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

摘要

In conventional powder metallurgy, tungsten (W) sintering is commonly carried out at over 2000 ℃, 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/La_2O_3 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-La_2O_3 alloy with a relative density of 95.0% using pressureless sintering at a temperature as low as 1500 ℃. 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 μm. With the grain boundary and intragranular-oxide strengthening, the microhardness and compressive strength reached 684.0 HV_(0.2) and 2119 MPa, respectively, which are comparable to or even higher than those reported in the literature.