A Comparative Assessment of Explosive and Other Methods of Compaction in the Production of Tungsten—Copper Composites

Abstract

In the production of tungsten-copper composites by pressing and sintering mixed powders followed by hot working, or by liquid-phase infiltration techniques, difficulties arise in obtaining a fully dense material, particularly at tungsten contents > 70 wt.-%. W–Cu composites containing between 70 and 90 wt.-% W have been made by various routes including liquid-phase sintering, hot forging, triaxial compaction, isostatic re-pressing, and explosive compaction, and a comparative assessment of their mechanical and electrical properties has been made. In the case of composites containing 70 wt.-% W, it has been shown that the maximum density achieved by liquid-phase sintering at up to 1753 K increases as the Cu particle size decreases. A density of 95·5% theoretical was obtained using −350 mesh Cu powder. Isostatic repressing at 1·4 GPa of liquid-phase sintered composites yielded a maximum density of 95·5% theoretical, irrespective of initial Cu particle size. Triaxial compaction of the mixed powders was found to be unsuitable in that fracturing of the compact was observed. Hot forging of sintered compacts at up to 1173 K yielded a product of 99% theoretical density (T.D.) in the 70/30 composition, whereas when the W content was raised to 80 wt.-%, a maximum density of 90% T.D. was attained, with fracturing of the composite. The use of the direct explosive-compaction technique has enabled composites with up to 90 wt.-% W to be compacted to 97·8% T.D. In general, the hardness of the composites increased with increasing final density, although explosively compacted composites had higher hardness values than hot-forged composites of similar density. The electrical conductivity for a given composition was fairly constant irrespective of method of production, provided that an annealing treatment was given after re-pressing or explosive compacting.