Effect of Hf content on microstructure and properties of ultrafine W-Y2O3 composites prepared by wet chemical method

In this paper, based on existing W-Y2O3 materials, trace amounts of Hf4+ were introduced into Y2O3 to regulate the interface between the second phase yttrium oxide and tungsten grains, and thus improving the overall performance of tungsten-based materials. By adjusting the doping ratio of Y to Hf elements, nanoscale tungsten-based composite powders were obtained and W-Y2(Hf)O3 composites were prepared by conventional sintering with hydrogen. The W-Y2(Hf)O3 composites were characterized and analyzed by SEM and TEM to study the action law of Y and Hf elements in the material. The results show that the doping of Hf elements is beneficial to the subsequent hydrogen reduction. Under the condition of constant second phase doping, when the Hf content increases, the particle size of the obtained powder decreases, and the particle size of W-3Y-7Hf is about 100nm, which is obviously smaller than the traditional prepared W-Y2O3 powder. After sintering, the grain size of the sintered block is refined, and the microhardness and relative density increase. The sintered block with W-3Y-7Hf has the highest microhardness, which is 513.7HV0.2, and the density is 97.6%. The addition of both Y and Hf elements to the tungsten-based material results in the formation of composite second-phase oxide Y2Hf2O7 particles at the grain boundaries and intra-grain of the tungsten grains, which are smaller in size and have a stronger dispersion strengthening effect. The particle size of the second phase oxide in W-3Y-7Hf is only about 200 nm, which has a good interfacial bonding relationship with tungsten grain boundaries and forms a semi-coherent interface. © 2024 Central South University of Technology. All rights reserved.