The nucleation of Fe-Rich phases on oxide films in Al-11.5Si-0.4Mg cast alloys

Cao, X.; Campbell, John B.

doi:10.1007/s11661-003-0253-3

Cited by 198 publications

(128 citation statements)

References 10 publications

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“…However, a simple description of the interfacial energy is not possible [17,43]. In general, nucleating potency can be assessed by comparisons of the perfectness of the lattice matching at the solid/substrate interface during heterogeneous nucleation, and the better the lattice matching, the higher the nucleation potency.…”

Section: The Potency Of Mgal 2 O 4 As Nucleation Substratementioning

confidence: 99%

“…Their results showed that in dilute Alalloys containing less than 1.5wt.%(Si+Fe) (all compositions given hereafter in wt.%), nucleation of the α-Al phase could be promoted by the addition of oxide particles although the grain size evolution associated with the oxide addition was not reported. Cao and Campbell [17] investigated the formation of Fe-bearing intermetallics on oxides in Al-Si cast alloys. Their results indicated that the wetted side of an oxide film can act as nucleation sites for the Fe-bearing intermetallics.…”

Section: Introductionmentioning

confidence: 99%

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Mechanisms of enhanced heterogeneous nucleation during solidification in binary Al–Mg alloys

Li¹,

Wang²,

Fan³

2012

Acta Materialia

183

120

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This paper investigates the mechanisms involved in the grain refinement of Al-Mg alloys through varying the Mg content and applying intensive melt shearing. It was found that the oxide formed in Al-Mg alloys under normal melting conditions is MgAl 2 O 4 , which displays an equiaxed and faceted morphology with {111} planes exposed as its natural surfaces. Depending on the Mg content, MgAl 2 O 4 particles exist either as oxide films in dilute Al-Mg alloys (Mg<1wt.%) or naturally dispersed discrete particles in more concentrated Al-Mg alloys (Mg>1wt.%). Such MgAl 2 O 4 particles can act as potent sites for nucleation of α-Al grains, which is evidenced by the well-defined cube-on-cube orientation relationship between MgAl 2 O 4 and α-Al. Enhanced heterogeneous nucleation in Al-Mg alloys can be attributed to the high potency of MgAl 2 O 4 particles with a lattice misfit of 1.4% and the increased number density of MgAl 2 O 4 particles due to either natural dispersion by the increased Mg content or forced dispersion through intensive melt shearing. It was also found that intensive melt shearing leads to significant grain refinement of dilute Al-Mg alloys by effective dispersion of the MgAl 2 O 4 particles entrapped in oxide films, but it has marginal effect on the grain refinement of concentrated Al-Mg alloys, where MgAl 2 O 4 particles have been naturally dispersed into individual particles by the increased Mg content.

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Section: The Potency Of Mgal 2 O 4 As Nucleation Substratementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mechanisms of enhanced heterogeneous nucleation during solidification in binary Al–Mg alloys

Li¹,

Wang²,

Fan³

2012

Acta Materialia

183

120

View full text Add to dashboard Cite

show abstract

“…[42,43] The outer interfaces of oxide films appear to act as preferred substrates for the nucleation and growth of some Ferich phases, especially b phases along oxide films. [4,44] Good atomic contact is expected between the wetted side of the oxide film and Fe-rich phases or aluminum matrix.…”

Section: D Morphology Of Fe-rich Phasesmentioning

confidence: 99%

Interplay Between Melt Flow and the 3D Distribution and Morphology of Fe-Rich Phases in AlSi Alloys

