Tailoring powder processing and thermal treatment to optimize the densification of W–CuO powder mixtures

Abstract

Abstract W–CuO powder mixtures were prepared by attritor mixing/milling of commercial powders. The reduction steps during heating under He/H 2 gas flow were identified by thermogravimetric analysis (TGA). W–Cu powder mixtures with three different O-content were prepared by adjusting the reduction conditions in a furnace. The effect of O-content on the sintering of powder compacts was then especially investigated. Two sintering steps were identified by dilatometry during liquid phase sintering under He/H 2 atmosphere. The first step was associated to rearrangement after copper melting. The second step was related to the presence of W-oxides at the particle surface: shrinkage was enhanced and the second step was shifted to lower temperatures by using initial powders with low oxygen content, by decreasing the heating rate or by introducing a holding time at 1050 °C. This behaviour was related to a gradual reduction of W-oxides from the edge to the bulk of the samples. Microstructural observations were performed at different stages to confirm the analysis. Powder processing and thermal cycle were optimized to obtain materials with 96–97% relative density.