抄録
The influence of graphite addition on the dimensional change and the strength was studied in some sintered mixed elemental alloys, i.e. Fe-Cu-C alloys (Cu; 3%, C; 0-0.9%) and Fe-Cu-P-C alloys (Cu; 3%, P; 0.28%, C; 0-0.9%) and then the effect of phosphorus addition on the sintered Fe-Cu-C alloys was discussed. The phosphorus addition was done by using a Cu-8.4%P eutectic alloy powder.
The results obtained are as follows;
1) In the sintered Fe-Cu-C alloys, the growth of the compacts decreased with increasing graphite content, in contrast, in Fe-Cu-P-C sintered alloys, the dimensional change of the compacts was almost constant with graphite content.
2) With the addition of graphite in the Fe-Cu mixed powder compacts, penetration of the liquid copper into the boundaries of the iron powder particles was reduced, so that copper segregation in the alloy structure was noted particularly for the sintered high carbon Fe-Cu-C alloys. This appears to be attributed the decreasing of the wettability of the liquid copper to the solid iron with increasing the graphite content. In comparison, the sintered Fe-Cu-P-C alloys exhibited the great copper segregation in the alloy structure especially at lower carbon level alloys and this may be attributable to the early stabilization of a-Fe phase with phosphorus and smaller copper solubility in the phase. But high addition of graphite enhances the stability of γ-Fe and allows a more rapid diffusion of copper into the γ-Fe, so that the copper homogeneity in the alloy structure was obtained.
3) The tensile strength of sintered Fe-Cu-P-C alloys was superior to sintered Fe-Cu-C alloys in the range of 0-0.9% graphite content. Additionally the toughness of the Fe-Cu-P-C alloys was extremely high at graphite addition levels below about 0.4%.
