Abstract:A comparative study was conducted by using solution combustion synthesis with three different doping routes (liquid-liquid (WL10), liquid-solid (WLNO) and solid-solid (WLO)) to produce nanoscale powders and further fabricate the ultrafine-grained W-1.0wt.%La₂O₃ alloys by pressureless sintering. Compared with pure tungsten, W-1.0wt.%La₂O₃ alloys exhibit ultrafine grains and excellent mechanical properties. After sintering, the average grain size of the WLO sample is larger than that of WL10 and WLNO samples; the microhardness values of WL10 and WLNO samples are similar but larger than the value of WLO sample. The optimized La₂O₃ particles are obtained in the WL10 sample after sintering at 1500 °C with the minimum mean size by comparing with WLNO and WLO samples, which are uniformly distributed either at grain boundaries or in the grain interior with the sizes of (57±29.7) and (27±13.1) nm, respectively. This study exhibits ultrafine microstructure and outperforming mechanical properties of the W-1.0wt.%La₂O₃ alloy via the liquid-liquid doping route, as compared with conventionally-manufactured tungsten materials.

Key words: tungsten alloy; solution combustion synthesis; doping route; ultrafine grain; microhardness