Abstract
Using mixed powder compacts of Fe-8.0%Cu-C ternary system with different graphite contents, and Fe-Cu-1.0%C ternary system with different Cu contents, a study of the effect of graphite content on the elimination of the abnormal expansion during the heating process of the Fe-Cu binary mixed powder compacts was carried out mainly by the differential dilatometric method.
The results obtained were as follows:
(1) In the mixed powder compacts of the Fe-8.0%Cu-C ternary system with graphite contents up to 0.6%, the abnormal expansion persisted through out the sintering process in the γ region, although the amount of expansion was smaller than that of the Fe-8.0%Cu binary system.
However, the specimens with the graphite content more than 0.8% showed a maximum expansion at a temperature slightly higher than 1090°C and then shrank at higher temperatures.
(2) Dimensional change of the Fe-8.0%Cu-C ternary compacts subjected to isothermal sintering at 1150°C for 60 min decreased with increasing graphite content.
For example, the residual expansion rate of the Fe-8.0%Cu binary system was 2.8%, while it was 1.05% for the specimen with 0.6%C and 0.05% for the specimen with 1.0%C, respectively. Furthermore, shrinkage was observed with the specimens containing more than 1.2%C.
(3) The maximum expansion rate of the Fe-Cu-1.0%C ternary mixed powder compacts increased nearly in proportion to Cu content up to 6.0% but remained constant at higher Cu content.
