Cu-Al系焼結合金に関する研究(第1報) : 焼結中に現われる異常発熱について

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Aluimium bronze is one of the most useful copper alloys owing to its high strength and high corrosion resistance. However, it has scarcely been used as sintering materials. The present experiments were carried out in order to find what are the difficulties of the sintering of Cu-Al compacts and how to weed out these evils. For this purpose the dilatometric analysis, thermal analysis, microscopic examination and thermochemical calculation were carried out systematically using Cu-Al binary compacts which contain up to 67wt% Al. Results obtained in these experiments were as follows : 1) Independent of Al-content in the Cu-Al compacts, an abnormal expansion appeared constantly at 548°C during sintering, which is the eutectic temperature of Cu-Al binary system. 2) The abnormal expansion increased with the increase of Al-content in the compacts up to 17wt% Al, at higher contents decreased with increase of Al-content, and finally disappeared at the eutectic composition of 67wt% Al. 3) The thermal analysis showed that the abnormal expansion was always accompanied by an abrupt exothermic reaction, led by a slight endothermic reaction of the eutectic. Judging from the direct measurement of the exothermic change, the abnormal expansion seems to be induced mainly by the exothermic reaction above 548°C. 4) The largest abnormal expansion and exothermic change were found in the compact containing about 17wt % Al, which corresponds to the composition of γ 2 phase. 5) From the microscopic examination and thermochemical calculation this exothermic change could be regarded as the heat of γ 2 formation, where Cu powder and Al powder combined catalytically in the presence of a liquid phase at 548°C or above during sintering. In order to weed out this exothermic reaction, Cu-γ 2 compacts should be used for sintering. However, the difficulty of sintering may be expected in this case.
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Cu-Al系焼結合金に関する研究(第1報) : 焼結中に現われる異常発熱について

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