In 90Cu-10Sn alloy pore formation during sintering and effect of Sn powder size on porosity and pore size distribution have been studied. To investigate the pore formation process, the compacts of -22+36 μm irregular Cu powder and about 130 μm dia. Spherical Sn powder mixture were sintered at various temperatures. When the sintering temperature was above the melting temperature of Sn (232℃), the liquid Sn began to flow into the capillaries between Cu powders. As the sintering temperature reached 400℃, the liquid Sn had flowed into the capillaries completely, and the original Sn powder sites remained large pores. Untill 500℃ Sn atoms diffused little into Cu particles, but Cu atoms dissolved and diffused into liquid Sn. At 700℃, recrystallization to α-bronze had begun and the specimen composition became almost uniform. At 800℃ large α-grains with many twin boundaries and grown and sphroidized pores resulted.
To investigate the effect of Sn powder size on porosity and pore size distribution, four kinds of mixtures of -22+36 μm irregular Cu powder and about (a) 30 μm, (b) 60 μm, (c) 100 μm, (d) 130 μm dia. Spherical Sn powders were prepared. And the four green compacts were sintered simultaneously at 830℃ for 15 min.
As Sn powder size increased from 30 μm to 60 μm, the porosity increased about from 30 vol.% to 50 vol.%. But the porosity remained constant at about 50 vol.% despite of further increase of Sn powder size. An Sn powder size increased, pore growth and spheroidizing phenomena were pronounced and consequently the number of fine pores decreased steeply and that of large pores increased.