Effects of pressure parameters on alumina made by powder injection moulding

The effects of injection molding pressure and holding time on the propertie s of injection moulded (IM) parts, and the pressure-volume-temperature (PVT ) relationship of the plastic ingredient and alumina feedstocks were invest igated. The properties of IM parts include the mass, dimension, surface fla tness, green density, sintered density and four-point bending fracture stre ngth of the test bars. The results reveal that the pressure-time traces whe re the gate pressure is increased from 22 to 117 MPa and the holding time u p to 75 s, illustrate the trend of the property change under these pressure s. High holding pressures (greater than or equal to 70 MPa) and longer hold ing time (more than 5 s) would be favored to increase molded mass, dimensio n and to decrease the surface sinking of green pieces. The data also show t hat the pressures and holding time exert no significant influence on the bu lk density of green parts, the sintered density nor the bending strength of sintered alumina. (C) 2000 Elsevier Science Ltd. All rights reserved.