Kinetics of directed oxidation of Al-Mg alloys in the initial and final stages of synthesis of Al2O3/Al composites

Venugopalan, H. S.; Tankala, K.; DebRoy, T.

doi:10.1016/0921-5093(95)10072-5

Cited by 27 publications

(21 citation statements)

References 20 publications

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“…On heating to 850 ° C, the gap was filled by an oxidation layer that formed and then grew on the Al alloy surface. The sequence of the Al alloy oxidation in the gap has been discussed in detail elsewhere and is considered widely to occur through the following four steps: At low temperatures, Al oxidizes to form an Al 2 O 3 layer on the surface of the Al alloy and it grows in thickness with increasing temperature to 850°C. At higher temperatures, Mg in the Al alloy reduces Al 2 O 3 to Al and the free oxygen reacts with Mg to form a thin MgO layer. As the MgO grows on the surface of the Al alloy, the Mg activity in the Al alloy decreases and thus the relative Al concentration increases.…”

Section: Discussionmentioning

confidence: 99%

Interfacial Reactions Between Anorthite (CaAl₂Si₂O₈) and Al 7075 Alloy at 850°C and 1150°C

et al. 2016

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The present work reports an investigation of the interactions of Al 7075 alloy and anorthite at 850°C (150 h) and 1150°C (24 h). Transmission electron microscopy, electron probe microanalysis, X-ray diffraction, and scanning electron microscopy coupled with energy-dispersive spectroscopy were used to identify the mineralogical and microstructural changes at the metalceramic interface. At 850°C, the phase formation mechanisms were (

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Section: Discussionmentioning

confidence: 99%

Interfacial Reactions Between Anorthite (CaAl₂Si₂O₈) and Al 7075 Alloy at 850°C and 1150°C

et al. 2016

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“…In the cup test, the sequence of surface reactions of Al alloy (containing Mg and Zn) with air in the gap, as shown in Fig. (a), is believed to occur through the following steps: Al oxidizes to form an alumina layer on the surface of the alloy. This layer grows in thickness with increasing heating temperature to 850°C. Mg present in the alloy reduces alumina to form magnesia.…”

Section: Discussionmentioning

confidence: 99%

“…In the cup test, the sequence of surface reactions of Al alloy (containing Mg and Zn) with air in the gap, as shown in Fig. 8(a), is believed to occur through the following steps: [28][29][30][31][32][33][34] 1. Al oxidizes to form an alumina layer on the surface of the alloy.…”

Section: <50 Lm Thickness Interdiffusion Zone Chemically Closementioning

confidence: 99%

Interfacial Reactions Between BaAl₂Si₂O₈ and Molten Al Alloy at 850°C

et al. 2015

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A corrosion cup test was undertaken using BaAl 2 Si 2 O 8 and Al4.1Zn3.2Mg alloy, heated in air for 150 h at 850°C. Electron probe microanalysis, X-ray diffraction, and scanning electron microscopy coupled with energy dispersive spectroscopy were used to identify the mineralogical and microstructural changes at the interfaces. The microstructural results revealed three microstructural areas: (1) Spinel layer with large numbers of Al alloy channels; (2) interfacial area with mainly alumina, spinel, and BaAl 2 Si 2 O 8 ; and (3) interdiffusion zone chemically close to barium hexaaluminate. The principal observations are:1. BaAl 2 Si 2 O 8 was highly resistant to molten Al alloy corrosion owing to sluggish kinetics, as evidenced by the observation of unreacted BaAl 2 Si 2 O 8 grains in the interfacial area. 2. The nature of the microstructure, particularly an interdiffusion zone instead of a continuous layer of precipitated alumina at the interface between the Al alloy channels and the unreacted BaAl 2 Si 2 O 8 supports the conclusion that the corrosion mechanism is governed by interdiffusion (Si/Ba and Al/Mg) and substitution. 3. The formation and limited retention of an MgO layer at the metal-ceramic interface played a critical role in alloy oxidation and the consequent interfacial phenomena.

