Sinter-joining of different metal powder compacts using resistance heating

Feasibility of sinter-joining method making use of resistance heating with an adiabatic feature was examined. Modeled experiments were conducted using pure metal powders of chromium, iron, nickel, copper and aluminum with a wide variety of melting points or sintering temperatures. All pairs of green compacts were sinter-joined varying compacting pressure and electrifying voltage at fixed electrifying time of 1 s, and their sinter-joining performances were rated by visual inspection and optical microscope observation of vertical section across the joining interface. The results were as follows. Most of the pairs were successfully sintered and joined under properly arranged conditions of electrifying voltage and compacting pressures, but in the combination of chromium and aluminum with a large melting point difference, the aluminum compact melted and infiltrated into the openings of the chromium compact, and in the combinations of chromium and iron with copper with high thermal conductivity, the sintered compacts of chromium and iron had both a porous structure near the joining interface. Those undesirable phenomena were, however, suppressed considerably by employing more rapid heating measures. It was concluded that the sinter-joining method using resistance heating has not a little feasibility.