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Heat Treatments and Critical Quenching Rates in Additively Manufactured Al–Si–Mg Alloys
Laser powder-bed fusion (LPBF) has significantly gained in importance and has become one of the major fabrication techniques within metal additive manufacturing. The fast cooling rates achieved in LPBF due to a relatively small melt pool on a much larger component or substrate, acting as heat sink,...
Autores principales: | , , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
MDPI
2020
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7040918/ https://www.ncbi.nlm.nih.gov/pubmed/32033428 http://dx.doi.org/10.3390/ma13030720 |
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author | Hitzler, Leonhard Hafenstein, Stephan Mendez Martin, Francisca Clemens, Helmut Sert, Enes Öchsner, Andreas Merkel, Markus Werner, Ewald |
author_facet | Hitzler, Leonhard Hafenstein, Stephan Mendez Martin, Francisca Clemens, Helmut Sert, Enes Öchsner, Andreas Merkel, Markus Werner, Ewald |
author_sort | Hitzler, Leonhard |
collection | PubMed |
description | Laser powder-bed fusion (LPBF) has significantly gained in importance and has become one of the major fabrication techniques within metal additive manufacturing. The fast cooling rates achieved in LPBF due to a relatively small melt pool on a much larger component or substrate, acting as heat sink, result in fine-grained microstructures and high oversaturation of alloying elements in the α-aluminum. Al–Si–Mg alloys thus can be effectively precipitation hardened. Moreover, the solidified material undergoes an intrinsic heat treatment, whilst the layers above are irradiated and the elevated temperature in the built chamber starts the clustering process of alloying elements directly after a scan track is fabricated. These silicon–magnesium clusters were observed with atom probe tomography in as-built samples. Similar beneficial clustering behavior at higher temperatures is known from the direct-aging approach in cast samples, whereby the artificial aging is performed immediately after solution annealing and quenching. Transferring this approach to LPBF samples as a possible post-heat treatment revealed that even after direct aging, the outstanding hardness of the as-built condition could, at best, be met, but for most instances it was significantly lower. Our investigations showed that LPBF Al–Si–Mg exhibited a high dependency on the quenching rate, which is significantly more pronounced than in cast reference samples, requiring two to three times higher quenching rate after solution annealing to yield similar hardness results. This suggests that due to the finer microstructure and the shorter diffusion path in Al–Si–Mg fabricated by LPBF, it is more challenging to achieve a metastable oversaturation necessary for precipitation hardening. This may be especially problematic in larger components. |
format | Online Article Text |
id | pubmed-7040918 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2020 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-70409182020-03-09 Heat Treatments and Critical Quenching Rates in Additively Manufactured Al–Si–Mg Alloys Hitzler, Leonhard Hafenstein, Stephan Mendez Martin, Francisca Clemens, Helmut Sert, Enes Öchsner, Andreas Merkel, Markus Werner, Ewald Materials (Basel) Article Laser powder-bed fusion (LPBF) has significantly gained in importance and has become one of the major fabrication techniques within metal additive manufacturing. The fast cooling rates achieved in LPBF due to a relatively small melt pool on a much larger component or substrate, acting as heat sink, result in fine-grained microstructures and high oversaturation of alloying elements in the α-aluminum. Al–Si–Mg alloys thus can be effectively precipitation hardened. Moreover, the solidified material undergoes an intrinsic heat treatment, whilst the layers above are irradiated and the elevated temperature in the built chamber starts the clustering process of alloying elements directly after a scan track is fabricated. These silicon–magnesium clusters were observed with atom probe tomography in as-built samples. Similar beneficial clustering behavior at higher temperatures is known from the direct-aging approach in cast samples, whereby the artificial aging is performed immediately after solution annealing and quenching. Transferring this approach to LPBF samples as a possible post-heat treatment revealed that even after direct aging, the outstanding hardness of the as-built condition could, at best, be met, but for most instances it was significantly lower. Our investigations showed that LPBF Al–Si–Mg exhibited a high dependency on the quenching rate, which is significantly more pronounced than in cast reference samples, requiring two to three times higher quenching rate after solution annealing to yield similar hardness results. This suggests that due to the finer microstructure and the shorter diffusion path in Al–Si–Mg fabricated by LPBF, it is more challenging to achieve a metastable oversaturation necessary for precipitation hardening. This may be especially problematic in larger components. MDPI 2020-02-05 /pmc/articles/PMC7040918/ /pubmed/32033428 http://dx.doi.org/10.3390/ma13030720 Text en © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Article Hitzler, Leonhard Hafenstein, Stephan Mendez Martin, Francisca Clemens, Helmut Sert, Enes Öchsner, Andreas Merkel, Markus Werner, Ewald Heat Treatments and Critical Quenching Rates in Additively Manufactured Al–Si–Mg Alloys |
title | Heat Treatments and Critical Quenching Rates in Additively Manufactured Al–Si–Mg Alloys |
title_full | Heat Treatments and Critical Quenching Rates in Additively Manufactured Al–Si–Mg Alloys |
title_fullStr | Heat Treatments and Critical Quenching Rates in Additively Manufactured Al–Si–Mg Alloys |
title_full_unstemmed | Heat Treatments and Critical Quenching Rates in Additively Manufactured Al–Si–Mg Alloys |
title_short | Heat Treatments and Critical Quenching Rates in Additively Manufactured Al–Si–Mg Alloys |
title_sort | heat treatments and critical quenching rates in additively manufactured al–si–mg alloys |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7040918/ https://www.ncbi.nlm.nih.gov/pubmed/32033428 http://dx.doi.org/10.3390/ma13030720 |
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