Effects of milling time and sintering temperature on structural evolution, densification behavior and properties of a W-20wt.%Cu alloy

The dependence of structural evolution, densification behavior and property changes of a W-20wt.%Cu alloy powder on milling time and sintering temperature were investigated in this study. With the milling time being less than 48 h, the average size, morphology and microstructure of the milled powder particles are strongly influenced by the milling time. But with increasing the milling time from 48 to 96 h, no clear changes are observed other than a distinct decrease in the W lattice parameter. The 48 h milled nanocrystalline alloy powder was chosen to fabricate bulk W-20wt.%Cu samples by vacuum sintering for 2 h at 1050, 1150 and 1250 °C respectively. During sintering at 1150 °C, both the powder particles and W particles in the powder particles undergo rearrangement, making the sample sintered at 1150 °C have the highest relative density, hardness and electrical and thermal conductivities. Due to insufficient solid state diffusion and the formation of large W contiguities as well as Cu pools, the samples sintered at 1050 and 1250 °C, respectively, have lower relative densities in comparison with the sample sintered at 1150 °C. The impurity introduced to the powder particles during milling also affects the densification of the powder compacts and their physical properties.