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Abstract
A wide range of copper and tin powder additions to iron powder sintered compacts hasbeen studied. From mechanical-property tests it has been shown that when using sinteririg temperatures of 900–1100°C in nitrogen/10% hydrogen atmospheres there is an optimum copper: tin ratio of 15:2. The mechanical properties obtained from compacts pressed from iron mixed with 4% copper+tin in this ratio and sintered at 900°C were similar to those obtained from iron −l0% copper powder compacts sintered at 1100°C. Moreover, the iron-copper-tin components showed improved dimensional accuracy.
In a further series of experiments, it was shown that tin additions to iron-copper alloy compacts increased the solubility of iron in the liquid phase at the sintering temperature and simultaneously decreased the rate of diffusion of copper into the iron particles. At the same time, tin improved the wettability of the liquid, reducing its surface tension and allowing it to disperse more completely throughout the matrix. The mechanical properties of compacts containing larger amounts of tin were decreased by the presence of brittle compounds, although the sintering rate was increased. It is concluded that the optimum properties of iron-copper-tin compacts are obtained by making correct additions of copper and tin to the iron powder and giving careful consideration to the sintering atmosphere.
Notes
* Manuscript received 7 May 1973. Contribution to a Symposium on ‘PM Alloys and Properties’, to be held in Eastbourne on 19–21 November 1973.