Particle segregation during transient liquid-phase bonding of aluminium-based metal matrix composite material using copper filler metal was investigated. Segregation was promoted by the slow movement of the solid-liquid interface during isothermal solidification and alumina particles with diameters less than 30 mu m were segregated when the copper foil thickness exceeded 5 and 15 mu m for the base metals examined. When bonding at 853 K, the liquid widths produced using these copper foil thicknesses were almost identical to the median inter-particle spacing in the base metals investigated. When the amount of liquid formed at the bonding temperature decreased below a critical level, the test specimens broke apart immediately following the joining operation. The minimum film thickness of copper for satisfactory joint strength increased from 0.6 mu m to 2.4 mu m, when the heating rate to the bonding temperature decreased from 1 Ks(-1) to 0.01 Ks(-1).