Fabrication of Solid Solution Tungsten-Rhenium Alloys by High Energy Ball Milling and Spark Plasma Sintering

摘要

Tungsten-rhenium powders of varying compositions were fabricated by spark plasma sintering (SPS). In initial exploration of the parameter space, W-25 at% Re powders were blended and consolidated by SPS at 1500 to 1900°C with sintering dwell times of 0 to 60 minutes. In addition, the influence of milling was investigated. W-25 at% Re powders were high-energy ball milled at 200 to 400 rpm for 5 hours and consolidated at 1700°C with sintering dwell times of 0 to 60 minutes. The sample densities, grain sizes, porosities, contamination level, and hardness values were measured. The intermetallic content, specifically the fraction of σ-phase, of each sample was determined by scanning electron microscopy (SEM) in the backscatter mode and X-ray diffraction (XRD).Processing parameters were optimized to yield high density and hardness values, with corresponding minimal grain growth, porosity, contamination, and minimal σ-phase content. The optimized process that was developed involved ball milling at 400 rpm for 30 hrs, followed by consolidation at 1800°C and hold times of 30 minutes. This process resulted in a complete solid solution between tungsten and rhenium, and no detectable σ-phase based on TEM/EDS characterization.The optimized ball milling and sintering parameters were extended to W-Re compositions of W-3 at% Re, W-6 at% Re, W-10 at% Re, and these samples were similarly characterized. For each composition, W-Re solid solutions were produced with no detectable σ-phase though the higher rhenium concentrations required longer hold times. Decreasing the rhenium content in the alloys resulted in larger grains, decreased hardness values, higher porosity, and lower densities.