Microstructure and sintering behavior of W-Cu nanocomposite powder produced by thermo-chemical process

Abstract

The microstructure and sintering behavior of W-20wt.%Cu nanocomposite powder produced by a thermo-chemical process were investigated in terms of the effects of residual oxide and heat treatment on liquid phase sintering. Spray dried oxide powder showed spherical agglomerate with a hollow structure and a different Cu phase distribution with regard to position. The hydrogen reduced W Cu nanocomposite powder consisted of W-Cu agglomerate particles less than 200 nm and also contained small amount Of WO2 phase. The presence of small amount of W residual oxide yielded a relatively low sintered density of 90% theoretical density (TD) after sintering at 1200 degreesC. However, the heat treatment at 700 degreesC before sintering process raised the sintered density up to 94%TD. This is attributed to removal of residual oxide during the heat treatment. With increasing the heat treatment temperature, however, the sintered density was decreased, simultaneously yielding an anisotropic shrinkage behavior. Such an unfavorable sintering property is presumably ascribed by local densification process which leads to formation of strong W skeleton in the compact. (C) 2002 Elsevier Science Ltd. All rights reserved.