Activation of alumina foams for fabricating MMCs by pressureless infiltration

Lemster, K.; Delporte, Marc; Graule, Thomas; Kuebler, Jakob

doi:10.1016/j.ceramint.2006.04.002

Cited by 35 publications

(24 citation statements)

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“…In systems studied so far, such as SiC and AlN preforms infiltrated by bronze and Fe-base alloys, the enhancement of the wettability is due either to the formation of a wettable layer through the reaction of the activator with the ceramic substrate or to the lowering of the surface tension of the melt. Activation by Ti has been successfully used for the manufacturing of Al 2 O 3 -X3CrNiMo13-4 MMC, [4][5][6][7] but textural observations and the linear infiltration kinetics observed in preliminary experiments are difficult to explain with the formation of reaction layer or the lowering of surface tension. [8][9][10][11][12][13][14][15] Two types of experiments were, therefore, set up to elucidate the infiltration mechanisms in the alumina -steel system.…”

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“…Different manufacturing techniques such as squeeze casting, pressure infiltration or powder metallurgy have been described in previous studies. [1][2][3][4] MMC's made of Al 2 O 3 (alumina) and high melting Fe-base alloys (e.g., X3CrNiMo13-4) meet the requirements for certain application in food, pharmaceutical and automotive industry. [5] A formfree and advantageous way to produce MMC's is the infiltration of porous ceramic performs by metal melts.…”

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Experimental Models for Activtation Mechanism of Pressureless Infiltration in the Non‐Wetting Steel‐Alumina MMC System

et al. 2008

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Common activation mechanisms, which are responsible for infiltration in other non‐wetting systems, play only a secondary role in the Ti activated Al2O3/X3CrNiMo13‐4 system for pressureless alloy infiltration into porous ceramic preforms. Experiments with a model pore consisting of two juxtaposed parallel alumina plates with lithographically imprinted arrays of Ti‐dots show that transport through the vapour phase and subsequent condensation of the steel components onto the activator are the key steps of the activation mechanism. The mechanism was additionally confirmed by infiltration experiments with porous alumina preforms consisting of alternating layers with and without Ti parallel to the infiltration direction. Only layers with activator particles were infiltrated.

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Experimental Models for Activtation Mechanism of Pressureless Infiltration in the Non‐Wetting Steel‐Alumina MMC System

et al. 2008

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“…In addition the wetting of ceramics by metal melts can be improved by changing the chemistry of the metal/ceramic interface. Adding pure active metal particles such as titanium to the ceramic surface or distributing them directly in the ceramic preform enables the pressureless wetting of ceramics by metal melts [10,11]. The beneficial effect on wetting by titanium has been recognised for a long time.…”

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Mechanical properties of three-dimensional interconnected alumina/steel metal matrix composites

et al. 2009

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Three-dimensional interconnected alumina/ steel metal matrix composites (MMCs) were produced by pressureless Ti-activated melt infiltration method using three types of Al 2 O 3 powder with different sizes and shapes. By partial sintering during infiltration an interpenetrating ceramic network was realised. The effect of the ceramic particle size and shape on the resulting ceramic network, volume % fraction and the MMC properties is presented. The MMCs were characterised for mechanical properties at room temperature and elevated temperature. An increase in flexural strength and Young's modulus with decreasing particle size has been observed. In addition, the effect of the volume of ceramic content and the surface finish of the MMCs on the wear behaviour is shown.

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“…The choice of a suitable manufacturing route is conditioned by cost factors, form flexibility and production temperature, [3,4] For certain applications in the food, pharmaceutical and automotive industry, the required properties are best met by composites made of alumina (Al 2 O 3 ) and high-melting Fe-based alloys (>1400 8C) such as X3CrNi13-4. [5][6][7][8][9] Pressureless infiltration would be the manufacturing route of choice for many of these applications, but the alumina-steel system lacks an important prerequisite, that makes infiltration without pressure possible: Oxide ceramics in general, due to their ionic character, show bad wettability by metal melts. The equilibrium contact angle u Y , which depends on the surface tensions of the phases involved, is given by Young's equation [10][11][12] (Eq.…”

