Effect of be addition on the oxidation behavior of Mg−Ca alloys at elevated temperature

Huang, Yan-Bin; Chung, In-Sang; You, Bong Sun; Park, Won-Wook; Choi, Byung Kwan

doi:10.1007/bf03027357

Cited by 38 publications

(14 citation statements)

References 8 publications

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Section: Discussion On Ignition Temperaturementioning

confidence: 99%

“…Because of the high P-B ratio of BeO (1.70) [62], the BeO film was considered a barrier to prevent oxygen penetration. Huang et al [165] reported an increase of 200 C in the ignition temperature of a Mg-2Ca alloy after alloying with 300 ppm (wt) Be. Zeng et al [166,167] reported that 0.3 wt.% Be-containing AZB910 could be melted without burning, even without a shielding gas.…”

Section: Bementioning

confidence: 99%

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Oxidation of magnesium alloys at elevated temperatures in air: A review

et al. 2016

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Highlights The oxidation behaviours of Mg alloys from low to high temperatures are reviewed. Characteristics of MgO during oxidation is discussed. Mechanisms of Mg oxidation is presented. Effect of various alloying elements is analysed. AbstractThis paper reviews (i) the oxidation of Mg alloys at elevated temperatures in air; (ii) the influence of alloying elements on the oxidation of Mg alloys; and (iii) the progress in the development of oxidation-resistant Mg alloys. Low oxidation rates have been shown by Mg alloys containing the alloying elements, Ca, Be and rare earth elements. However, these alloying elements may also decrease mechanical properties, such as ductility.

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Section: Discussion On Ignition Temperaturementioning

confidence: 99%

Section: Bementioning

confidence: 99%

Oxidation of magnesium alloys at elevated temperatures in air: A review

et al. 2016

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“…In the case of Be, even though the solute solubility of Be in Mg is almost zero [169], a Mg-0.15Be alloy exhibits an ignition temperature of 750 C [198]. Furthermore, microalloying of Mg-Ca alloy with Be produced a significantly higher ignition temperature of 1050 C [165] as shown in Table 2. Based on the analogy with Sr, the excellent ignition resistance by micro-alloying with Be may also be attributed to a surface active effect.…”

Section: Discussion On Ignition Temperaturementioning

confidence: 99%

“…Because of the high P-B ratio of BeO (1.70) [62], the BeO film was considered a barrier to prevent oxygen penetration. Huang et al [165] reported an increase of 200 C in the ignition temperature of a Mg-2Ca alloy after alloying with 300 ppm (wt) Be. Zeng et al [166,167] reported that 0.3 wt.% Becontaining AZB910 could be melted without burning, even without a shielding gas.…”

Section: Bementioning

confidence: 99%

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Influence of trace addition of Be on the oxidation behaviour of Mg alloys

Tan¹

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As the lightest structural metallic materials, magnesium (Mg) alloys have attracted increasing interest in the automotive and aerospace industries. However, low oxidation resistance of Mg alloys limits their wider applications at elevated temperatures. Beryllium (Be) has long been considered as one of the most effective alloying elements in improving the oxidation resistance of Mg alloys even at ppm concentration. However, a convincing mechanism of this unique effect of Be in Mg alloys still remains unclear. Two mechanisms have been proposed. The BeO hypothesis assumes that the BeO layer forms prior to the MgO, whereas the reactive element effect model considers that the segregation of Be 2+ cations along the MgO grain boundaries inhibits the outward diffusion of Mg 2+ cations. Both models have never been experimentally verified. The present work aims to comprehensively investigate the effects of trace additions of Be on the high temperature oxidation behaviour of Mg alloys and, therefore, to understand the mechanism of how Be improves the oxidation resistance of Mg alloys.Be-containing AZ91 alloys were produced with trace additions of Be (10 ppm-60 ppm) into the alloy melt. Thermogravimetric analysis (TGA) and long-term furnace oxidation (LTFO) were used to characterize the oxidation behaviours of the alloys. All results showed that trace additions of Be significantly improved the oxidation resistance of the AZ91 alloy at 400 C, even at 10 ppm. In order to investigate the effectiveness of Be in other Mg alloys, 60 ppm Be was added to Mg-2Zn, Mg-2Sn, Mg-2Y, AS21, AM60, ZK20 and ZC63. Similar to the AZ91 alloy, experimental results showed that microalloying with Be effectively lowered the oxidation rates at 500 C and increased the ignition temperatures of the Mg-2Zn, Mg-2Sn, AS21, and ZC63 alloys. But, Be addition marginally influenced the oxidation behaviours of the ZK20, AM60 and Mg-2Y alloys.In order to understand the mechanisms behind why Be improves the oxidation resistance of cast Mg alloys, the oxidation layers were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nanoindentation. No continuous BeO surface layers were observed on the surfaces of the alloys tested and no Be segregation was detected along the grain boundaries of MgO. However, TEM examination detected the accumulation of Be in the initially formed MgO layer during the oxidation process, which led to the formation of fine-grained (Mg,Be)O solid solutions. As a result, the initially formed surface oxide was effectively strengthened. The nanoindentation and nanoscratch analyses verified that the reinforced (Mg,Be)O layers on the Becontaining AZ91, Mg-2Zn, Mg-2Sn, AS21 and ZC63Be alloys exhibited a higher hardness and strength than the MgO layer on the alloys without Be. Hence, it is considered that during high temperature oxidation, the accumulation of Be on the surface of Mg alloys reinforced the initially XI My special thanks also go to Prof. Fusheng Pan for his insightful advices on my projec...

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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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Effect of be addition on the oxidation behavior of Mg−Ca alloys at elevated temperature

Cited by 38 publications

References 8 publications

Oxidation of magnesium alloys at elevated temperatures in air: A review

Oxidation of magnesium alloys at elevated temperatures in air: A review

Influence of trace addition of Be on the oxidation behaviour of Mg alloys

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

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