Mechanical Alloying Effects in Ball-Milled Tungsten-Copper (W-Cu) Composites

摘要

Fine-grained, high-density (97%+ of theoretical density TD), 80 tungsten-20 copper weight-percent (80W-20Cu 58W-42Cu atomic-percent) composites have been prepared using nonconventional alloying techniques. The W and Cu precursor powders were combined by high-energy ball milling in air. A second set of W+Cu mixtures was prepared in hexane to reduce contamination of the powders. The mechanically alloyed W+Cu powder mixtures were then coldpressed into green compacts and sintered at 1,250 deg. C. The effects of varying the milling medium and milling time were examined with density measurements. Longer milling increased product densities with a concomitant order-of-magnitude decrease in grain size; air was found to be a more effective medium than hexane. Residual impurities were identified with energy-dispersive x-ray spectroscopy (EDS), and their effects on sample properties were evaluated with microhardness measurements. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses demonstrated that the as-milled W-Cu alloy structures were metastable, decomposing into the starting W and Cu components upon heating at or above 450 deg. C.