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Activation Mechanism and Infiltration Kinetic for Pressureless Melt Infiltration of Ti Activated Al₂O₃ Preforms by High Melting Alloy

Vasic¹,

Grobéty²,

Kuebler³

et al. 2009

Adv Eng Mater

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Metal matrix composites (MMC) represent a class of materials of broad technological and commercial significance designed for applications where the contrasting material properties of both metals and ceramics are needed. [1] MMC combine the high strength and wear resistance of ceramics with the ductility as well as the thermal and electrical conductivity of metals. The ceramic phase within the metal matrix guarantees a failure-tolerant behavior and low thermal expansion. [2] Many fabrication routes have been described in previous studies, [3] the most important ones are pressureless and pressure assisted metal melt infiltration techniques as well as powder metallurgical methods. The choice of a suitable manufacturing route is conditioned by cost factors, form flexibility and production temperature, [3,4] For certain applications in the food, pharmaceutical and automotive industry, the required properties are best met by composites made of alumina (Al 2 O 3 ) and high-melting Fe-based alloys (>1400 8C) such as X3CrNi13-4. [5][6][7][8][9] Pressureless infiltration would be the manufacturing route of choice for many of these applications, but the alumina-steel system lacks an important prerequisite, that makes infiltration without pressure possible: Oxide ceramics in general, due to their ionic character, show bad wettability by metal melts. The equilibrium contact angle u Y , which depends on the surface tensions of the phases involved, is given by Young's equation [10][11][12] (Eq. 1):and is in general well over 908 for such systems. [13][14][15][16] It is therefore not surprising that steel melts do not wet alumina surfaces.Pressure assisted infiltration and previous activation of the metal and/or the ceramic preform by incorporating reactive metals like titanium (Ti) are the two methods at disposal to circumvent the wettability problem. [2,7] Moreover, it was shown that a pressure drop within preforms, caused by the reaction of reactive metals such as e.g. Ni, Ti or Al and thus generation of a vacuum atmosphere is favorable for successful infiltration. [17] Applying pressure to the melt allows overcoming the negative capillary forces, but the pressurizing systems are technically demanding. The addition of a reactive element such as Ti enhances the infiltration performance either by lowering the surface tension of the metal melt and/or by the reactive modification of the ceramic surface. [18] It is well known that the addition of Ti to brazing solders for joining ceramic components lowers the contact angle of the metal melt with alumina due to the formation of a reactive layer. [19,20] Addition of titanium to steel melts lowers the surface tension, although there is a large spread in the data which are due to the presence or absence of surface active species in the gas phase. The formation of a TiO x reactive layer, and also modification of fluid flow and active metal adsorption are additional mechanisms that have been postulated to enhance wettability. [21,22] The activator may be prealloyed into the metal or dis...

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Activation of alumina foams for fabricating MMCs by pressureless infiltration

Cited by 35 publications

References 14 publications

Experimental Models for Activtation Mechanism of Pressureless Infiltration in the Non‐Wetting Steel‐Alumina MMC System

Experimental Models for Activtation Mechanism of Pressureless Infiltration in the Non‐Wetting Steel‐Alumina MMC System

Mechanical properties of three-dimensional interconnected alumina/steel metal matrix composites

Activation Mechanism and Infiltration Kinetic for Pressureless Melt Infiltration of Ti Activated Al₂O₃ Preforms by High Melting Alloy

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Activation of alumina foams for fabricating MMCs by pressureless infiltration

Cited by 35 publications

References 14 publications

Experimental Models for Activtation Mechanism of Pressureless Infiltration in the Non‐Wetting Steel‐Alumina MMC System

Experimental Models for Activtation Mechanism of Pressureless Infiltration in the Non‐Wetting Steel‐Alumina MMC System

Mechanical properties of three-dimensional interconnected alumina/steel metal matrix composites

Activation Mechanism and Infiltration Kinetic for Pressureless Melt Infiltration of Ti Activated Al2O3 Preforms by High Melting Alloy

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Activation Mechanism and Infiltration Kinetic for Pressureless Melt Infiltration of Ti Activated Al₂O₃ Preforms by High Melting Alloy