Intermetallic Phases and Microstructure in AlSi Alloys Influenced by Fluid Flow

Mikołajczak, Piotr; Ratke, Lorenz

doi:10.1002/9781118062173.ch104

Cited by 8 publications

(8 citation statements)

References 19 publications

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“…In directional solidification of AlSi5/7/9Fe0.2/0.5/1.0 alloys [35], the eutectic spacing did not show any clear correlation with fluid flow, which was in agreement with earlier results by Sous [36].…”

Section: Eutecticssupporting

confidence: 82%

Microstructural Evolution in AlMgSi Alloys during Solidification under Electromagnetic Stirring

Mikołajczak

2017

Metals

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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 S v . 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 λ 2 in the AlSi5Fe1.0 alloy, while λ 2 increased slightly in Mg-containing alloys. The length of detrimental β-Al 5 FeSi phases decreased only in AlSi5Fe1.0 alloy under stirring, whereas in Mg-containing alloys, changes to the β-Al 5 FeSi phase were negligible; however, in all specimens, the number density increased. The modification of Mn-rich phases, spacing of eutectics, and Mg 2 Si phases was analyzed. It was found that the occurrence of Mg 2 Si phase regions reduced fluid flow in the late stages of solidification and, consequentially, reduced shortening of β-Al 5 FeSi, diminished secondary arm-ripening caused by forced convection, and supported diffusive ripening. However, the Mg 2 Si phase was found to have not disturbed stirring in the early stage of solidification, and transformation from dendrites to rosettes was unaffected.

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Section: Eutecticssupporting

confidence: 82%

Microstructural Evolution in AlMgSi Alloys during Solidification under Electromagnetic Stirring

Mikołajczak

2017

Metals

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“…In the directional solidification of the AlSi7Mg0.6 alloy [44], forced convection reduced λ E with increasing solidification velocity according to the well-known Jackson and Hunt relationship (4) and also increased eutectic spacing, e.g., for the solidification velocity of 90 µm/s from 3 to 7 µm. In accordance with earlier results obtained by Sous [56], directional solidification of AlSi5/7/9Fe0.2/0.5/1.0 alloys [57] did not present any clear coincidence of the eutectic spacing with melt flow.…”

Section: Eutecticssupporting

confidence: 92%

“…In this paper, the author studied precipitations, such as dendritic α-Al, AlSieutectic, Al 2 Cu, needle or platelet shaped β-Al 9 Fe 2 Si 2 and β-Al 8 Fe 2 Si, and complex manganese Al 15 Si 2 Mn 4 phases; these are all well known from many investigations (e.g., in [1][2][3][4][5][6]24,25,[57][58][59][60][61][62][63]) concerning aluminum alloy phases. In order to determine the sequence of precipitation of phases, property diagrams, Scheil solidification, and the ternary phase diagram were calculated for selected and examined alloys using the Thermo-Calc Software [26], which is widely used by materials scientists and engineers to generate material property data and gain insight into materials.…”

Section: Methodsmentioning

confidence: 99%

Effect of Rotating Magnetic Field on Microstructure in AlCuSi Alloys

Mikołajczak

2021

Metals

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The solidification of AlCuSi alloys with Mn and Fe was studied by rotating a magnetic field to understand the effect of melt flow. The specimens solidified with a forced convection, low cooling rate and low temperature gradient. Electromagnetic stirring generated by an electric coil around the specimens caused a transformation from equiaxed dendritic to rosette morphology, occasionally with spheroids and minor dendrites. The transformation was quantitatively observed with a specific surface Sv, that decreased for almost all alloys and marked the flow effect on α-Al. The computer coupling of phase diagrams and thermochemistry (CALPHAD) technique was applied for the calculation of phase diagrams and property diagrams. Forced convection decreased secondary dendrite arm spacing λ2 in almost all alloys, while it increased slightly in one studied alloy. The length of detrimental β-Al5FeSi phases decreased in the alloy, where β starts to precipitate in the presence of α-Al, while increasing in alloys where β starts as first and grows in the fully liquid melt. The average overall dimension of the Mn-rich phases increased in almost all alloys, and the number density decreased under flow. The modification of spacing for AlSi-eutectics and Al2Cu was analyzed. It was found that the occurrence of Al2Cu does not influence the fluid flow and vice versa.

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“…Similar Chinese script precipitates were also reported by Mikolajczak and Ratke [21] on an Al-7Si-1Fe alloy. However, this observation would not comply with the solidification path calculated for these alloys, [20] if it were assumed this morphology was associated with the hexagonal a h -Al 8 Fe 2 Si phase.…”

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confidence: 68%