Fabrication of Mo-Y2O3 alloys using hydrothermal synthesis and spark plasma sintering

Fine-grained Mo alloys doped with uniformly distributed nanoscale Y2O3 particles were successfully prepared by employing two powerful strategies: fabricating high-quality precursor powders using hydrothermal synthesis and subsequent powder consolidation by spark plasma sintering (SPS) technique. In this study, the effect of hydrothermal variables on the morphology and existent form of yttrium and Mo was systematically studied, and the refinement mechanism of reduced mixing powders and the densification under the different sintering parameters were investigated. The results show that spherical Y2(CO3)3·2H2O gradually replaced Y(OH)CO3 owing to the increased concentration of hydrogen bonds and CO32− at excess alcohol and urea, and lamellar (NH4)2Mo4O13 developed into large pillar-shaped h-MoO3 with decreasing pH. Due to the low calculated lattice mismatch degree of Mo/Y2O3 interfaces ~10.9%, Y2O3 particles further refined and homogenized the reduced mixing powders as heterogeneous nucleating sites. After sintering at 1700 °C for 5 min with a heating rate of 100 °C/min, Mo-Y2O3 alloys possessed fine grains of 1.80 ± 0.17 μm, a high density of 98.18% and the high indentation hardness of 314.77 ± 26.12 HV0.3 and 4.82 ± 0.53 GPa HIT. The Y2O3 particles were uniformly distributed in the Mo matrix, and semi-coherent with Mo lattice, with the orientation relationships as follows: (010)Y2O3//(011)Mo, (01-1)Y2O3//(020)Mo, and [100]Y2O3//[100]Mo.