Effect of Y2O3 nanoparticles on enhancing microstructure and mechanical properties of oxide dispersion strengthened W alloy

Abstract

Dispersion of oxide nanoparticles in W, leading to the dispersion strengthening of W alloys, has emerged as a viable strategy to overcome the brittleness of W. In particular, the introduction of stable Y2O3 as a secondary phase refines the grain and enhances the densification of W, leading to an increase in the density of sintered alloy. Thus, analyzing the composite effects of Y2O3 on the alloy, which has homogeneous dispersion of Y2O3 nanoparticles, can allow enhanced mechanical properties of the W-Y2O3 alloy. However, to date, most studies have focused on synthesis methodology for nanocomposites, which is advantageous to grain refinement and dispersion. It is worth paying attention to the interaction in the W-Y2O3 system, such as the ternary oxide system (W-Y-O) with a low eutectic temperature and the possibility of liquid-phase sintering, which has been reported a few. In this study, the effect of Y2O3 nanoparticles on the microstructure and micro-Vickers hardness of W was experimentally evaluated. W-Y2O3 alloys with precisely controlled compositions from 1 wt% to 10 wt%Y2O3 were successfully fabricated using an ultrasonic spray pyrolysis process and a subsequent spark plasma sintering. The proposed process yielded Y2O3 nanoparticles with uniform dimensions and distributions even after sintering. Furthermore, the formation of Y2WO6 and a liquid-phase sintered structure, as products of the interaction between W and Y2O3 depending on the Y2O3 fraction, were observed, and thermodynamical formation routes were suggested. Evidently, the W-2wt%Y2O3 sintered alloy, with uniformly dispersed Y2O3 nanoparticles (<50 nm), exhibited an improved hardness of 7.21 ± 0.15 GPa, as the W grains were refined to approximately 760 nm, and their density increased to 96.48%.