Print Email Facebook Twitter Effect of Heat Treatment on Microstructure and Mechanical Behavior of Additively Manufactured Nitinol Shape Memory Alloys Title Effect of Heat Treatment on Microstructure and Mechanical Behavior of Additively Manufactured Nitinol Shape Memory Alloys Author Zhu, WEIJIA (TU Delft Mechanical, Maritime and Materials Engineering) Contributor Popovich, V. (mentor) Zhu, Jia-Ning (mentor) Hermans, M.J.M. (graduation committee) Degree granting institution Delft University of Technology Project Development of 4D Smart Metallic Materials produced by Additive Manufacturing Date 2021-10-06 Abstract Nitinol shape memory alloys (SMAs) have a unique combination of shape memory capability, making it an attractive material for various engineering and biomedical applications. Additive manufacturing (AM) by laser powder bed fusion (L-PBF) allows to produce Nitinol net shape parts, which broadens its applications. Due to the high heating and cooling rate during L-PBF process, there always exists supersaturated solute elements and metastable structures in L-PBF Nitinol parts. Microstructure and precipitate characteristics have detrimental effects on phase transformation and shape memory behavior of Nitinol alloys. Proper heat treatment is an important method to mitigate these detrimental effects and improve the properties of Nitinol. In this project, the effect of heat treatment on shape memory behavior of equiatomic Nitinol fabricated by L-PBF is studied. The heat treatment process is optimized, which is annealing at 950 °C for 5.5h and subsequent aging at 350 °C for 18 hours. By applying the optimized heat treatment process, the cyclic stability of the Ti50Ni50 SMA are improved by 50% for recoverable strain and 70 MPa for applied stress. Additionally, the relationship among the microstructure and precipitates, functional and mechanical properties, and heat treatment parameters are investigated. Subject laser powder bed fusionShape memory Alloyadditive manufacturingheat treatmentnitinolMechanical propertiesL-PBFphase transformationsPrecipitates To reference this document use: http://resolver.tudelft.nl/uuid:6823da64-0ac6-44a9-ab80-f97e84637b51 Embargo date 2023-10-05 Part of collection Student theses Document type master thesis Rights © 2021 WEIJIA Zhu Files PDF Final_thesis_Weijia_Zhu_5032601.pdf 5.23 MB Close viewer /islandora/object/uuid:6823da64-0ac6-44a9-ab80-f97e84637b51/datastream/OBJ/view