Effect of La2O3 content on the densification, microstructure and mechanical property of W-La2O3 alloy via pressureless sintering

Abstract

In the present work, the influences of La2O3 content (0–5.0 wt%) on the densification and grain growth of tungsten (W) nanopowders during pressureless sintering were systematically investigated. The densification inhibitory effect was enhanced with the increase of the amount of La2O3 addition, resulting in that the densification rate decreases from pure W to W/5.0wt%La2O3 composite powder. However, the grain size of W first decreases from 0 wt% to 2.0wt%La2O3 addition due to the increase of number density of La2O3 particles, and then increases from 2.0 wt% to 5.0wt%La2O3 addition because of the significant increase of the particle size and the decrease of the number density. On the premise of achieving near full density, the grain size of all W-La2O3 alloys sintered by pressureless sintering is very small, only 0.47–1.90 μm. The W-2.0wt%La2O3 alloy sintered at 1650 °C with the grain size of 0.47 μm possesses the highest Vickers microhardness of 739.3 HV0.2.