In the previous paper, we confirmed that the Fe-8.0%Cu-C ternary mixed powder compacts containing more than 0.8%C, and the Fe-Cu-1.0%C ternary mixed powder compacts containing more than 4.0%Cu showed shrinkage on heating at the temperature higher than 1090°C.
In this experiment, a study of the elimination mechanism of the abnormal expansion by graphite addition was carried out mainly from the viewpoint of the Fe-Cu-C ternary equilibrium.
The results obtained were as follows:
(1) The Fe-8.0%Cu-C ternary mixed powder compacts containing up to 0.6%C showed only one endothermic peak due to Cu melting at 1083°C during the heating process. However, in the specimen containing more than 0.8%C, another endothermic peak due to the ternary monotecto-eutectic reaction at 1095°C was observed, in addition to the above mentioned endothermic peak.
During the cooling process, the Fe-8.0%Cu binary mixed powder compacts showed, no exothermic peak due to solidification. While the Fe-8.0%Cu-C ternary mixed powder compacts containing up to 0.6%C showed the exothermic peak due to the solidification of Cu at 1083°C, the specimens containing more than 0.8%C showed the exothermic peak due to the ternary monotecto-eutectic reaction.
(2) The Fe-Cu-1.0%C ternary mixed powder compacts containing 3.0%Cu showed only one endothermic peak due to Cu melting at 1083°C during the heating process. The specimens containing more than 4.0%Cu showed another endothermic peak due to the ternary monotectoeutectic reaction at 1095°C, besides the peak due to Cu melting.
During the cooling process, as for the specimens containing up to 4.0%Cu, no exothermic peak due to solidification was observed, while the specimens containing more than 6.0%C showed the exothermic peak due to the ternary monotecto-eutectic reaction at 1095°C.
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