W-Y2O3 composites obtained by mechanical alloying and sintering

Abstract

The aim of this work was to manufacture tungsten composites from different initial powder mixtures by mechanical alloying followed by sintering. Two initial powder mixtures, W + 5 wt% of Y2O3 and W + 10 wt% of Y2O3, and pure W for comparison were mechanically alloyed for 50 h in a Fritsch Pulverisette P5 planetary ball mill under an argon atmosphere. The final products were consolidated by pulse plasma sintering at 1640 °C under a pressure of 20 MPa. The powders and consolidated pellets were examined by the XRD method. The obtained results show that during milling, the tungsten based solid solution formed. After consolidation, the XRD examination revealed that in addition to the tungsten-based solid solution and yttria, new carbide phases (Fe3C, WC, W2C and Fe3W3C) appeared. The graphite present in the carbides originated from the die used in the sintering process. SEM observations of the surfaces of the sinters revealed that the microstructure is not homogeneous and consists of areas rich in one or two elements, such as W, C, Fe or the Y2O3 phase. The microhardness of the pellets increases with the increasing content of the Y2O3 strengthening phase, whereas the values of the relative density decrease.