Characterisation of the surface films formed on molten magnesium in different protective atmospheres

Pettersen, Gunnar; Øvrelid, Eivind; Tranell, Gabriella; Fenstad, Jo; Gjestland, Haavard

doi:10.1016/s0921-5093(01)01750-6

Cited by 66 publications

(48 citation statements)

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“…Until now, researches on the reaction between magnesium and mold sand has been carried out to understand the mechanisms of sand mold protection by using cover gas on magnesium melts. [3][4][5] Therefore, the basic reaction between magnesium melt and mold sand has not been studied. This study examines the effect of mold material and pouring temperature on casting surface condition of the AZ91 alloy.…”

Section: Introductionmentioning

confidence: 99%

Casting Surface of AZ91 Alloy and Its Reaction with Sand Mold

et al. 2008

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Due to its light weight and abundance as a resource, the utilization of magnesium is increasing. AZ91 alloy is the most common cast magnesium alloy and is widely used as die-casting material. AZ91 is also used for sand mold casting. In sand mold casting, reaction with mold sand is expected because magnesium is a very reactive element. This study investigated the surface condition of AZ91 castings using sand mold.Higher pouring temperature promoted the reaction with silica sand, and the surface of castings became rough. Reacting with mold sand, Mg 2 Si and Mg and Al complex oxides were precipitated near the casting surface.

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Section: Introductionmentioning

confidence: 99%

Casting Surface of AZ91 Alloy and Its Reaction with Sand Mold

et al. 2008

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“…Because of this, a cover gas is required, and both SO 2 and SF 6 , mixed with N 2 , CO 2 , or dry air are the most common methods used to protect molten magnesium. Recently, the use of SF 6 has become more and more restricted, because of its expensive price and environmental issues. Studying the protective mechanism of SF 6 is very important for finding replacements.…”

Section: Introductionmentioning

confidence: 99%

“…Some investigations have been started, but the protective mechanism of SF 6 is still not very clear and requires further study. Couling [1,2] studied the protection of pure magnesium and the AZ91B alloy in atmospheres containing SF 6 . He found that SF 6 was consumed during the experiments and attributed this to the adsorption of SF 6 to an MgO surface or reaction to form MgF 2 .…”

Section: Introductionmentioning

confidence: 99%

Microstructure, Composition, and Depth Analysis of Surface Films Formed on Molten AZ91D Alloy under Protection of SF6 Mixtures

Xiong

Liu

2007

Metall Mater Trans A

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Molten magnesium and its alloy are easily oxidized during processing. SF 6 in conjunction with dilute gas is usually used to protect molten magnesium. The cover gas protects the melt by reacting with the metal to form a protective film on the melt surface. This article describes the investigation of the microstructure and composition of the surface film formed in a controlled atmosphere. The results showed that the film contained only MgO and MgF 2 . Both Auger electron spectroscopy (AES) depth profiling and scanning electron microscopy (SEM) observation indicated the film thickness to be in the range of 0.3 to 2 lm, and the composition of the film was uniform in depth. Particles containing magnesium fluoride formed on the interface between the oxide film and bulk magnesium, which corresponded to the concave areas from the surface observation by SEM. The results also showed that the film thickness increased with the increase of holding time and melting temperature. High concentration of SF 6 or high temperature will accelerate the reaction between magnesium and fluoride.

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“…The data of the diagram was calculated using the FactSage package (version 6.2). 14) In Table 3, the physical properties of magnesium and various magnesium compounds are presented. The values for ¦G ○ f are given for the formation of the compounds from standard states at 298 K. The values vary in different data collections, however the values presented here are taken from the identical data source.…”

Section: Mg ðLþ þ 1=2o 2 ðGþ ! Mgo ðSþmentioning

confidence: 99%

Protective Properties of SF<sub>6</sub> under Various Carrier Gases for the Protection of Molten Mg

et al. 2013

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Molten magnesium can oxidize rapidly in atmospheres containing oxygen. During the casting and handling of molten magnesium, it is essential to protect the melt from ignition. The protective gas normally contains air and/or CO 2 , and with a small amount of an inhibiting agent. This study examined the minimum amount of SF 6 gas needed depending on the type of carrier gas, as well as the effects of the melt temperature, exposure time and SF 6 concentration on the surface film of molten magnesium. The analysis methods of the surface film included the XPS/depth profile and SEM/EDS. The minimum amount of SF 6 gas concentration determined over a wide a range of different carrier gases, such as air, N 2 and CO 2 . The surface film thickness decreased with increasing SF 6 concentration under all conditions, such as the melt temperature, exposure time and different carrier gas.

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Characterisation of the surface films formed on molten magnesium in different protective atmospheres

Cited by 66 publications

References 1 publication

Casting Surface of AZ91 Alloy and Its Reaction with Sand Mold

Casting Surface of AZ91 Alloy and Its Reaction with Sand Mold

Microstructure, Composition, and Depth Analysis of Surface Films Formed on Molten AZ91D Alloy under Protection of SF6 Mixtures

Protective Properties of SF<sub>6</sub> under Various Carrier Gases for the Protection of Molten Mg

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