Fabrication of high temperature oxides dispersion strengthened tungsten composites by spark plasma sintering process

The paper describes the fabrication process of high temperature oxides, such as Y2O3, HfO2 and La2O3, dispersed tungsten composites by spark plasma sintering. The oxide contents varied from 0 to 5 wt% and sintering was conducted for 3 min at 1700 °C. Among three kinds of oxides, Y2O3 is the most efficient element to consolidate W powder. As dispersed up to 5 wt% Y2O3 into the matrix, the relative density of the W composite is increased up to nearly 100% of theoretical value. In order to analyze the effect of Y2O3 particles on the densification of W powders, the microstructure of W–Y2O3 composite is observed using the transmission electron microscopy. By this experiment, it is found that dark phases, which had been known as Y2O3 phase, are composed of W, Y and O. Therefore, during sintering, W atoms move through Y2O3 phases as well as W grain boundaries, thereby W and Y2O3 are soluble, and so sinterability of W is enhanced. The hardness of the composite is increased from 350 to 510 kg/mm2 with increasing Y2O3 contents since the relative density is increased and the grain size is reduced from 20 to 4 μm. However, in case of HfO2 and La2O3, the hardness of the composites is decreased even though the grain size is reduced because of their lower relative densities.