Porous WMoTaNb refractory high entropy alloy fabricated by elemental powder metallurgy

Porous WMoTaNb refractory high-entropy alloys (RHEAs) were successfully fabricated through powder metallurgy using W, Mo, Ta, and Nb elemental powders. The significant disparity in diffusion coefficients among these four elemental powders was strategically exploited to induce the Kirkendall effect during the sintering process, thereby achieving a high porosity ranging from 49.2 % to 57.8 %. Microstructural analysis revealed that the recrystallization behavior during sintering played a crucial role in grain refinement, leading to enhanced strength. Through sintering at 2100 ℃, an equiatomic WMoTaNb refractory high-entropy phase was successfully synthesized in situ. The sequential alloying process of powder particles was determined to follow the order of Nb→Mo→Ta→W. Comparative analysis between samples sintered at 2000 ℃ and 2100 ℃ demonstrated a remarkable 57 % improvement in compressive strength for the latter. This significant enhancement was attributed to the synergistic effects of stronger solution strengthening, more pronounced grain refinement strengthening, and reduced porosity. This study not only validates the feasibility of fabricating porous WMoTaNb RHEAs through elemental powder metallurgy but also provides valuable insights for the advancement of porous RHEAs. The findings contribute to the understanding of microstructure-property relationships in these materials and offer potential guidance for optimizing processing parameters in future research and development of porous RHEAs.