Preparation of ultra-fine grain W-Y2O3 alloy by an improved wet chemical method and two-step spark plasma sintering

The Y2O3 doped tungsten composite powder was synthesized via an improved chemical method where the polymeric surfactant Polyvinyl Pyrrolidone (PVP, K17) addition and ultrasonic treatment were both innovatively employed. Consequently, the average tungsten grain size of 10.7 nm was obtained for the composite powder precursor. To suppress the grain growth, two-step spark plasma sintering (SPS) was employed for the consolidation of powder precursor. It was found that in the sintered W-Y2O3 alloys, nano (2-10 nm) and submicron (100-300 nm) oxide particles were uniformly dispersed within tungsten grains and at tungsten grain boundaries, respectively. The average tungsten grain size of W-Y2O3 alloys whose final sintering temperature are 1400 and 1600 degrees C are 450 and 550 nm, respectively. Both of them are much smaller than that reported in previous studies. Their corresponding Vickers micro-hardness is 543.2 and 729.1 Hv, respectively, also better than the values obtained in previous works. These results indicate that the improved wet chemical method combined with ultrasonic treatment and PVP addition developed in our work is a promising way to fabricate high performance oxide-dispersion-strengthened tungsten based alloys with ultra-fine grain. (C) 2016 Elsevier B.V. All rights reserved.