Microstructure refinement in W–Y2O3 alloys via an improved hydrothermal synthesis method and low temperature sintering
In order to prepare high performance oxide-dispersion-strengthened tungsten-based alloys, W–Y2O3 composite nanopowders were prepared using an improved hydrothermal synthesis method with the addition of the surfactant polyvinyl pyrrolidone (PVP). The resulting hydrothermally synthesized blue (NH4)XWO3 compound is an excellent tungsten source to use to prepare ultrafine W–Y2O3 composite nanopowders with an average W grain size of only 15 nm. Then, low temperature sintering characteristics showed that the sintered W–Y2O3 alloys prepared using the hydrothermally synthesized blue (NH4)XWO3 complex as the tungsten source possess refined W grains of about 200 nm, a relatively high density of 97.8%, well-dispersed Y2O3 particles (<150 nm), and thus a high hardness value of 732.6 ± 37.0 HV0.2. It is worth noting that the alloys maintain a relatively high density as well as a fine grain size. Based on our results, the improved hydrothermal synthesis method with surfactant addition is a promising way by which to fabricate high performance oxide-dispersion-strengthened tungsten-based alloys with ultrafine grains.