Cargando…
New Grain Formation by Constitutional Undercooling Due to Remelting of Segregated Microstructures during Powder Bed Fusion
A microstructure has significant influence on the mechanical properties of parts. For isotropic properties, the formation of equiaxed microstructures by the nucleation of new grains during solidification is necessary. For conventional solidification processes, nucleation is well-understood. Regardin...
Autores principales: | , , , , |
---|---|
Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
MDPI
2020
|
Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7731160/ https://www.ncbi.nlm.nih.gov/pubmed/33287217 http://dx.doi.org/10.3390/ma13235517 |
_version_ | 1783621845758509056 |
---|---|
author | Rausch, Alexander M. Gotterbarm, Martin R. Pistor, Julian Markl, Matthias Körner, Carolin |
author_facet | Rausch, Alexander M. Gotterbarm, Martin R. Pistor, Julian Markl, Matthias Körner, Carolin |
author_sort | Rausch, Alexander M. |
collection | PubMed |
description | A microstructure has significant influence on the mechanical properties of parts. For isotropic properties, the formation of equiaxed microstructures by the nucleation of new grains during solidification is necessary. For conventional solidification processes, nucleation is well-understood. Regarding powder bed fusion, the repeated remelting of previous layers can cause nucleation under some conditions that are not explainable with classical theories. Here, we investigate this nucleation mechanism with an unprecedented level of detail. In the first step, we built samples with single crystalline microstructures from Ni-base superalloy IN718 by selective electron beam melting. In the second step, single lines with different parameters were molten on top of these samples. We observed a huge number of new grains by nucleation at the melt-pool border of these single lines. However, new grains can only prevail if the alignment of their crystallographic orientation with respect to the local temperature gradient is superior to that of the base material. The current hypothesis is that nucleation at the melt-pool border happens due to remelting microsegregations from former solidification processes leading to constitutional undercooling directly at the onset of solidification. This study offers the opportunity to understand and exploit this mechanism for different manufacturing processes. |
format | Online Article Text |
id | pubmed-7731160 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2020 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-77311602020-12-12 New Grain Formation by Constitutional Undercooling Due to Remelting of Segregated Microstructures during Powder Bed Fusion Rausch, Alexander M. Gotterbarm, Martin R. Pistor, Julian Markl, Matthias Körner, Carolin Materials (Basel) Article A microstructure has significant influence on the mechanical properties of parts. For isotropic properties, the formation of equiaxed microstructures by the nucleation of new grains during solidification is necessary. For conventional solidification processes, nucleation is well-understood. Regarding powder bed fusion, the repeated remelting of previous layers can cause nucleation under some conditions that are not explainable with classical theories. Here, we investigate this nucleation mechanism with an unprecedented level of detail. In the first step, we built samples with single crystalline microstructures from Ni-base superalloy IN718 by selective electron beam melting. In the second step, single lines with different parameters were molten on top of these samples. We observed a huge number of new grains by nucleation at the melt-pool border of these single lines. However, new grains can only prevail if the alignment of their crystallographic orientation with respect to the local temperature gradient is superior to that of the base material. The current hypothesis is that nucleation at the melt-pool border happens due to remelting microsegregations from former solidification processes leading to constitutional undercooling directly at the onset of solidification. This study offers the opportunity to understand and exploit this mechanism for different manufacturing processes. MDPI 2020-12-03 /pmc/articles/PMC7731160/ /pubmed/33287217 http://dx.doi.org/10.3390/ma13235517 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 Rausch, Alexander M. Gotterbarm, Martin R. Pistor, Julian Markl, Matthias Körner, Carolin New Grain Formation by Constitutional Undercooling Due to Remelting of Segregated Microstructures during Powder Bed Fusion |
title | New Grain Formation by Constitutional Undercooling Due to Remelting of Segregated Microstructures during Powder Bed Fusion |
title_full | New Grain Formation by Constitutional Undercooling Due to Remelting of Segregated Microstructures during Powder Bed Fusion |
title_fullStr | New Grain Formation by Constitutional Undercooling Due to Remelting of Segregated Microstructures during Powder Bed Fusion |
title_full_unstemmed | New Grain Formation by Constitutional Undercooling Due to Remelting of Segregated Microstructures during Powder Bed Fusion |
title_short | New Grain Formation by Constitutional Undercooling Due to Remelting of Segregated Microstructures during Powder Bed Fusion |
title_sort | new grain formation by constitutional undercooling due to remelting of segregated microstructures during powder bed fusion |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7731160/ https://www.ncbi.nlm.nih.gov/pubmed/33287217 http://dx.doi.org/10.3390/ma13235517 |
work_keys_str_mv | AT rauschalexanderm newgrainformationbyconstitutionalundercoolingduetoremeltingofsegregatedmicrostructuresduringpowderbedfusion AT gotterbarmmartinr newgrainformationbyconstitutionalundercoolingduetoremeltingofsegregatedmicrostructuresduringpowderbedfusion AT pistorjulian newgrainformationbyconstitutionalundercoolingduetoremeltingofsegregatedmicrostructuresduringpowderbedfusion AT marklmatthias newgrainformationbyconstitutionalundercoolingduetoremeltingofsegregatedmicrostructuresduringpowderbedfusion AT kornercarolin newgrainformationbyconstitutionalundercoolingduetoremeltingofsegregatedmicrostructuresduringpowderbedfusion |