Understanding the high temperature oxidation and ignition behaviour of two-phase Mg–Nd alloys and a comparison to single phase Mg–Nd

Aydin, D.S.; Hoseini, Majid; Pekguleryuz, Mihriban

doi:10.1080/14786435.2014.998735

Cited by 14 publications

(10 citation statements)

References 30 publications

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“…The ignition temperature of Mg increased with increasing Sr content. Redrawn from Aydin [46,147,178,180] and used with permission of Springer. AZ91-1.5Ca AZ91-1.5Ca-0.5Y AZ91-20ppmBe AZ91-60ppmBe Figure 25: Oxidation kinetics of AZ91-1.5Ca, AZ91-1.5Ca-0.5Y, AZ91-20 ppm (wt) Be and AZ91-60 ppm (wt) Be at 400 C in air for 300 min.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, the lower melting temperature of the eutectic microstructure also contributes to the oxidation. Furthermore, in the molten state, as the Nd content increases, the formation of Nd2O3 causes local depletion of Nd in the liquid subsurface, leading to Mg vaporisation and ignition [147]. Thus, constant or even reversed oxidation resistance was observed at higher Nd content (above 2.5 wt.%) in both the solid and the molten state.…”

Section: Cementioning

confidence: 90%

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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: Discussionmentioning

confidence: 99%

Section: Cementioning

confidence: 90%

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

et al. 2016

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“…Recent years have seen several studies devoted to developing ignition‐resistant Mg alloys with alloying additions . Those studies focused on the addition of alloying elements to Mg commercial alloys, the testing of binary Mg alloys, or the development of higher order systems using a variety of AE and/or RE elements.…”

Section: Introductionmentioning

confidence: 99%

The Ignition Behavior of a Ternary Mg–Sr–Ca Alloy

Villegas-Armenta

Pekguleryuz

2020

Adv Eng Mater

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In this work, a Mg-Sr-Ca alloy is evaluated for ignition resistance. The simultaneous use of Sr and Ca results in an ignition temperature increase of %110 C compared to pure Mg. This is attributed to the formation of a compact oxide scale due to the modification of the native MgO scale. A new parameter, the effective Pilling-Bedworth ratio (EPBR), which is the molar volume ratio between the oxide formed and the substrate alloy, is developed. The EPBR of the composite oxide forming on the Mg-Ca-Sr alloy is found to be greater than 1, resulting in a protective scale due to the increased volume occupied by the oxide at the surface. In the solid state, the oxide scale is rich in CaO, with the SrO contribution being minimal. In the liquid state, SrO contribution increases. MgO:CaO % 1:15 MgO:CaO % 1:1 MgO:CaO % 4:1 MgO:CaO % 2:1 CaO:MgO:SrO % 32:16:1 CaO:SrO % 10:1 EPBR % 0.84 EPBR % 0.97 EPBR % 1.05 EPBR % 1.01 EPBR % 1.03 EPBR % 1.16 670 C, 15 min M/O interface (1000 nm) Middle oxide (500 nm) G/O interface CaO:MgO:SrO % 4:40:3 CaO:MgO:SrO % 3:16:2 CaO:MgO:SrO % 5:1:9 EPBR % 0.85 EPBR % 0.89 EPBR % 1.33

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“…The first group has pure Mg as a reference alloy, and considers the alloying elements Al and [46,147,178,180] and used with permission of Springer.…”

Section: Az91-5camentioning

confidence: 99%

“…Furthermore, in the molten state, as the Nd content increases, the formation of Nd2O3 causes local depletion of Nd in the liquid subsurface, leading to Mg vaporisation and ignition [147]. Thus, constant or even reversed oxidation resistance was observed at higher Nd content (above 2.5 wt.%) in both the solid and the molten state.…”

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confidence: 99%

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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Understanding the high temperature oxidation and ignition behaviour of two-phase Mg–Nd alloys and a comparison to single phase Mg–Nd

Cited by 14 publications

References 30 publications

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

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

The Ignition Behavior of a Ternary Mg–Sr–Ca Alloy

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

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