The effects of some elements on the igniting temperature of magnesium alloys

Zhao, Weimin; Sun, Yihan; Li, Haipeng; Liang, Chunyong

doi:10.1016/j.mseb.2005.09.064

Cited by 30 publications

(8 citation statements)

References 4 publications

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“…[8] The effect of Be on the oxidation resistance of Mg is well known. [2,[8][9][10][11] The addition of ppm levels of Be to Mg casting alloys has played a major role in the widening use of Mg in automotive cast parts. Be is surface active in Mg, [2,9,11] i.e., segregates to the surface thereby decreasing the surface energy of Mg. Be was found to enrich on the outermost layer of molten magnesium and form a dense BeO layer that prevents oxygen transport through the scale.…”

Section: Introductionmentioning

confidence: 99%

“…[2,[8][9][10][11] The addition of ppm levels of Be to Mg casting alloys has played a major role in the widening use of Mg in automotive cast parts. Be is surface active in Mg, [2,9,11] i.e., segregates to the surface thereby decreasing the surface energy of Mg. Be was found to enrich on the outermost layer of molten magnesium and form a dense BeO layer that prevents oxygen transport through the scale. [2] Czerwinski [2] reported that the non-protective scale formation on the AZ91 alloy is delayed when the Be addition is increased from 5 to 10 ppm at 487-547°C.…”

Section: Introductionmentioning

confidence: 99%

“…[2] Czerwinski [2] reported that the non-protective scale formation on the AZ91 alloy is delayed when the Be addition is increased from 5 to 10 ppm at 487-547°C. [11] Studies have also shown that rare earth (RE)-containing Mg alloys have improved oxidation resistance [5][6][7] RE elements are seen to diffuse outwards and undergo selective oxidation due to a high affinity to oxygen. [11] Studies have also shown that rare earth (RE)-containing Mg alloys have improved oxidation resistance [5][6][7] RE elements are seen to diffuse outwards and undergo selective oxidation due to a high affinity to oxygen.…”

Section: Introductionmentioning

confidence: 99%

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High Temperature Oxidation Behavior of Hypoeutectic Mg–Sr Binary Alloys: The Role of the Two‐Phase Microstructure and the Surface Activity of Sr

2014

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The high temperature oxidation behavior of Mg-Sr hypoeutectic alloys was investigated. The oxide layer was characterized after isothermal heating experiments that were conducted at 500°C in dry airflow for 12 h. It was seen that a non-uniform oxide scale formed on hypoeutectic Mg-Sr alloys with a two-phase structure whereby the oxide over the interdendritic intermetallic phase had a finer grain size than the oxide over the a-Mg dendrites. The interrupted tests on selected alloys showed that the two phases exhibit different oxidation sequences of Sr and Mg. It was observed that the intermetallic phase oxidizes first with the formation of both MgO and SrO on the surface. The oxidation proceeds with SrO and MgO formation on the a-Mg. This sequence is different from what is predicted as possible via thermodynamic calculations based on the activities of the elements on the two-phases. SEM/EDS analyses revealed that the Sr surface-enrichment has occurred, which explains the differences between the observation and the assessment. Thermodynamic re-assessment suggested that the Sr enrichment on the surface due to the surface activity of Sr in Mg could largely determine the initial oxidation sequence.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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High Temperature Oxidation Behavior of Hypoeutectic Mg–Sr Binary Alloys: The Role of the Two‐Phase Microstructure and the Surface Activity of Sr

2014

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“…In contrast, adequate amount of covering flux (1.5 wt.%), provided good protection and no considerable oxidation and ignition were observed on the top of the melted granules. Even with direct exposure to oxygen during cooling (without using a lid) the casting was not affected because of the formation of a flux-magnesium product barrier on the surface of molten metal which is believed to be MgCl 2 Á MgO, as reported by Weimin et al [26].…”

Section: Resultsmentioning

confidence: 69%

“…The spectra illustrate that the layer close to the casting is dominated with magnesium oxide, whereas it contains a considerable amount of chloride and magnesium oxide close to the surface. The presence of chlorine element in the spectrum indicates that the flux combined with MgO [26] and prevented magnesium from severe reaction with oxygen from the surrounding air or mold. Detection of Al in EDS analysis of point A suggests that MgAl 2 O 4 is part of the severe oxidation products [28,30].…”

Section: Resultsmentioning

confidence: 99%

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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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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The effects of some elements on the igniting temperature of magnesium alloys

Cited by 30 publications

References 4 publications

High Temperature Oxidation Behavior of Hypoeutectic Mg–Sr Binary Alloys: The Role of the Two‐Phase Microstructure and the Surface Activity of Sr

High Temperature Oxidation Behavior of Hypoeutectic Mg–Sr Binary Alloys: The Role of the Two‐Phase Microstructure and the Surface Activity of Sr

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

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