Abstract
Phenomena appearing during sintering processes of the iron-tin-copper compacts admixed with 2.5 wt% of prealloyed and mixed powders having a Sn/Cu ratio of 35/65 were investigated.
The results obtained are as follows;
1) When the Fe-(0.87 Sn-1.63 Cu) compact admixed with the prealloyed powder is heated, the prealloyed powder particles are melted at about 1010K (737°C), and the liquid penetrates into the iron powder skelton. With rising temperature up to about 1163K (890°C), a little amounts of tin and copper also diffuse from the liquid into the iron, so that the sintered compact expands slightly. Most of the liquid therefore, lies around the neck of the iron skelton. Moreover, the composition of the liquid is more copper-rich than the initial Sn/Cu ratio, because the diffusional coefficient of tin into iron is higher than that of copper. Consequently, the sintered compact has much higher strength than the iron compact even at a low sintering temperature of 1163K (890°C).
2) When the Fe-0.87 Sn-1.63 Cu compact admixed with tin-copper mixed powders is heated, the tin powder particles are melted at 505K (232°C), and the liquid begins to penetrate into the iron powder skelton above 673K (400°C). Most of the liquid reacts with copper powder particles existing separately in the skelton, and becomes a tin-copper alloy, which has the same composition as the prealloyed powder used in 1) before reaching 1023K (750°C), because the tin liquid reacts more easily with copper than iron. Consequently, the properties of sintered compact admixed with the mixed powders is similar to that of the prealloyed powder.
