Microstructural Evolution in AlMgSi Alloys during Solidification under Electromagnetic Stirring
Equiaxed solidification of AlMgSi alloys with Fe and Mn was studied by electromagnetic stirring to understand the effect of forced flow. The specimens solidified with a low cooling rate, low temperature gradient, and forced convection. Stirring induced by a coil system around the specimens caused a...
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doaj-2ebb30e073ae43b3b557762f35c8c9da2020-11-24T23:25:29ZengMDPI AGMetals2075-47012017-03-01738910.3390/met7030089met7030089Microstructural Evolution in AlMgSi Alloys during Solidification under Electromagnetic StirringPiotr Mikolajczak0Institute of Materials Technology, Poznan University of Technology, Piotrowo 3, 60-965 Poznan, PolandEquiaxed solidification of AlMgSi alloys with Fe and Mn was studied by electromagnetic stirring to understand the effect of forced flow. The specimens solidified with a low cooling rate, low temperature gradient, and forced convection. Stirring induced by a coil system around the specimens caused a transformation from equiaxed dendritic to rosette morphology with minor dendrites and, occasionally, spheroids. This evolution was quantitatively observed with specific surface Sv. The precipitation sequence of the phases was calculated using the CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) technique. Melt flow decreased secondary dendrite arm spacing λ2 in the AlSi5Fe1.0 alloy, while λ2 increased slightly in Mg-containing alloys. The length of detrimental β-Al5FeSi phases decreased only in AlSi5Fe1.0 alloy under stirring, whereas in Mg-containing alloys, changes to the β-Al5FeSi phase were negligible; however, in all specimens, the number density increased. The modification of Mn-rich phases, spacing of eutectics, and Mg2Si phases was analyzed. It was found that the occurrence of Mg2Si phase regions reduced fluid flow in the late stages of solidification and, consequentially, reduced shortening of β-Al5FeSi, diminished secondary arm-ripening caused by forced convection, and supported diffusive ripening. However, the Mg2Si phase was found to have not disturbed stirring in the early stage of solidification, and transformation from dendrites to rosettes was unaffected.http://www.mdpi.com/2075-4701/7/3/89aluminum alloyselectromagnetic stirringdendrite arm spacingrosettesMg2Si phasessolidification |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Piotr Mikolajczak |
spellingShingle |
Piotr Mikolajczak Microstructural Evolution in AlMgSi Alloys during Solidification under Electromagnetic Stirring Metals aluminum alloys electromagnetic stirring dendrite arm spacing rosettes Mg2Si phases solidification |
author_facet |
Piotr Mikolajczak |
author_sort |
Piotr Mikolajczak |
title |
Microstructural Evolution in AlMgSi Alloys during Solidification under Electromagnetic Stirring |
title_short |
Microstructural Evolution in AlMgSi Alloys during Solidification under Electromagnetic Stirring |
title_full |
Microstructural Evolution in AlMgSi Alloys during Solidification under Electromagnetic Stirring |
title_fullStr |
Microstructural Evolution in AlMgSi Alloys during Solidification under Electromagnetic Stirring |
title_full_unstemmed |
Microstructural Evolution in AlMgSi Alloys during Solidification under Electromagnetic Stirring |
title_sort |
microstructural evolution in almgsi alloys during solidification under electromagnetic stirring |
publisher |
MDPI AG |
series |
Metals |
issn |
2075-4701 |
publishDate |
2017-03-01 |
description |
Equiaxed solidification of AlMgSi alloys with Fe and Mn was studied by electromagnetic stirring to understand the effect of forced flow. The specimens solidified with a low cooling rate, low temperature gradient, and forced convection. Stirring induced by a coil system around the specimens caused a transformation from equiaxed dendritic to rosette morphology with minor dendrites and, occasionally, spheroids. This evolution was quantitatively observed with specific surface Sv. The precipitation sequence of the phases was calculated using the CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) technique. Melt flow decreased secondary dendrite arm spacing λ2 in the AlSi5Fe1.0 alloy, while λ2 increased slightly in Mg-containing alloys. The length of detrimental β-Al5FeSi phases decreased only in AlSi5Fe1.0 alloy under stirring, whereas in Mg-containing alloys, changes to the β-Al5FeSi phase were negligible; however, in all specimens, the number density increased. The modification of Mn-rich phases, spacing of eutectics, and Mg2Si phases was analyzed. It was found that the occurrence of Mg2Si phase regions reduced fluid flow in the late stages of solidification and, consequentially, reduced shortening of β-Al5FeSi, diminished secondary arm-ripening caused by forced convection, and supported diffusive ripening. However, the Mg2Si phase was found to have not disturbed stirring in the early stage of solidification, and transformation from dendrites to rosettes was unaffected. |
topic |
aluminum alloys electromagnetic stirring dendrite arm spacing rosettes Mg2Si phases solidification |
url |
http://www.mdpi.com/2075-4701/7/3/89 |
work_keys_str_mv |
AT piotrmikolajczak microstructuralevolutioninalmgsialloysduringsolidificationunderelectromagneticstirring |
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1725557226055139328 |