High temperature oxidation of AZ91D magnesium alloy granule during in-situ melting

Jafari, Hassan; Idris, Mohd Hasbullah; Ourdjini, Ali

doi:10.1016/j.corsci.2010.10.012

Cited by 22 publications

(13 citation statements)

References 29 publications

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“…The authors proved and reported in their previous articles [20,21] that AZ91D granules were melted successfully during heating in air. However, formation and thickening of magnesium oxide on the surface of the granules during heating process encapsulated the melted granules and inhibited them from merging to form a pool of molten metal.…”

Section: Resultssupporting

confidence: 63%

Influence of Flux on Melting Characteristics and Surface Quality of In-Situ Melting AZ91D

Jafari

Idris

Ourdjini

et al. 2013

Materials and Manufacturing Processes

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In this article, the effect of flux on melting behavior and surface properties of investment casting of AZ91D magnesium alloy using in-situ melting technique was investigated. AZ91D granules together with different flux percentages and applications were charged into shell investment molds and heated at 750 C in argon-protected environment in order to produce AZ91D investment casting. Surface of castings and the occurred mold-metal interfacial reaction were analyzed. It was found that the application of flux together with the granules is essential to produce a solid investment cast alloy. The results showed that the use of flux mixed with the granules and sprinkled on the top of the granules as a layer produced higher surface quality casting. Microscopic examinations revealed that flux developed a barrier layer which reduced mold-metal reaction and contributed to an improved approach in AZ91D magnesium alloys investment casting process.

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Section: Resultssupporting

confidence: 63%

Influence of Flux on Melting Characteristics and Surface Quality of In-Situ Melting AZ91D

Jafari

Idris

Ourdjini

et al. 2013

Materials and Manufacturing Processes

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“…Figure 4a shows two regions, including slightly oxidized granules (gray) on the top and relatively oxidized granules (dark gray) at the bottom of the mold. The previous results reported by the authors [16] showed that grayish and dark grayish colors in the heated granules did not refer to any severe oxidation. However, increasing heating temperature to 750°C and 800°C caused two additional regions of white and light green colors to emerge below the top region (Figures 4c and d).…”

Section: Figures 3a -D Show the Top View Of Heated Granules Inmentioning

confidence: 52%

“…Figure 2 shows a top view of the two molds containing granules and oxidation residues after heating at 750°C for 30 min. As can be seen from Figure 2a, in the mold charged with mixed granule and flux, a considerable amount of magnesium oxide [16] formed on the top of the granules. This is the result of heating the granules in an unprotected environment, causing severe oxidation and ignition.…”

Section: Methodsmentioning

confidence: 99%

Characterization of AZ91D Granules Covered with a Flux during In‐Situ Melting

Jafari

Idris

Ourdjini

et al. 2012

Part & Part Syst Charact

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Oxidation and melting behaviors of AZ91D granules throughout the in-situ melting process using flux were investigated. The granules were heated under unprotected environment at four different temperatures between 650 and 800°C, for the durations of 30 and 60 min. The products of heating process were characterized macroscopically and the oxides formed on the granules were examined using field emission scanning electron microscope, energy dispersive X-ray spectroscopy and X-ray diffraction analysis. Thermal analysis was used to reveal the response of the granules to heating during the in-situ melting. The results showed that the granules experienced severe oxidation even in the presence of the flux, and significant amount of them changed to a powdered state due to oxidation and combustion, especially at 800°C. It was discovered that the granules melted during heating; however, oxides formed on their surface encapsulated the molten metal and prevented the liquids from merging. The results also revealed that increasing heating temperature and time enhanced mold-magnesium reaction resulted in the entrance of mold materials into the oxidation residues.

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“…Before heating the furnace, the crucible was totally covered with a steel plate (not sealed) for the purpose of lowering the oxygen content inside the enclosed area during melting 18 and, therefore, prevent catastrophic oxidation, ignition and burning of Mg metal. 19 This protecting procedure has been used previously during the melting of pure Mg, 11 Mg-1?5Ca (in wt-%) 11 and AZ91D alloys. 13 During heating the furnace and melting, a 95%N 2 gas flow from a nitrogen generator unit was maintained in the furnace chamber through a pipe connection into the top of the furnace chamber.…”

Section: Protecting Melt From Oxidationmentioning

confidence: 99%

Surface oxidation of molten AZ31, AM60B and AJ62 magnesium alloys in air

Balart

Fan

2014

International Journal of Cast Metals Research

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The surface of stagnant Mg-Al based alloy melts has been exposed to air: AZ31 alloy, at 640uC for 10 min and at 650uC for 10 s; AM60B alloy at 650uC for 10 s and AJ62 alloy at 690uC for 10 s. After oxidising, the samples were sand quenched. The macroscopic morphology of the surfaces exhibited regions of non-nodular growth (in a layer manner) and regions of nodular growth. The microscopic morphology of the surfaces and the nature of the surface reaction products have been analysed using field emission gun (FEG)-SEM and X-ray diffraction (XRD) techniques, respectively. FEG-SEM results revealed that all these morphologies, namely, sponge-like, nodular and layer, were porous and, therefore, were non-protective with respect to evaporation and oxidation of Mg, Zn and Sr. XRD results indicated that in all these regions, MgO was the main oxidation product along with traces of AlN. Additionally, traces of ZnO were found in the nonnodular and nodular regions of AZ31 alloy containing 1?16 wt-%Zn for both oxidation conditions and, in the nodular region of AM60B alloy containing 0?05 wt-%Zn, relative to a more vigorous reaction condition. This trace ZnO content reflected the Zn levels of the three magnesium alloys investigated and the oxidation conditions. Traces of SrO were found in the nodular region of AJ62 alloy containing 2?5 wt-%Sr, relative to a more vigorous reaction condition.

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High temperature oxidation of AZ91D magnesium alloy granule during in-situ melting

Cited by 22 publications

References 29 publications

Influence of Flux on Melting Characteristics and Surface Quality of In-Situ Melting AZ91D

Influence of Flux on Melting Characteristics and Surface Quality of In-Situ Melting AZ91D

Characterization of AZ91D Granules Covered with a Flux during In‐Situ Melting

Surface oxidation of molten AZ31, AM60B and AJ62 magnesium alloys in air

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