre for Mechanical Engineering, Materials and Processes, Department of Mechanical Engineering, Polo II, R. Lu\u00eds Reis Santos, 3030-788 Coimbra, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2022,7,19]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1475","DOI":"10.1063\/1.1729603","article-title":"Effect of Low-Temperature Phase Changes on the Mechanical Properties of Alloys near Composition TiNi","volume":"34","author":"Buehler","year":"1963","journal-title":"J. Appl. Phys."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"511","DOI":"10.1016\/j.pmatsci.2004.10.001","article-title":"Physical metallurgy of Ti\u2013Ni-based Shape Memory Alloys","volume":"50","author":"Otsuka","year":"2005","journal-title":"Prog. Mater. Sci."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Walker, J., Elahinia, M., and Haberland, C. (2013, January 16\u201318). An investigation of process parameters on selective laser melting of nitinol. Proceedings of the ASME 2013 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, Snowbird, UT, USA.","DOI":"10.1115\/SMASIS2013-3074"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"653","DOI":"10.1016\/j.jmrt.2022.05.076","article-title":"Machining parameter optimization and experimental investigations of nano-graphene mixed electrical discharge machining of nitinol shape memory alloy","volume":"19","author":"Vora","year":"2022","journal-title":"J. Mater. Res. Technol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"241","DOI":"10.1016\/j.jmrt.2021.04.058","article-title":"Study on properties of SLM-NiTi shape memory alloy under the same energy density","volume":"13","author":"Yu","year":"2021","journal-title":"J. Mater. Res. Technol."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Chmielewska, A., Wysocki, B., Kwa\u015bniak, P., Kruszewski, M.J., Michalski, B., Zieli\u0144ska, A., Adamczyk-Cie\u015blak, B., Krawczy\u0144ska, A., Buhagiar, J., and \u015awi\u0119szkowski, W. (2022). Heat Treatment of NiTi Alloys Fabricated Using Laser Powder Bed Fusion (LPBF) from Elementally Blended Powders. Materials, 15.","DOI":"10.3390\/ma15093304"},{"key":"ref_7","unstructured":"(2021). Additive Manufacturing\u2014General Principles\u2014Fundamentals and Vocabulary (Standard No. ISO\/ASTM 52900)."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Carreira, P., Cerejo, F., Alves, N., and Vieira, M. (2020). In Search of the Optimal Conditions to Process Shape Memory Alloys (NiTi) Using Fused Filament Fabrication (FFF). Materials, 13.","DOI":"10.3390\/ma13214718"},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Suwanpreecha, C., and Manonukul, A. (2022). A Review on Material Extrusion Additive Manufacturing of Metal and How It Compares with Metal Injection Moulding. Metals, 12.","DOI":"10.3390\/met12030429"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"2949","DOI":"10.1007\/s11661-017-4043-8","article-title":"Dehydrogenation and Sintering of TiH2: An In Situ Study","volume":"48","author":"Chen","year":"2017","journal-title":"Metall. Mater. Trans. A"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"117","DOI":"10.1016\/j.msea.2013.05.082","article-title":"Porous NiTi alloys produced by press-and-sinter from Ni\/Ti and Ni\/TiH2 mixtures","volume":"582","author":"Chen","year":"2013","journal-title":"Mater. Sci. Eng. A"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"5118","DOI":"10.1007\/s11665-017-2957-3","article-title":"Fabrication and Properties of Porous NiTi Alloy by Gel-Casting with TiH2 Powders","volume":"26","author":"Bohua","year":"2017","journal-title":"J. Mater. Eng. Perform."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"190","DOI":"10.1016\/S0921-5093(03)00117-5","article-title":"Dehydrogenation of TiH2","volume":"356","author":"Bhosle","year":"2003","journal-title":"Mater. Sci. Eng. A"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"530","DOI":"10.3390\/met5020530","article-title":"An in situ Study of NiTi Powder Sintering Using Neutron Diffraction","volume":"5","author":"Chen","year":"2015","journal-title":"Metals"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"228","DOI":"10.1007\/s11665-017-3099-3","article-title":"Porous Titanium Parts Fabricated by Sintering of TiH2 and Ti Powder Mixtures","volume":"27","author":"Peng","year":"2017","journal-title":"J. Mater. Eng. Perform."},{"key":"ref_16","unstructured":"Sun, P., Wang, H., Lefler, M., Fang, Z., Lei, T., Fang, S., Tian, W., and Li, H. (2010, January 10\u201314). Sintering of TiH2\u2014A new approach for powder metallurgy titanium. Proceedings of the World Powder Metallurgy Congress and Exhibition, Florence, Italy."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"70","DOI":"10.1016\/S0921-5093(98)00780-1","article-title":"Anisotropy of dimensional change and its corresponding improvement by addition of TiH2 during elemental powder sintering of porous NiTi alloy","volume":"255","author":"Li","year":"1998","journal-title":"Mater. Sci. Eng. A"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"169","DOI":"10.1016\/S0921-5093(99)00729-7","article-title":"The influence of addition of TiH2 in elemental powder sintering porous Ni\u2013Ti alloys","volume":"281","author":"Li","year":"2000","journal-title":"Mater. Sci. Eng. A"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"143","DOI":"10.1016\/S0921-5093(04)00837-8","article-title":"Powder sintering and shape-memory behaviour of NiTi compacts synthesized from Ni and TiH2","volume":"384","author":"Bertheville","year":"2004","journal-title":"Mater. Sci. Eng. A"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"32","DOI":"10.1016\/j.actamat.2013.12.013","article-title":"In situ observation and neutron diffraction of NiTi powder sintering","volume":"67","author":"Chen","year":"2014","journal-title":"Acta Mater."