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

Abstract

The paper describes the fabrication process of high temperature oxides, such as Y(2)O(3), HfO(2) and La(2)O(3), 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 degrees C. Among three kinds of oxides, Y(2)O(3) is the most efficient element to consolidate W powder. As dispersed up to 5 wt% Y(2)O(3) 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 Y(2)O(3) particles on the densification of W powders, the microstructure Of W-Y(2)O(3) composite is observed using the transmission electron microscopy. By this experiment, it is found that dark phases, which had been known as Y(2)O(3) phase, are composed of W, Y and O. Therefore, during sintering, W atoms move through Y(2)O(3) phases as well as W grain boundaries, thereby W and Y(2)O(3) are soluble, and so sinterability of W is enhanced. The hardness of the composite is increased from 350 to 510 kg/mm(2) with increasing Y(2)O(3) contents since the relative density is increased and the grain size is reduced from 20 to 4 pm. However, in case of HfO(2) and La(2)O(3), the hardness of the composites is decreased even though the grain size is reduced because of their lower relative densities. (C) 2009 Elsevier Ltd. All rights reserved.