Spark plasma sintering of Mo–W powders prepared by mechanical alloying

Mo–W alloys of varying composition were successfully produced by spark plasma sintering at two sintering temperatures. The formation of solid solutions was detected by XRD measurements and microscopic observation. After sintering, all specimens show polycrystalline single-phase microstructure. The measured lattice parameters are in accordance with the theoretical values calculated by Vegard’s rule. Relative densities higher than 96% were achieved. A precondition for the formation of solid solutions is the application of mechanical alloyed Mo–W powders prepared by high-energy ball milling. The milling induces high defect densities inside the particles, which supports the interdiffusion of both elements during sintering.The tungsten content influences the grain size and the microhardness of the specimens. With increasing tungsten content, the grain size decreases strongly, whereas the microhardness increases. The microhardness of the sintered alloys is larger than that expected from solid-solution strengthening. This effect is the consequence of the strong strain hardening of powder particles during high-energy milling. The strain hardening of powder particles is not completely reduced by the short sintering process.

► Mo–W alloys of varying composition can be successfully produced by SPS. ► Relative densities higher than 96% are achieved. ► The sintering process is supported by the mechanical alloying of the powders. ► The grain size of the alloys decreases with the increase of tungsten content. ► The microhardness is influenced by solid solution strengthening and by strain hardening.