Threshold Pressure For Infiltration Research Articles

Determination of Threshold Pressure for Infiltration of NaCl Preforms by a Zinc Base Alloy and its Effect on Young´s Modulus by Numerical Simulation

Determination of Threshold Pressure for Infiltration of NaCl Preforms by a Zinc Base Alloy and its Effect on Young´s Modulus by Numerical Simulation

Fabrication of Al/TiB2 composites through gas pressure infiltration

Titanium diboride is being evaluated as a replacement of SiC in metal/ceramic composites for thermal management. Albeit these composites are produced by gas pressure infiltration, no study of the process is available. This work presents an analysis of the threshold pressure for infiltration of Al into TiB2 compacts and of the infiltration kinetics. Particles of diameters 14 and 20 μm, and spans of 1.62 and 1.77, were packed obtaining a volume fraction of 0.63. The compacts were infiltrated in air with pure Al at 700 °C. Despite of the fact that the average particle radii differ in a 50%, the threshold pressure for the coarser particles is only a 4% lower, while intrinsic compact permeabilities (derived from infiltration of a wetting organic liquid) are identical. The origin of this apparently odd behavior is the almost identical specific surface areas that those two particles have. Contact angles derived from infiltration experiments are shown to be compatible with sessile drop results.

Wetting and capillarity in the Sn/graphite system

Aiming to investigate the role of wettability in the infiltration of tin into graphite particle compacts, sessile drop and infiltration experiments have been carried out at temperatures in the range of 300–700 °C. The surface tension of liquid tin and the contact angle at the tin/graphite interface have been measured in an argon atmosphere by means of the sessile drop technique, while pressure infiltration of Sn into compacts of graphite particles (27.2 μm of average diameter) has been carried out in air. The results indicate that the threshold pressure for infiltration is proportional to the work of immersion, as predicted by the capillary law. The particle geometric factor derived from the slope of the straight line is similar to that obtained previously from infiltration of aluminum. Although these results may indicate that the oxide layer that covers the tin surface plays a minor role in the infiltration process, a definitive conclusion may require a more detailed analysis of this interesting system.

Wettability in pressure infiltration of SiC and oxidized SiC particle compacts by molten Al and Al-12wt%Si alloy

The infiltration behavior of compacts of SiC particles in two surface conditions, as-received and thermally oxidized, was investigated by using pure Al and Al-12wt%Si as infiltrating metals. Analysis of the threshold pressure for infiltration revealed that the process is governed by the same contact angle for all different systems, no matter the metal or particle condition. This leads to the conclusion that oxidation does not modify the wetting characteristics of the particles, most probably because they are already covered by a thin native oxide layer that remains unaltered in processing routes involving short contact times and low temperatures, such as actual conditions of pressure infiltration at 700 °C.

Reducing Threshold Pressure for Infiltration of Al-12Si Alloys into Carbon Particle Compacts by Placing a Thin Layer of Sn at the Infiltration Front

The oxide layer that usually covers the surface of liquid aluminum and its alloys, is one of the main factors that hinders infiltration of these alloys into graphite particle compacts. The oxide film increases the threshold pressure for infiltration and the porosity of the resulting composites is large because the wetting at the metal/carbon interface is reduced. Infiltrating graphite compacts with tin requires, however, a much lower pressure, less than half of that required to infiltrate the eutectic Al-12Si alloy. As the surface tension of tin is half that of the Al-12Si alloy, this result indicates that wetting at the Sn/C interface is slightly better. As a result, porosity in the infiltrated samples is reduced. In order to reduce the threshold pressure and improve the properties of Al-Si/graphite composites, a novel method has been used in this work that consists in placing a thin film of tin at the compact end through which infiltration takes place. During the infiltration process the graphite particles are firstly infiltrated by tin, which is pushed by the aluminum alloy, thus avoiding the oxidation of the latter. The method proved to be very effective in reducing the threshold pressure, while keeping almost constant the infiltration rate.

超音波含浸法を用いた炭素繊維バンドルへの溶融アルミニウム合金の含浸機構

As the fabricating process of continuous M40J carbon fiber reinforced aluminum alloys composite wires by using ultrasonic infiltration method, the mechanism of the infiltration of molten alloys into the bundle of the carbon fibers was examined especially from the viewpoints of wettability, acoustic cavitation and threshold pressure for infiltration. It was found that the infiltratability of the alloys was proportional to the maximum intensity of the acoustic cavitation. Both the infiltratability and the intensity were enhanced by the addition of surfactant elements for molten aluminum. Thus, decrease in surface tension will cause the generation of acoustic cavitation to increase. When the ultrasonic vibration is applied to molten aluminum alloys, acoustic cavitation would be formed on/in the bundle of carbon fibers. Then the shock wave, which was caused by the cavitation collapsed, would lead to leave the distance between fibers in the bundle. From the results of the direct observation of the bundle in the aqueous solution using high speed camera during applied ultrasonic vibration, the diameter of the bundle was increased by generating the cavitation. Thus, this phenomenon will also cause the decrease in the threshold pressure for infiltration. Therefore, both the generation of the acoustic cavitation and increase in the interval between fibers will be the controlling factors of the infiltration in the fabricating process of this kind of composites by using ultrasonic vibration.

