Publicação
Development and Characterization of Titanium Alloys Processed by Laser Powder Bed Fusion for Biomedical Applications
| Resumo: | This work focuses on the development and characterization of two titanium alloys: Ti-6Al-4V Extra Low Interstitial (Ti-64 ELI) and Ti-35Nb-7Zr-5Ta (TNZT) - α+β and β, respectively, both processed using Laser Powder Bed Fusion (LPBF), an Additive Manufacturing (AM) technology, for biomedical applications. In the first phase, both alloys were characterized in their powder form using techniques like optical microscopy, X-ray diffraction, sieving, and flowability tests to evaluate particle size, morphology, and metallic phases. Ti-64 ELI exhibited smaller, more spherical particles with better flowability than TNZT. The second phase involved optimizing the LPBF process parameters (laser power, scan speed, and hatch spacing) for Ti-64 ELI. Various Design of Experiments (DoE) were conducted to maximize properties such as density, minimize defects like porosity and surface roughness. Different regions of the printed parts (fill hatch, supports, upskin/downskin surfaces, borders and thin walls) were optimized separately, leading to parameter sets that produced defect-free, highdensity parts with minimized surface roughness. Furthermore, the impact of build platform temperature on residual stress was studied using cantilever geometries, revealing that higher temperatures reduced stress-induced deformations. Subsequently, TNZT alloy was optimized using similar methodologies, achieving high-density parts with the parameter set (1000 W, 0.09 mm hatch spacing, and 250 mm/s scan speed). Finally, two scanning strategies, meander and stripes, were evaluated for Ti-6Al-4V, focusing on their effects on roughness, hardness, microstructure, and phase constitution. Results showed that meander, with rotation angles between layers, performed better in terms of thermal history control and final part quality. |
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| Autores principais: | Carvalho, André Tiago Rodrigues |
| Assunto: | Fabrico Aditivo Fusão a Laser em Cama de Pó Ligas de Titânio Optimização Aplicações Biomédicas Teses de mestrado - 2024 |
| Ano: | 2024 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | This work focuses on the development and characterization of two titanium alloys: Ti-6Al-4V Extra Low Interstitial (Ti-64 ELI) and Ti-35Nb-7Zr-5Ta (TNZT) - α+β and β, respectively, both processed using Laser Powder Bed Fusion (LPBF), an Additive Manufacturing (AM) technology, for biomedical applications. In the first phase, both alloys were characterized in their powder form using techniques like optical microscopy, X-ray diffraction, sieving, and flowability tests to evaluate particle size, morphology, and metallic phases. Ti-64 ELI exhibited smaller, more spherical particles with better flowability than TNZT. The second phase involved optimizing the LPBF process parameters (laser power, scan speed, and hatch spacing) for Ti-64 ELI. Various Design of Experiments (DoE) were conducted to maximize properties such as density, minimize defects like porosity and surface roughness. Different regions of the printed parts (fill hatch, supports, upskin/downskin surfaces, borders and thin walls) were optimized separately, leading to parameter sets that produced defect-free, highdensity parts with minimized surface roughness. Furthermore, the impact of build platform temperature on residual stress was studied using cantilever geometries, revealing that higher temperatures reduced stress-induced deformations. Subsequently, TNZT alloy was optimized using similar methodologies, achieving high-density parts with the parameter set (1000 W, 0.09 mm hatch spacing, and 250 mm/s scan speed). Finally, two scanning strategies, meander and stripes, were evaluated for Ti-6Al-4V, focusing on their effects on roughness, hardness, microstructure, and phase constitution. Results showed that meander, with rotation angles between layers, performed better in terms of thermal history control and final part quality. |
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