Hiroyasu Mitani1, Yuko Hanatate2 and Kazuhiko Majima1
1Department of Materials Science, Faculty of Engineering, Osaka University, Suita
It is known that the Fe-Ni binary mixed powder compacts well contracts during the sintering process, in which case only the Fe powder of coarse particle size such as electrolytic Fe or reduced Fe powder and carbonyl Ni powder of fine particle size have been used.
However the effect of particle size on the sintering behavior has not been considered. Therefore, in this work, by use of Fe and Ni powders of coarse and fine particle sizes, dimensional changes during sintering were investigated mainly through the differential dilatometer.
The results obtained are summarized as follows. During sintering, expansion was observed in the Fe-Ni mixed powder compacts, of the same grain size. In the case of the Fe-Ni compacts composed of coarse Fe powder and fine Ni powder, sintering was remarkably accelerated. Similar phenomena were observed in the case of the sintering of the coarse Fe-fine Fe powder compacts. These results suggested that the shrinkage due to the sintering of the fine powders played an important role in the acceleration of sintering. However, the amount of shrinkage for the former was larger than that for the latter. Therefore in addition to the fine powder effect, the essential mechanism of the accelerated sintering due to Ni additions must be considered, as shown in the sintering of the coarse Fe-coarse Ni mixed powder compacts containing up to 2 wt%Ni.
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