Effects of cover gases on melt protection of Mg alloys

Ha, Wansoo; Kim, Young‐Jig

doi:10.1016/j.jallcom.2005.12.003

Cited by 73 publications

(32 citation statements)

References 6 publications

(5 reference statements)

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“…(1). Equation (2) shows the reverse reaction against oxidation of Ca. Gibbs free energy values (ÁG f ) of the equations exhibited À492:858 and +531.087 kJ/mol, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…If gas concentration increases during melting, it has also bad influence on corrosion resistance of steel based equipments. 2) In order to reduce the use of melt protective gases, many researchers have performed studies to improve the flame resistance of Mg alloys through alloying. It is well known that Ca are used to improve the flame and oxidation resistance of Mg alloys.…”

Section: Introductionmentioning

confidence: 99%

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Effect of CaO on Oxidation Resistance and Microstructure of Pure Mg

Lee

Kim

2008

Mater. Trans.

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This study was carried out to examine reduction mechanism of CaO and to investigate behaviors of CaO in pure Mg in terms of microstructure, oxidation resistance and phase formation. Pure Mg was used instead of Mg alloys to minimize the effects of other elements. With respect to CaO content, microstructures of the alloys showed prominent grain refinement. Mg 2 Ca phase was formed even in 0.07CaO added pure Mg by reduction, while Mg 2 Ca phase was formed over 1.35Ca added pure Mg. With respect to CaO content, the hardness of CaO added pure Mg was increased by grain refinement. From oxidation test by TGA, the oxidation behavior of CaO added Mg was similar to that of Ca added Mg. From AES result, there was the thin oxide layer mixed with MgO and CaO in CaO added Mg.

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“…(1). Equation (2) shows the reverse reaction against oxidation of Ca. Gibbs free energy values (ÁG f ) of the equations exhibited À492:858 and +531.087 kJ/mol, respectively.…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of CaO on Oxidation Resistance and Microstructure of Pure Mg

Lee

Kim

2008

Mater. Trans.

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“…Such MgAl 2 O 4 particles were formed from MgO as a result of the initial oxidation. The Pilling-Bedworth ratio (PBR) is the ratio of oxide volume produced over the metal volume consumed [32][33][34]. Usually, an oxidising system with PBR>1 will form a continuous oxide film, while systems with PBR<1 will produce discrete particles.…”

Section: Formation Of Oxide In Al-mg Alloysmentioning

confidence: 99%

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

Li¹,

Wang²,

Fan³

2012

Acta Materialia

177

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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“…Since SF 6 has been identified as a GHG [5,7,8], the protective films formed on molten magnesium and its alloys under gas protection have been an active subject of research, with the aim of finding suitable industrial alternatives to SF 6 gas for melt protection [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. The use of SF 6 gas will be banned from the European Union from 2018 [22] (as cited in Reference [23]), in which case, replacement of SF 6 as a cover gas in the Mg industry would no longer be eligible as Clean Development Mechanism (CDM) project or Joint Implementation (JI) project, nor sell the reduced emission as 'carbon credits' [24].…”

Section: Introductionmentioning

confidence: 99%

Melt Protection of Mg-Al Based Alloys

Balart

Patel

Fan

2016

Metals

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This paper reports the current status of Mg melt protection in view to identify near-future challenges, but also opportunities, for Mg melt protection of Mg-Al based alloys. The goal is to design and manufacture sustainable Mg alloys for resource efficiency, recycling and minimising waste. Among alternative cover gas technologies for Mg melt protection other than SF 6 : commercially available technologies containing-HFC-134a, fluorinated ketone and dilute SO 2 -and developed technologies containing solid CO 2 , BF 3 and SO 2 F 2 , can potentially produce toxic and/or corrosive by-products. On the other hand, additions of alkaline earth metal oxides to Mg and its alloys have developed a strong comparative advantage in the field of Mg melt protection. The near-future challenges and opportunities for Mg-Al based alloys include optimising and using CO 2 gas as feedstock for both melt protection and grain refinement and TiO 2 additions for melt protection.

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Effects of cover gases on melt protection of Mg alloys

Cited by 73 publications

References 6 publications

Effect of CaO on Oxidation Resistance and Microstructure of Pure Mg

Effect of CaO on Oxidation Resistance and Microstructure of Pure Mg

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

Melt Protection of Mg-Al Based Alloys

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