1989 Volume 53 Issue 2 Pages 221-226
The lowest sintering temperature (Tsc) for complete densification of Fe, Co, Ni and Cu ultrafine metal powders (average particle size, 0.02-0.05 μm; oxygen content, 6-15 mass%) was investigated under the pressure up to 400 MPa in H2 gas, and the crystal grain size and hardness of the dense sintered compacts were measured.
Under 400 MPa, Tsc for Fe, Co, Ni and Cu powders were about 620, 670, 470 and 470 K, respectively, which were 350∼600 K lower than those under 0 MPa. The minimum average crystal grain sizes of Fe, Co, Ni and Cu dense sintered compacts were as small as about 0.08, 0.21, 0.12 and 0.40 μm, respectively. The highest values of hardness (HV) of the sintered compacts were abut 600, 550, 550 and 130, which were extremely high compared with usual coarsegrained metals. The Hall-petch linear relationship between HV and the inverse of square root of grain size hold for each element.