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“…MgAl 2 O 4 layer. Kinetics laws cannot be straightforwardly deduced from thermogravimetry analyses performed on powder samples; nevertheless, the slow increase observed in the weight gain obtained at low temperature (350 and 365°C) suggests that the amorphous spinel phase formed at these temperatures can act as a diffusion barrier and decrease the oxide layer growth rate, as already observed in the literature [7,26,28,31]. Reversely, the sharp acceleration in the weight gain curve which is observed at 411°C (see Fig.…”

Section: Discussionmentioning

confidence: 67%

“…However, in view of the high porosity of the oxide scale and the large content in magnesium of the substrate alloy, depletion of magnesium at the interface between the alloy and the oxide layer and accumulation of voids seem unlikely in our case as the bulk alloy can act as an infinite Mg reservoir. An alternative explanation for enhanced oxidation rates at 8 h would be the nucleation of a new phase between the alloy substrate and the oxide film [1,23,24,26,32]. Although preferential oxidation of magnesium is kinetically favoured at the start of the oxidation process (phase 1) due to the high vapour pressure of this metal, the formation of an intermediate spinel layer MgAl 2 O 4 is also possible in view of thermodynamic considerations and has often been observed during oxidation of Al-Mg alloys.…”

Section: Discussionmentioning

confidence: 96%

High Temperature Oxidation of the Al3Mg2 Complex Metallic Alloy

et al. 2009

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International audienceHigh temperature air oxidation of the Al3Mg2 complex metallic alloy was investigated on powder samples and bulk polycrystals in the temperature range 350–420 °C by thermogravimetric measurements, SEM and TEM. Oxidation at 420 °C on the polycrystalline samples comprised three successive phases characterised by linear kinetics laws. The first stage corresponded to the formation of a porous non adherent nanocrystalline MgO scale having a cauliflower morphology. A first acceleration in the kinetics law was ascribed to the nucleation and growth of MgAl2O4 crystallites which form a thin (~10 nm) film at the interface between the substrate alloy and the MgO top layer. A new linear regime was observed in the oxidation process corresponding to diffusion of magnesium through the grain boundaries of the spinel film and through the porous MgO layer. Finally, fragmentation and cracking of the scale leads to a further acceleration followed by a new linear regime

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Kinetics of directed oxidation of Al-Mg alloys in the initial and final stages of synthesis of Al2O3/Al composites

Cited by 27 publications

References 20 publications

Interfacial Reactions Between Anorthite (CaAl₂Si₂O₈) and Al 7075 Alloy at 850°C and 1150°C

Interfacial Reactions Between Anorthite (CaAl₂Si₂O₈) and Al 7075 Alloy at 850°C and 1150°C

Interfacial Reactions Between BaAl₂Si₂O₈ and Molten Al Alloy at 850°C

High Temperature Oxidation of the Al3Mg2 Complex Metallic Alloy

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Kinetics of directed oxidation of Al-Mg alloys in the initial and final stages of synthesis of Al2O3/Al composites

Cited by 27 publications

References 20 publications

Interfacial Reactions Between Anorthite (CaAl2Si2O8) and Al 7075 Alloy at 850°C and 1150°C

Interfacial Reactions Between Anorthite (CaAl2Si2O8) and Al 7075 Alloy at 850°C and 1150°C

Interfacial Reactions Between BaAl2Si2O8 and Molten Al Alloy at 850°C

High Temperature Oxidation of the Al3Mg2 Complex Metallic Alloy

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Interfacial Reactions Between Anorthite (CaAl₂Si₂O₈) and Al 7075 Alloy at 850°C and 1150°C

Interfacial Reactions Between Anorthite (CaAl₂Si₂O₈) and Al 7075 Alloy at 850°C and 1150°C

Interfacial Reactions Between BaAl₂Si₂O₈ and Molten Al Alloy at 850°C