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Wang, J. (2012). Powder Injection Molding of Metal and Ceramic Parts. Some Critical Issues for Injection Molding, InTech.","DOI":"10.5772\/2294"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"768","DOI":"10.1016\/j.matdes.2015.06.053","article-title":"Fused deposition modeling with polypropylene","volume":"83","author":"Carneiro","year":"2015","journal-title":"Mater. Des."},{"key":"ref_23","unstructured":"Heaney, D.F. (2012). Handbook of Metal Injection Molding, Woodhead Publishing. Woodhead Publishing in Materials."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"18","DOI":"10.1016\/S0026-0657(09)70215-2","article-title":"Fine tuning injection feedstock by nano coating SS powder","volume":"64","author":"Barreiros","year":"2009","journal-title":"Met. Powder Rep."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"651","DOI":"10.1016\/j.jmatprotec.2007.11.162","article-title":"Surface modification of stainless steel powders for microfabrication","volume":"201","author":"Vieira","year":"2008","journal-title":"J. Mater. Process. Technol."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"2449","DOI":"10.1007\/s00170-021-07043-0","article-title":"Optimization of metallic powder filaments for additive manufacturing extrusion (MEX)","volume":"115","author":"Cerejo","year":"2021","journal-title":"Int. J. Adv. Manuf. Technol."},{"key":"ref_27","unstructured":"Dassault, S. (2019, May 10). Solidworks Student Version. Available online: https:\/\/www.3ds.com\/products-services\/solidworks\/."},{"key":"ref_28","unstructured":"Ultimaker, B.V. (2019, March 05). Ultimaker Cura 4.1. Available online: https:\/\/ultimaker.com\/en\/products\/ultimaker-cura-software."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"2701","DOI":"10.1007\/s11665-012-0264-6","article-title":"Reproducibility Study of NiTi Parts Made by Metal Injection Molding","volume":"21","author":"Bram","year":"2012","journal-title":"J. Mater. Eng. Perform."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"522","DOI":"10.1007\/s11665-011-9854-y","article-title":"Mechanical Properties of Highly Porous NiTi Alloys","volume":"20","author":"Bram","year":"2011","journal-title":"J. Mater. Eng. Perform."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"4231","DOI":"10.1007\/s10853-005-2819-5","article-title":"Metal injection molding of Shape Memory Alloys using prealloyed NiTi powders","volume":"40","author":"Krone","year":"2005","journal-title":"J. Mater. Sci."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"173","DOI":"10.4028\/www.scientific.net\/KEM.704.173","article-title":"Metal Injection Moulding of Superelastic TiNi Parts","volume":"704","author":"Bidaux","year":"2016","journal-title":"Key Eng. Mater."},{"key":"ref_33","unstructured":"Fang, Z.Z. (2010). Sintering of Advanced Materials\u2014Fundamentals and Processes, Woodhead Publishing. [1st ed.]."},{"key":"ref_34","first-page":"4299","article-title":"Prepare Nitinol Alloys and Improve their Hardness Using Copper as an Alloying Element","volume":"12","author":"Alnomani","year":"2017","journal-title":"Int. J. Appl. Eng. Res."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"3582","DOI":"10.1016\/j.actamat.2010.02.028","article-title":"Genetic design and characterization of novel ultra-high-strength stainless steels strengthened by Ni3Ti intermetallic nanoprecipitates","volume":"58","author":"Xu","year":"2010","journal-title":"Acta Mater."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"91","DOI":"10.1016\/j.vacuum.2011.04.022","article-title":"Characterization and corrosion behavior of NiTi\u2013Ti2Ni\u2013Ni3Ti multiphase intermetallics produced by vacuum sintering","volume":"86","author":"Verdian","year":"2011","journal-title":"Vacuum"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"107119","DOI":"10.1016\/j.intermet.2021.107119","article-title":"Microstructural characterization and enhanced hardness of nanostructured Ni3Ti\u2013NiTi (B2) intermetallic alloy produced by mechanical alloying and fast microwave-assisted sintering process","volume":"131","author":"Akbarpour","year":"2021","journal-title":"Intermetallics"},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Feng, Y., Du, Z., and Hu, Z. (2021). Study on the Effect of Ni Addition on the Microstructure and Properties of NiTi Alloy Coating on AISI 316 L Prepared by Laser Cladding. Materials, 14.","DOI":"10.3390\/ma14164373"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"84","DOI":"10.4236\/wjet.2015.33C013","article-title":"Microstructure and Mechanical Properties of NiTi2-TiB Composite Fabricated by Spark Plasma Sintering","volume":"3","author":"Yoshida","year":"2015","journal-title":"World J. Eng. Technol."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"126","DOI":"10.1016\/S0921-5093(02)00076-X","article-title":"Microstructure and wear resistance of laser clad Ti5Si3\/NiTi2 intermetallic composite coating on titanium alloy","volume":"338","author":"Wang","year":"2002","journal-title":"Mater. Sci. Eng. A"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"3315","DOI":"10.1016\/S1003-6326(15)63989-9","article-title":"In situ laser deposition of NiTi intermetallics for corrosion improvement of Ti\u20136Al\u20134V alloy","volume":"25","author":"Mokgalaka","year":"2015","journal-title":"Trans. Nonferrous Met. Soc. China"}],"container-title":["Materials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1996-1944\/15\/14\/5007\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T23:53:34Z","timestamp":1760140414000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1996-1944\/15\/14\/5007"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,7,19]]},"references-count":41,"journal-issue":{"issue":"14","published-online":{"date-parts":[[2022,7]]}},"alternative-id":["ma15145007"],"URL":"https:\/\/doi.org\/10.3390\/ma15145007","relation":{},"ISSN":["1996-1944"],"issn-type":[{"value":"1996-1944","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,7,19]]}}}