Preparation of intragranular-oxide-strengthened ultrafine-grained tungsten via low-temperature pressureless sintering

In conventional powder metallurgy, tungsten (W) sintering is commonly carried out at over 2000 degrees C, which inevitably causes undesired grain growth and degraded strength. To address this issue, we introduced a feasible and scalable method to prepare dense and strong W alloys. The process route involved a wet-chemical technique (solution combustion synthesis), by which, uniformly blended W/La2O3 composite powder with a particle diameter of approximately 36 nm was obtained. Subsequently, with the advantage of the high activity of the as-synthesized composite powder, we successfully prepared W-La2O3 alloy with a relative density of 95.0% using pressureless sintering at a temperature as low as 1500 degrees C. Owing to the low sintering temperature and the pinning effect of the in situ-generated oxide particles on the grain boundaries, the alloy could achieve a grain size of 0.57 mu m. With the grain boundary and intragranular-oxide strengthening, the microhardness and compressive strength reached 684.0 HV0.2 and 2119 MPa, respectively, which are comparable to or even higher than those reported in the literature.