Properties of Y₂O₃ Dispersion Strengthened W Fabricated by Ultrasonic Spray Pyrolysis and Pressure Sintering

The effects of fabrication method on the microstructure and sinterability of W-1 wt% Y₂O₃ were analyzed. W composite powders dispersed with Y₂O₃ particles were synthesized by the ultrasonic spray pyrolysis process or the ultrasonic spray pyrolysis/polymer solution process. A dense composite was fabricated by a combination of spark plasma sintering and final hot isostatic pressing. The powder synthesized by the ultrasonic spray pyrolysis had fine dispersed particles on the surface of the cubic powder and was composed of W, Y₂O₃ and W-oxides. On the other hand, in the case of the ultrasonic spray pyrolysis/polymer solution process, the nano-sized particles formed agglomerates and existed only as pure W and Y₂O₃ phases. All the sintered compacts treated with HIP showed an increase in relative density, and the sintered compacts of the powder synthesized by the ultrasonic spray pyrolysis/polymer solution process showed a maximum relative density of 97~99% and a fine grain size. The change in microstructure with different powder processing was explained by the presence of W-oxide and the size and distribution of Y₂O₃ particles. The Vickers hardness of the sintered compact reached the largest value of about 5 GPa in the powder synthesized by the ultrasonic spray pyrolysis/polymer solution process, which was interpreted to be a result of the relatively high density and decreased grain size.