Mikołajczak

Ratke

2014

Metall Mater Trans A

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The presence of Fe aids in establishing the mechanical and physical properties of AlSi alloys and is also one of the main impurities leading to formation of b-Al 5 FeSi intermetallics. This study aims to understand the effect of fluid flow on the dendritic microstructure with intermetallics in Al-5/7/9 wt pct Si-0.2/0.5/1.0 wt pct Fe alloys that are directionally solidified under defined thermal and fluid flow conditions. We made extensive use of 3D X-ray tomography to obtain a better insight into the morphology and formation of the intermetallics. Three-dimensional (3-D) distribution of intermetallics presented here shows that the growth of large b-Al 5 FeSi due to forced flow occurs in the eutectic specimen center and together with an increase in the number density of b precipitates. The 3D reconstructions have verified the b shaped to be curved, bent with twining, branched, and to have imprints, holes, and propeller-shaped platelets. The 3D views showed that hole-shaped b arose from the lateral growth around a-Al dendrites. These views also confirmed the phenomenon of shortening of b as an effect of flow in the dendritic region, where b could be fragmented or completely remelted, and ultimately resulting in microstructures with shorter b-Al 5 FeSi and increases in number density. The analysis revealed an interaction between melt flow, 3D distribution, and the morphology of b-Al 5 FeSi. The growth of a large and complex group of b intermetallics can reduce the melt flow between dendrites and strengthen pore nucleation and eutectic colonies nucleation, leading to lower permeability of the mushy zone and increased porosity in the castings.

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“…The effect of oxide inclusions on the nucleation of iron bearing intermetallic phases in aluminum alloys is well documented. [34][35][36] Based on lattice matching, Cao and Campbell [34] proposed that MgO, MgAl 2 O 4 , a-Al 2 O 3 , and c-Al 2 O 3 are all potent substrates for the nucleation of a Fe intermetallic particles. The intermetallic nucleation mechanism can be either by direct nucleation on the dispersed oxides or by multistep nucleation, where an intermediate compound first forms on the oxide particles, which then nucleate the iron-based intermetallics.…”

Section: Fe Bearing Intermetallic Phasementioning

confidence: 99%

Influence of Intensive Melt Shearing on the Microstructure and Mechanical Properties of an Al-Mg Alloy with High Added Impurity Content

Kumar

Babu

Scamans

et al. 2011

Metall Mater Trans A

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We have investigated the influence of melt conditioning by intensive shearing on the mechanical behavior and microstructure of Al-Mg-Mn-Fe-Cu-Si alloy sheet produced from a small book mold ingot with high added impurity content. The melt conditioned ingot has fine grains throughout its cross section, whereas a conventionally cast ingot, without melt shearing, has coarser grains and shows a wider variation of grain size. Both needle-shaped and coarse Chinese script iron bearing intermetallic particles are found in the microstructure at the center of the conventionally processed ingot, but for the melt conditioned ingot, only fine Chinese script intermetallic particles are observed. In addition to the iron bearing intermetallics, Mg 2 Si particles are also observed. The ingots were rolled to thin sheet and solution heat treated (SHT). During rolling, the iron-based intermetallics and Mg 2 Si particles are broken and aligned along the rolling direction. Yield strength (YS), ultimate tensile strength (UTS), and elongation of the intensively melt sheared and processed sheet are all improved compared to the conventionally cast and processed sheet. Fractographic analysis of the tensile fracture surfaces shows that the clustered and coarse iron bearing intermetallic particles are responsible for the observed reduction in mechanical properties of the conventionally cast sheet. We have shown that by refining the initial microstructure of the ingot by intensive shear melt conditioning, it is possible to achieve improved mechanical properties at the final sheet gage of an AlMgMn alloy with a high content of impurities.

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The nucleation of Fe-Rich phases on oxide films in Al-11.5Si-0.4Mg cast alloys

Cited by 198 publications

References 10 publications

Mechanisms of enhanced heterogeneous nucleation during solidification in binary Al–Mg alloys

Mechanisms of enhanced heterogeneous nucleation during solidification in binary Al–Mg alloys

Interplay Between Melt Flow and the 3D Distribution and Morphology of Fe-Rich Phases in AlSi Alloys

Influence of Intensive Melt Shearing on the Microstructure and Mechanical Properties of an Al-Mg Alloy with High Added Impurity Content

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