Ultra-fine W–Y2O3 composite powders prepared by an improved chemical co-precipitation method and its interface structure after spark plasma sintering

Abstract

Y2O3-doped tungsten (W–Y2O3) composite powders prepared by a traditional chemical co-precipitation method possess obvious bimodal distribution in size, which would deteriorate their sintering properties. The bimodal distribution can be effectively eliminated by an improved chemical co-precipitation method, in which the cationic surfactant cetyltrimethylammonium bromide (CTAB) was innovatively employed. The reduced powders with excellent uniformity have an average grain size of only ~ 31.5 nm. It is noteworthy that Y2O3 particles would fuse and grow with the growth of W grains during subsequent spark plasma sintering (SPS) process, which was rarely reported in relevant literature before. On top of that, phase interfaces of sintered W–Y2O3 alloys were systematically analyzed. Compared to the intracrystalline oxygen content, the oxygen content at W/Y2O3 phase boundaries is relatively higher. It can be found that the (110) crystal planes of W form coherent, semi-coherent, and non-coherent interfaces with different crystal planes of Y2O3. The weak interfacial bonding strength between W and Y2O3 phases results from relatively more oxygen impurities as well as more semi-coherent/non-coherent interfaces at phase boundaries compared with the inner W grains.