Counteraction of particulate segregation during transient liquid-phase bonding of aluminium-based MMC material

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 Μm were segregated when the copper foil thickness exceeded 5 and 15 Μm for the base metals examined. When bonding at 853 K, the liquid widths produced using these copper foil thiciknesses 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 Μm to 2.4 Μm, when the heating rate to the bonding temperature decreased from 1 Ks−1 to 0.01 Ks−1.