Influence of oxygen partial pressure on the wetting behaviour in the system Al/Al2O3

John, Heather A. W. St; Hausner, H.H.

doi:10.1007/bf01728687

Cited by 89 publications

(30 citation statements)

References 4 publications

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“…[16] At temperatures above T w , the oxide on the droplet might be destroyed in vacuum due to (1) the formation of the volatile suboxide, Al 2 O, by the reaction 4Al (1) ϩ Al 2 O 3 (s) → 3Al 2 O (g), and (2) partial dissolution of Al 2 O 3 skin in molten Al drop. [17] Even at as low a temperature as 973 K, John and Hausner [14] observed a low contact angle of about 90 deg under very low oxygen partial pressures. On the other hand, at higher temperatures (T Ͼ 1273 K), sapphire is chemically etched by molten Al, resulting in the formation of "ring"-shaped concentric grooves on sapphire [10] ; the formation of these rings is accompanied by cyclic spreading and contraction of the Al droplet with the contact angle, , oscillating between ϳ45 and ϳ80 deg in the temperature range 1473 to 1623 K. [2] The addition of alloying elements to the melt and modification of the substrate through deposition of surface coatings can affect the wettability.…”

Section: Introductionmentioning

confidence: 99%

The effect of temperature, matrix alloying and substrate coatings on wettability and shear strength of Al/Al2O3 couples

Sobczak¹,

Książek²,

Radziwill³

et al. 2004

Metall Mater Trans A

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A fresh approach has been advanced to examine in the Al/Al 2 O 3 system the effects of temperature, alloying of Al with Ti or Sn, and Ti and Sn coatings on the substrate, on contact angles measured using a sessile-drop test, and on interface strength measured using a modified push-off test that allows shearing of solidified droplets with less than 90 deg contact angle. In the modified test, the solidified sessile-drop samples are bisected perpendicular to the drop/Al 2 O 3 interface at the midplane of the contact circle to obtain samples that permit bond strength measurement by stress application to the flat surface of the bisected couple. The test results show that interface strength is strongly influenced by the wetting properties; low contact angles correspond to high interface strength, which also exhibits a strong temperature dependence. An increase in the wettability test temperature led to an increase in the interface strength in the low-temperature range where contact angles were large and wettability was poor. The room-temperature shear tests conducted on thermally cycled sessile-drop test specimens revealed the effect of chemically formed interfacial oxides; a weakening of the thermally cycled Al/Al 2 O 3 interface was caused under the following conditions: (1) slow contact heating and short contact times in the wettability test, and (2) fast contact heating and longer contact times. The addition of 6 wt pct Ti or 7 wt pct Sn to Al only marginally influenced the contact angle and interfacial shear strength. However, Al 2 O 3 substrates having thin (Ͻ1 m) Ti coatings yielded relatively low contact angles and high bond strength, which appears to be related to the dissolution of the coating in Al and formation of a favorable interface structure.

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Section: Introductionmentioning

confidence: 99%

The effect of temperature, matrix alloying and substrate coatings on wettability and shear strength of Al/Al2O3 couples

Sobczak¹,

Książek²,

Radziwill³

et al. 2004

Metall Mater Trans A

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“…[5] The Al/Al 2 O 3 system has been also extensively investigated by a sessile drop technique. [6][7][8][9][10][11][12][13][14] As in the previous case, at low temperatures (<1173 K), the nonwetting behavior in this system was attributed to the presence of a very thin alumina film at the surface of aluminum drop, while improved wetting at elevated temperatures was attributed to the reduction of this layer by liquid Al and the formation of the gaseous aluminum suboxide phase (Al 2 O).…”

Section: Introductionmentioning

confidence: 76%

Interfacial Chemical Interactions in the (Alumina/Graphite/Al Alloys) System: Thermodynamic Modeling and Experimental Results

Gelbstein

Edry

Froumin

et al. 2009

Metall Mater Trans A

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The stability of alumina-coated graphite couples in liquid Al is investigated in the 1373 to 1573 K temperature range. A thermodynamic model was carried out to determine the mechanisms controlling the couple stability and the effect of alloying Al with high melting point element for instance U (up to 3 at. pct). It was established that the dissolved uranium dose not play any role in the interfacial interactions and that the couple stability is governed by the interactions with Al resulting in the release of gaseous products. The experiments focused on wetting kinetics under conditions allowing for an in-situ reduction of the alumina coating by the liquid Al. The experimental results confirm the predictions of the thermodynamic analysis.

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“…John and Hauser [20] published measurements for contact angles between liquid aluminum and aluminum oxide at an extremely low oxygen partial pressure. They found that at 700 °C and , the contact angle is near 90 deg.…”

Section: B Oxide Strengthmentioning

confidence: 99%

Oxide skin strength on molten aluminum

Syvertsen

2006

Metall Mater Trans B

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The oxide skin strength on molten aluminum has been measured as a function of temperature for pure aluminum and some aluminum alloys. The measured values fit well to previous published data of surface tension of liquid aluminum, lg , combined with the wetting angle, , and the mechanical strength of the oxide. It is assumed that the work per area needed to stretch and rupture the oxide skin is a sum of the interfacial tensions and tensile strength of oxide, times oxide thickness:The work per area calculated from previous published data fits reasonably well with the oxide skin strength measurements presented here. It is found that above about 750 °C, the oxide skin strength increases with increasing temperature. The effect of sodium addition to industrially pure aluminum has also been investigated. Addition of 68 ppm sodium increases the oxide skin strength by 52 pct. Addition of 0.3 pct magnesium to Al-11Si reduces the oxide skin strength by 30 to 35 pct below 620 °C. ϭ s lg (1 ϩ cosu) ϩ t и d W ϭ s sg ϩ s lg Ϫ s sl ϩ t и d

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Influence of oxygen partial pressure on the wetting behaviour in the system Al/Al2O3

Cited by 89 publications

References 4 publications

The effect of temperature, matrix alloying and substrate coatings on wettability and shear strength of Al/Al2O3 couples

The effect of temperature, matrix alloying and substrate coatings on wettability and shear strength of Al/Al2O3 couples

Interfacial Chemical Interactions in the (Alumina/Graphite/Al Alloys) System: Thermodynamic Modeling and Experimental Results

Oxide skin strength on molten aluminum

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