Resultant physical properties of as-built nitinol processed at specific volumetric energy densities and correlation with in-situ melt pool temperatures
In this study, direct comparisons between the properties of three groups of as-built nitinol (NiTi) samples fabricated using three pre-determined volumetric energy densities (VED) as calculated based on hatch spacings (VEDH = 40, 80, and 120 J/mm3), were examined. The additive manufacturing techniqu...
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| Format: | Article |
| Language: | English |
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Elsevier
2022-11-01
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| Series: | Journal of Materials Research and Technology |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S223878542201612X |
| _version_ | 1798006092257558528 |
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| author | Medad C.C. Monu Emmanuel J. Ekoi Cian Hughes Sujith Kumar S. Dermot Brabazon |
| author_facet | Medad C.C. Monu Emmanuel J. Ekoi Cian Hughes Sujith Kumar S. Dermot Brabazon |
| author_sort | Medad C.C. Monu |
| collection | DOAJ |
| description | In this study, direct comparisons between the properties of three groups of as-built nitinol (NiTi) samples fabricated using three pre-determined volumetric energy densities (VED) as calculated based on hatch spacings (VEDH = 40, 80, and 120 J/mm3), were examined. The additive manufacturing technique adopted is the powder bed fusion using a laser beam (PBF-LB), and the powder feedstock is Ni50Ti50. Although the three VEDH's increased by 100% for each sample group, each VEDH value was within the range of those recommended in the literature, as well as equivalent to 100 J/mm3 (VEDf), VED as calculated based on laser spot size. Significant differences were found between the thermal profiles and normalised thermal gradients, resulting in compositional differences, defects, phase, and phase transformation behaviour, Young's modulus, hardness, and microstructure. Thermal gradients and full-wave amplitude of the in-situ melt pool thermal radiation waveforms increased as VEDH increased. Higher VEDH's resulted in more martensitic NiTi samples with larger melt pool volume and >98% sample relative density. Austenite transformation temperatures increased with an increase in at.% Ti for each increase in VEDH, consequent on the higher normalised average melt pool temperatures. The calculated thermal gradient (normalised) was correlated to higher thermal stresses as VEDH increased, resulting in residual stress-induced weld-metal liquation microcracks. This work has demonstrated the potential of post-processed in-situ melt pool thermal radiation data, in providing insights into the physical property variations of as-built nitinol samples fabricated via PBF-LB. |
| first_indexed | 2024-04-11T12:49:30Z |
| format | Article |
| id | doaj.art-347c64919d4742498206b0605597a946 |
| institution | Directory Open Access Journal |
| issn | 2238-7854 |
| language | English |
| last_indexed | 2024-04-11T12:49:30Z |
| publishDate | 2022-11-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Journal of Materials Research and Technology |
| spelling | doaj.art-347c64919d4742498206b0605597a9462022-12-22T04:23:14ZengElsevierJournal of Materials Research and Technology2238-78542022-11-012127572777Resultant physical properties of as-built nitinol processed at specific volumetric energy densities and correlation with in-situ melt pool temperaturesMedad C.C. Monu0Emmanuel J. Ekoi1Cian Hughes2Sujith Kumar S.3Dermot Brabazon4I-Form Advanced Manufacturing Research Center, Dublin City University, Dublin, Ireland; School of Mechanical and Manufacturing Engineering, Dublin City University, Dublin, Ireland; Advanced Processing Technology Research Center, Dublin City University, Dublin, Ireland; Corresponding author.I-Form Advanced Manufacturing Research Center, Dublin City University, Dublin, Ireland; School of Mechanical and Manufacturing Engineering, Dublin City University, Dublin, Ireland; Advanced Processing Technology Research Center, Dublin City University, Dublin, IrelandI-Form Advanced Manufacturing Research Center, Dublin City University, Dublin, Ireland; School of Mechanical and Manufacturing Engineering, Dublin City University, Dublin, IrelandI-Form Advanced Manufacturing Research Center, Dublin City University, Dublin, Ireland; School of Mechanical and Manufacturing Engineering, Dublin City University, Dublin, IrelandI-Form Advanced Manufacturing Research Center, Dublin City University, Dublin, Ireland; School of Mechanical and Manufacturing Engineering, Dublin City University, Dublin, Ireland; Advanced Processing Technology Research Center, Dublin City University, Dublin, IrelandIn this study, direct comparisons between the properties of three groups of as-built nitinol (NiTi) samples fabricated using three pre-determined volumetric energy densities (VED) as calculated based on hatch spacings (VEDH = 40, 80, and 120 J/mm3), were examined. The additive manufacturing technique adopted is the powder bed fusion using a laser beam (PBF-LB), and the powder feedstock is Ni50Ti50. Although the three VEDH's increased by 100% for each sample group, each VEDH value was within the range of those recommended in the literature, as well as equivalent to 100 J/mm3 (VEDf), VED as calculated based on laser spot size. Significant differences were found between the thermal profiles and normalised thermal gradients, resulting in compositional differences, defects, phase, and phase transformation behaviour, Young's modulus, hardness, and microstructure. Thermal gradients and full-wave amplitude of the in-situ melt pool thermal radiation waveforms increased as VEDH increased. Higher VEDH's resulted in more martensitic NiTi samples with larger melt pool volume and >98% sample relative density. Austenite transformation temperatures increased with an increase in at.% Ti for each increase in VEDH, consequent on the higher normalised average melt pool temperatures. The calculated thermal gradient (normalised) was correlated to higher thermal stresses as VEDH increased, resulting in residual stress-induced weld-metal liquation microcracks. This work has demonstrated the potential of post-processed in-situ melt pool thermal radiation data, in providing insights into the physical property variations of as-built nitinol samples fabricated via PBF-LB.http://www.sciencedirect.com/science/article/pii/S223878542201612XVolumetric energy densityNiTi alloysIn-situ monitoringResidual stressesLaser powder bed fusionLiquation cracking |
| spellingShingle | Medad C.C. Monu Emmanuel J. Ekoi Cian Hughes Sujith Kumar S. Dermot Brabazon Resultant physical properties of as-built nitinol processed at specific volumetric energy densities and correlation with in-situ melt pool temperatures Journal of Materials Research and Technology Volumetric energy density NiTi alloys In-situ monitoring Residual stresses Laser powder bed fusion Liquation cracking |
| title | Resultant physical properties of as-built nitinol processed at specific volumetric energy densities and correlation with in-situ melt pool temperatures |
| title_full | Resultant physical properties of as-built nitinol processed at specific volumetric energy densities and correlation with in-situ melt pool temperatures |
| title_fullStr | Resultant physical properties of as-built nitinol processed at specific volumetric energy densities and correlation with in-situ melt pool temperatures |
| title_full_unstemmed | Resultant physical properties of as-built nitinol processed at specific volumetric energy densities and correlation with in-situ melt pool temperatures |
| title_short | Resultant physical properties of as-built nitinol processed at specific volumetric energy densities and correlation with in-situ melt pool temperatures |
| title_sort | resultant physical properties of as built nitinol processed at specific volumetric energy densities and correlation with in situ melt pool temperatures |
| topic | Volumetric energy density NiTi alloys In-situ monitoring Residual stresses Laser powder bed fusion Liquation cracking |
| url | http://www.sciencedirect.com/science/article/pii/S223878542201612X |
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