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

Author

Cory C. Sparks, Boise State UniversityFollow

Publication Date

12-2012

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Materials Science and Engineering

Department

Materials Science and Engineering

Supervisory Committee Chair

Darryl P. Butt, Ph.D.

Abstract

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.

Recommended Citation

Sparks, Cory C., "Fabrication of Solid Solution Tungsten-Rhenium Alloys by High Energy Ball Milling and Spark Plasma Sintering" (2012). Boise State University Theses and Dissertations. 328.
https://scholarworks.boisestate.edu/td/328