DYNAMIC ANALYSIS OF UNIDIRECTIONAL PRESSURE INFILTRATION OF POROUS PREFORMS BY PURE METALS

Unidirectional pressure infiltration of porous preforms by molten meta ls is investigated numerically. A phenomenological model to describe f luid flow and transport phenomena during infiltration of fibrous prefo rms by a metal is formulated. The model describes the dynamics of the infiltration process, the temperature distribution, and solid fraction distribution. The numerical results are compared against classical as ymptotic analyses and experimental results. This comparison shows that end effects may become important and render asymptotic results unreli able for realistic samples. Fiber volume fraction and initial temperat ure appear as the factors most strongly influencing infiltration. Meta l superheating affects not only the length of the two-phase zone but a lso the solid fraction distribution in the two-phase zone. The effect of constant applied pressure, although significant on the infiltration velocity, is almost negligible on the two-phase zone length and on so lid fraction distribution. When the initial preform temperature is bel ow the metal melting point, and constant pressure is applied under adi abatic conditions, the flow ceases when sufficient solidification occu rs to obstruct it. A comparison with literature experiments proves the model to be an efficient predictive tool in the analysis of infiltrat ion processes for different preform/melt systems.