THE EFFECT OF PORE-SIZE ON THE INFILTRATION KINETICS OF ALUMINUM IN TITANIUM CARBIDE PREFORMS

Capillaric melt infiltration is a simple and attractive way of fabrica ting metal/ceramic composites. In this work, four different TiC prefor ms of approximately 58% theoretical density, but different pore sizes ranging from about 1 to 30 mum, were produced. These were suspended fr om a Thermo-Gravimetric Analyzer (TGA) and infiltrated with molten Al under flowing Ar. Infiltration profiles were obtained by continuously monitoring the weight change of the preform. These tests were performe d for temperatures ranging from 860 to 1300-degrees-C. Kinetic analysi s on these infiltration profiles yielded activation energies ranging f rom 105 to 450 kJ/mol, depending on the pore size. It is suggested tha t the driving mechanism for the system changes from a diffusion contro lled process for smaller pore sizes, to one which is driven by a surfa ce reaction occurring at the interface for larger pores.