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A study of infiltration in metallic systems. Parkinson, Frederick Lloyd

Abstract

Porous skeletons prepared by sintering loose metal powders have been infiltrated with liquid metals. The systems investigated were nickel-lead, nickel-silver, nickel-copper, iron-copper, iron-silver and iron-silver/copper. Contact angle experiments for the above systems were also performed using the sessile drop technique. It was found that the resultant density of the infiltrated composite depends directly upon the amount of previous deoxidation of the skeleton and also the shrinkage porosity which results from solidification of the molten infiltrant. It was found that the thermodynamic driving force for infiltration is the product ɣlvcos Θ where ɣlvcosΘ = ɣsv -ɣsl. In the systems in which infiltration occurred the contact angle was less than 28° usually being much lower but not zero. In silver-iron system where the contact angle is 36°, infiltration did not occur at all. The infiltration of silver-copper alloys into an iron skeleton was more favourable as the copper content was increased. This was shown to be due to the fact that ɣlvcos Θ increases as the copper concentration increases. In order to determine the rate of infiltration experiments were performed whereby the drop in height of a molten column of infiltrant as a result of infiltration was measured with movie camera. Infiltration was very rapid as porous skeletons of the order of 5 cm in length were infiltrated in less than 0.3 sec. The height of infiltration was found to be proportional to the square root of time and the rate of infiltration, d h/ d t, decreased rapidly with time of infiltration.

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