Liquid metal infiltration into ceramic particle preforms with bimodal size distributions

The work carried out during the last years on pressure infiltration of liquid metals into ceramic compacts made of bimodal mixtures of particles is reviewed. The use of bimodal mixtures of particles largely different in size, allows obtaining preforms, and thus, composites, with particle volume fractions V p high enough to be used as supports in electronic packaging. The experimental results for the particle volume fraction are rationalized using a simple model that assumes that small particles can be easily accommodated in the free space left by large particles. Threshold pressure for infiltration P 0 seems to be mainly controlled by the local compactness of fine particles. The experimental results for P 0 can be fitted using the particle surface area per unit volume given by the linear rule of mixtures. The intrinsic permeability of the preforms, evaluated by means of pressureless infiltration of an organic liquid, can be rationalized in terms of models used in soil science. Thermal properties of the composites are also briefly discussed. The coefficient of thermal expansion calculated over a wide temperature range decreases linearly with the particle volume fraction, indicating that the key parameter is V p, while other characteristics of the composite are irrelevant or play a minor role. The experimental results for the thermal conductivity can be accounted for by Hasselman–Johnson formula, using, as above, the particle surface area per unit volume given by the linear mixture rule.

Pressure infiltration of Al and Al-12 wt% Si alloy into compacts of SiC and oxidized SiC particles

Oxidizing SiC particles is a common practice in the fabrication of SiC/Al composites through direct mixing of the liquid metal and the ceramic particles. This practice is addressed to reduce the reaction between the two materials. In a previous work it was concluded that oxidizing SiC particles scarcely affected the threshold pressure for infiltration of pure Al into compacts made of those particles. In this work we present a detailed study of this problem for infiltration of pure Al and the eutectic Al-Si alloy. Our results indicate that oxidizing of SiC particles does not affect significantly either the threshold pressure or the infiltration kinetics. This conclusion is equally valid for both pure Al and the eutectic alloy.

Threshold pressure for infiltration and particle specific surface area of particle compacts with bimodal size distributions

Estimating the average particle specific surface area in compacts made of bimodal particle mixtures by means of the linear rule of mixtures allows to calculate the threshold pressure for liquid metal infiltration into such compacts. Recent experimental data for infiltration of Al into bimodal SiC compacts are analysed using this approach.

Interfacial tensions and threshold pressure for infiltration of packed ceramic particulate by Al-Sn and Al-Pb alloys

Interfacial tensions and threshold pressure for infiltration of packed ceramic particulate by Al-Sn and Al-Pb alloys

Effect of Alloying Additions on Threshold Pressure for Infiltration and Porosity of Aluminium-Based Melt Infiltrated Silicon Carbide Powder Compacts

Effect of Alloying Additions on Threshold Pressure for Infiltration and Porosity of Aluminium-Based Melt Infiltrated Silicon Carbide Powder Compacts

Wettability of binary and ternary alloys of the system Al-Si-Mg with SiC particulates

The authors have presented results of an investigation of wettability of SiC particulates by liquid alloys of the Al-Si-Mg system. The evaluation of wetting has been carried out through the determination of the threshold pressure for infiltration of packed SiC particulates by the liquid alloy. The results indicate that whereas Si and Mg additions do not affect wetting, in the case of the ternary alloys the contact angle decreases in an amount proportional to the content of Mg[sub 2]Si.

マイカセラミックス粒子／アルミニウム複合系の臨界溶浸圧

Wettability of ceramic reinforcements with molten metals plays a vital role in the quality of metal matrix composites (MMCs) fabricated through liquid processing: the poor wettability causes non-infiltrated defects to remain in pressure cast MMCs with a low applied pressure. Threshold pressure for infiltration is one of the promising methods to evaluate wettability, since the reinforcement itself in MMCs can be utilized in this method. The mica-ceramic particles which had been classified into three sizes (L, M, S) were supplied to measure the threshold pressure for molten aluminum infiltration. Pressure infiltrations to the particle preforms were performed at 998K in vacuum or air atmosphere. The threshold pressures for molten aluminum infiltration were found to be 80.9 (L), 77.8 (M) and 159kPa (S) in vacuum, and 96.9 (L), 96.1 (M) and 162kPa (S) in air atmosphere. The lower threshold pressures in vacuum can be ascribed to the better wettability. Non-infiltrated defects with a meniscus configuration were observed in the vicinity of a contact point of two particles. However, flat defects appeared between quasi-tangential planes in MMCs using L-size particle preforms, and aggregate defects were observed in S-size preforms. Modelling the defect with a meniscus configuration to estimate the defect size, the relation between the threshold pressure and the wettability can be derived from the work done by an applied pressure balancing the interfacial energy changes. The contact angle of mica-ceramics with molten aluminum in vacuum is calculated to be approximately 2.39rad which is obtained from the threshold pressure into the M-size particle preforms with less flat or aggregate defects. Hence, the relation between the threshold pressure and the contact angle depends on a configuration of non-infiltrated defects.

Wetting of ceramic particulates with liquid aluminum alloys: Part I. Experimental techniques

An experimental technique for evaluation of wettability of solid particulates with liquid metal was developed. Uniformly packed powder specimens were prepared with a tamping device specially made for the present experiment, and wetting tests were conducted by pressure infiltration of liquid Al-alloys into the powder specimens. The threshold pressure for infiltration was used as a measure of wettability. With this technique, wettabilities were measured for 10 μm diameter SiC and B4C particulates by several Al-based alloys. Threshold pressures obtained from this technique showed reproducibility to approximately ±7 kPa. Microstructures of infiltrated powder specimens indicated planar front infiltration with no disruption of powder compact during infiltration test and virtually no porosity.