Oxidation of aluminum-magnesium melts in air, oxygen, flue gas, and carbon dioxide

Cochran, C. Norman; Belitskus, David; Kinosz, D. L.

doi:10.1007/bf02657663

Cited by 91 publications

(47 citation statements)

References 3 publications

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“…It has been established theoretically and experimentally in the literature that the formation of oxides in Al-Mg alloys is dependent on the Mg content in the alloy and the melting conditions [25][26][27][28][29]. However, there is very limited information on the microstructural features of the oxides formed in liquid Al-Mg alloys due to the associated experimental difficulties [27].…”

Section: The Nature Of Oxides In Molten Al-mg Alloysmentioning

confidence: 99%

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

Li¹,

Wang²,

Fan³

2012

Acta Materialia

180

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 Nature Of Oxides In Molten Al-mg Alloysmentioning

confidence: 99%

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

Li¹,

Wang²,

Fan³

2012

Acta Materialia

180

120

View full text Add to dashboard Cite

show abstract

“…This layer from 3004 #2 was ~7-8 cm thick and was much more fragmented compared with the isolated, self-contained particles observed in the dross from alloy 3004 #1. A low magnification image showing the distribution of particles within the dross layer is shown in Fig 4.10 (compare with oxide particle morphology shown in Figure 4. [8][9][10] This is exactly the progression of microstructure/phase development observed in the dross from alloy 3004 #2. Clearly, even in a low-Mg alloy such as 3004, oxidation of the molten Al is controlled by the rate at which the Mg is oxidized and thus consumed.…”

Section: Alloy 3004 (Low Mg) -mentioning

confidence: 63%

“…It was ~1 cm in diameter/length and exhibited the characteristics typical of the Al metal encapsulation described for alloy 1350 (areas of trapped Al metal are denoted by arrows in Fig 4.8 results in extremely rapid oxidation rates and, thus, extensive dross formation for these alloys. This is termed breakaway oxidation [10] and it will continue at an accelerated rate until the Mg near the surface of the melt has been depleted. At that point, the much slower oxidation of the molten Al to form α-Al 2 O 3 begins.…”

Section: Alloy 3004 (Low Mg) -mentioning

confidence: 99%

“…Excessive stress is generated during the accelerated reaction between MgO and a-Al 2 O 3 and increased amounts of MgAl 2 O 4 form with increased holding time until the local Mg is depleted. [8][9][10] The stresses generated during these phase transformations in the melt will cause the oxide films to fracture and accelerated (breakaway) oxidation will continue as trapped Al is released. In the case of alloy 3004 #2, there was less trapped Al but increased oxide formed.…”

Section: Alloy 3004 (Low Mg) -mentioning

confidence: 99%

“…[1,2,4,6,7,9-11] Work of this type has usually been done on a proprietary basis by an individual company for a particular Al alloy and melt practice and, thus, results are generally not reported in the open literature. Most of the detailed characterization that has been reported has been conducted on relatively pure Al alloys melted in the laboratory [8][9][10] which, while providing valuable information with regard to dross growth mechanisms under controlled conditions, may not be representative of the more varied microstructural development associated with large-scale industrial furnaces.…”

Section: Introductionmentioning

confidence: 99%

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Reduction of Oxidative Melt Loss of Aluminum and Its Alloys

Das¹,

Ningileri²

2006

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Physical and Computational Models of Free Surface Related Defects in Low‐Pressure Die‐Cast Aluminum Alloy Wheels

et al. 2011

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The difference of die filling, which can be characterized by the free surface flow behavior, has a strong influence on the quality of casting components. In the case of cast aluminum alloy wheels, an undesired filling pattern with excessive turbulence can cause portions of the surface oxide film to be entrained within the bulk liquid resulting in defects such as cosmetic paint-pops, hot tears, porosity and rim-leaks.To investigate the influence of die filling on defect formation in low-pressure die-cast aluminum wheels, a water analogue physical model was built, instrumented and tested to simulate the free surface behavior during die filling of a low-pressure die-cast (LPDC) wheel. The physical model contains a transparent planar die section which was manufactured out of the geometry of a production die, and an automatic pressure control system that achieves liquid feeding conditions similar to the industrial process. A set of die filling tests with different venting conditions was carried out to explore the role of venting on the free surface behavior of water and to produce data for validation of a computational model. The computational model was developed, based on the commercial computational fluid dynamics code ANSYS CFX, for the purposes of predicting the flow conditions during die filling, providing qualitative a nd quantitative flow information that are otherwise not possible to obtain through experimental measurement, and identifying key features that influences the flow during die filling at a lower cost of time and labor.Comparison between the experimental and numerical data has shown that the computational model was able to qualitatively reproduce the flow behavior observed in the water model in the conditions tested. Both the experimental and the model results indicate that the entrainment of surface oxide films and air bubbles could occur at the outboard rim flange during the filling of the flange, below the free surface of the returning waves in the spoke and at the junction of the iii hub and the spoke during the filling of the hub. In both cases, venting conditions have been proved crucial and the importance of vent design in commercial die design was highlighted.iv

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Oxidation of aluminum-magnesium melts in air, oxygen, flue gas, and carbon dioxide

Cited by 91 publications

References 3 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

Reduction of Oxidative Melt Loss of Aluminum and Its Alloys

Physical and Computational Models of Free Surface Related Defects in Low‐Pressure Die‐Cast Aluminum Alloy Wheels

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