A REVIEW OF THE EFFECTS OF STARTING MATERIAL ON THE PROCESSING AND PROPERTIES OF TUNGSTEN, MOLYBDENUM, COLUMBIUM, AND TANTALUM

摘要

Commercial powders of tungsten, molybdenum, columbium, and tantalum are generally produced in high purity (99.9+, 99.9+, 99.5+,' 99.5+ per cent, respectively) with particle sizes ranging from 0.1 to about 350 microns. The major impurities in these metals and their alloys are interstitials (carbon, oxygen, nitrogen, and hydrogen), which make up about half the total impurity content. These impurities are largely removed by consolidation via powder metallurgy, arc melting, or electron-beam refining, with the latter being the most effective. The remainder of the impurities are usually substitutional metallics. To some extent, consolidation removes these impurities as well, especially the volatile ones.nIn the case of tungsten, the starting powder can have a significant effect on the properties of sheet or other shapes in spite of purification during consolidation.