Effects of Zr addition on the microstructure and mechanical properties of Y-Zr-O complex oxide dispersion-strengthened Mo alloys

Y-Zr-O complex oxide dispersion-strengthened Mo alloys with different Zr contents (Mo-2Y₂O₃–0.6Zr, Mo-1Y₂O₃–0.6Zr, and Mo-1Y₂O₃–1.2Zr, wt%) were designed and fabricated by mechanical alloying and spark plasma sintering to investigate the effect of Zr addition on the microstructure and mechanical properties of this Mo alloy. The size and spatial distribution of oxide particles were characterized using Fresnel contrast mode in TEM, and mechanical properties were measured using small-scale three-point bending tests. Results show that Zr addition leads to the coarsening of oxide particles, especially intergranular particles. Based on Weibull theory, the strength ratio of Mo alloys in three-point bending and tensile tests is well fitted as 1.70. Furthermore, the Mo-2Y₂O₃–0.6Zr alloy exhibits an unprecedented tensile strength and fracture strain of 1059 MPa and 1.01 %, attributed to its ultrafine Mo grains (∼0.3 μm), semi-coherent intragranular oxide nanoprecipitates (∼18.09 nm), and intergranular oxide nanoprecipitates (∼67.11 nm). The theoretical calculation indicates that the strength is mainly affected by grain boundary strengthening and intragranular particle strengthening. The findings can provide a beneficial reference for the relationship between microstructure and mechanical properties of high-performance Mo alloy for nuclear energy applications.