Abstract
The effects of the additions of a small amount (4 mass%) of Al, Cr and Si on the densification behavior of Cu fine powder of 5 μm, which is usuable for metal injection molding (MIM), were investigated in relation to the relative density of green compact (Dg≅52 and 92%) and sintering atmosphere (H2 and vacuum).
The results obtained were as follows: (1) In H2 gas sintering, Cu-Al, -Cr and -Si compacts did not densified to full density in the same way as Cu compact for Dg≅52%. For Dg≅92%, however, Cu-Al and -Cr compacts completely densified. (2) In vacuum sintering, Cu-Al, -Cr and -Si compacts also did not completely densified for Dg≅52%, differing from Cu compact. For Dg≅92%, the results were nearly the same as those in H2 sintering. The Cu-Si compact did not completely densified in any case, or even expanded. (3) These results could be explained mainly by the equlibrium gas pressure ratio of H2O/H2 in the reduction reaction of the oxide with H2 gas, the sinterability of the oxides of added elements, adsorbed H2O gas, etc.
