The research on the effect of MgCO<sub>3 </sub>on the grain refinement in AZ31 magnesium alloy

Gao, Shiyou; Cui, Jie; Li, Q.‐C.; Zhang, Z.‐Q.

doi:10.1002/mawe.201000591

Cited by 9 publications

(8 citation statements)

References 9 publications

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“…The possible resultant products in the Mg-8Al alloy upon the addition of CO 2 gas at 740°C are Al 4 C 3 , MgO and Al 2 O 3 because the Gibbs free energy values of MgC 2 and Mg 2 C 3 , which are formed via the reaction of Mg with the newly generated C at 740°C, are positive [17]. The Gibbs free energy values for Al 4 C 3 , MgO and Al 2 O 3 , which are formed by the following reactions (1)–(3), are negative.…”

Section: Resultsmentioning

confidence: 99%

Effect of gaseous carbon dioxide on grain refinement in Mg-8Al alloy

Liu

You

Gao

et al. 2017

Materials Science and Technology

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A Mg-Al alloy was treated with gaseous carbon dioxide (CO2) and a refining process, and the grain refinement at each stage was investigated. The results indicated that CO2 and the subsequent refining process affect the grain refinement in the Mg-Al alloy. Moreover, the average grain size decreased from 254 to 89 µm, and the microhardness increased from 59.7 to 66.0 HV upon the addition of 9 litres of CO2. Increasing the time of the subsequent refining process to 30 min further decreased the grain size and increased the microhardness. Based on scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffraction analyses, the observed Al4C3 particles, which are attributed to the inoculation of CO2, are responsible for the grain refinement. This paper is part of a thematic issue on Light Alloys.

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Section: Resultsmentioning

confidence: 99%

Effect of gaseous carbon dioxide on grain refinement in Mg-8Al alloy

Liu

You

Gao

et al. 2017

Materials Science and Technology

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“…The previous section determined that the use of a fine filter within the well combined with Ar bubbling was the most effective for increasing mechanical properties and will be referred to as "filter + Ar bubbling" hereafter. with C inoculation is often described to be Al 4 C 3 [2,5,9,17,18,26,87,89,92,95,107,121,135,136,138,140,[200][201][202]216,224,[230][231][232][233][234][235][236]242,244,249,250,253] but recent research point towards Al 2 MgC 2 [132,139,232,248,251]. The observations from Figure 5-14c show indications of the remnants of these phases by the presence of C and O around the blocky Al 8 Mn 5 as they are highly hydrophobic as described by Equation 17and observations in literature [132,139,248].…”

Section: In-situ Grain Refinement Using C 2 Clmentioning

confidence: 99%

“…None, not practical [4,15,18,89,90,92,93,136,196,205,207,208,214,[223][224][225][226][227][228][229] Carbon Based Grain Refiners (C, Al-C, Mg-Al-C, SiC, etc. )…”

Section: Carbides or Duplex Particlesmentioning

confidence: 99%

“…Too much bubbling of CO or CO 2 reduced mechanical properties by an unknown mechanism and bubbling Ar, He, H 2 , HCl, N, O 2 and dried air gave no significant refinement [196]. The bubbling of CO 2 into Mg is proposed to follow Equation 21 [136] [136,207,225,226] or MgCO 2 -other C source mixtures [227] have been used with success by many researchers. The addition of MgCO 3 releases CO 2 according to Equation 22 [227] and was just as effective as superheating and CO bubbling [207].…”

Section: Carbonaceous Gases and Carbonatesmentioning

confidence: 99%

“…The alternative carbonate MnCO 3 [93,228] also showed refinement. The refinement mechanism using carbonates is usually attributed to Al 4 C 3 nucleating particles [136] or a duplex phase of Al 8 Mn 5 on Al 4 C 3 particles [93,227,228]. However, the formation of MgO within the melt may reduce mechanical properties.…”

Section: Carbonaceous Gases and Carbonatesmentioning

confidence: 99%

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Inclusion removal and grain refinement of magnesium alloy castings

Elsayed¹

2021

Preprint

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Magnesium alloys show promise to be materials for lightweighting of automotive and aerospace vehicles improving fuel efficiencies and vehicle performance. A majority of magnesium alloy components are produced using casting where susceptibility to forming inclusions and coarse grain sizes could result. Development of effective inclusion removal techniques and better understanding of grain refinement of magnesium alloys could help in improving their mechanical properties to advance them to more structurally demanding applications. This research aimed to develop an environmentally friendly alternative to the grain refinement and inclusion removal capabilities of carbon based hexachloroethane as it releases dioxins, chlorine gas and corrodes foundry equipment. A secondary aim was to pioneer in-situ neutron diffraction to examine the solidification of magnesium alloys. The research involved preparing tensile samples of AZ91E magnesium alloy using permanent mould casting. Inclusion removal was conducted by using filtration and argon gas bubbling. Castings grain refined using hexachloroethane (0.25, 0.50 and 0.75 wt.%) were compared against ex-situ aluminum-silicon carbide and in-situ aluminum-carbon based grain refiners combined with filtration and argon gas bubbling. Further, in-situ neutron diffraction was utilized for phase analysis and fraction solid determination of magnesium-zinc and magnesium-aluminum alloys. There was a significant improvement in yield strength, ultimate tensile strength and elongation with filtration plus argon bubbling, carbon inoculation or both filtration plus argon bubbling and carbon inoculation. The results indicated that the mechanism of the observed ~20% reduction in grain sizes with carbon inoculation (hexachloroethane, ex-situ aluminum-silicon carbide and in-situ aluminum-carbon) was explained through duplex nucleation of Mn-Al and Al-Mg-C-O (likely Al2MgC2) phases. Finally, in-situ neutron diffraction was used to follow the formation of Mg17Al12 eutectic phase in a magnesium-9 wt.% aluminum alloy. For the magnesium-zinc alloys, in-situ neutron diffraction enabled characterization of the effects of zirconium to the fraction solid growth of (1010), (0002) and (1011) α-Mg planes. The societal and environmental impact of this research is significant. There is a clear demonstration of alternatives to the universally used hexachloroethane grain refiner promoting harmful emissions. Improved mechanical properties resulting from new grain refinement and iv inclusion filtration are a major advancement in promoting weight reduction, improved castability and decreased environmental impact for automotive and aerospace industries.

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