Effect of La2O3 addition on preparation of ultrafine tungsten powder and its sintering densification behavior

Tungsten and its alloys occupy a critical position in modern defense, nuclear energy, vacuum electronics, and lighting applications due to their unique and irreplaceable properties. However, the intrinsic brittleness, thermal shock brittleness, and recrystallization brittleness of tungsten significantly limit its application and development. To address the high brittleness and poor strength-toughness of tungsten, the present work aimed to first prepare La 2 O 3 dispersion-strengthened composite powders by spray drying‑hydrogen reduction process. Subsequently, highly dense ultrafine-grained dispersion-strengthened W alloys were fabricated via spark plasma sintering (SPS). It was indicated that La 2 O 3 exhibited a significant refining effect on the powder; however, excessive La 2 O 3 addition led to aggregation, promoting the chemical vapor transport (CVT) mechanism and ultimately causing powder coarsening. During the sintering process, the uneven distribution and aggregation of secondary phase particles diminished their grain refinement capability. The resulting nanostructured W-0.5La 2 O 3 (wt%) composite powder exhibited a grain size of 109 nm, while the W-0.5La 2 O 3 alloy possessed the highest Vickers hardness of 647.9 HV 0.2 . Furthermore, the reduction and densification mechanisms of composite powder were investigated in detail.