The impregnation of a fibrous preform by a liquid metal is one of the techniques
used to prepare metal matrix composites (MMC). The preparation by impregnation may
however lead to defects like microporosity. The micropores present in MMC result from
the superposition of two processes: the trapping of gas by capillarity during the
infiltration phase and the formation of additional porosity related to solidification
shrinkage. These two processes are analyzed in this paper and physical models are
proposed for their description. It is then shown how the formation of microporosities
can be simulated numerically using these models. Finally, prospects for a better numerical
simulation of the preparation of MMC by impregnation are discussed.