DENSIFICATION AND DILATION OF SINTERED W-CU ALLOYS

This study examines the effect of milling on the densification and dim ensional change of a range of W-Cu alloys. Comilling of tungsten and c opper powders enhance densification as compared to mixing. During heat ing, the compacts prepared from mixed powders swelled between 450 and 600 degrees C. Swelling is detrimental to compact shape retention and restricts densification. Most probably, swelling resulted from reducti on of oxygen impurities in the copper. calculations show that formatio n of reduction products within the powder generates a stress of about 98MPa. This leads to swelling of the copper particles and an overall s welling of the compacts. Compact swelling can be avoided by promoting conditions which prevent stress generation within the compacts, such a s using low oxygen copper powder, pressing the compact at low compacti on pressure, and using an inert sintering atmosphere. Comilling the co nstituents effectively avoids compact swelling. The study suggest alte rnative powders or processing routes to minimize swelling.