Microstructure, mechanical properties, and strengthening mechanisms of nanostructural Y-Zr-O oxide dispersion-strengthened (ODS) Mo alloys

Nanostructural Y-Zr-O oxide dispersion-strengthened (ODS) Mo alloys were in-situ prepared based on the dissolution and re-precipitation strategy of oxides during mechanical alloying (MA) and spark plasma sintering (SPS). The effect of Zr addition on the microstructures and mechanical properties of Mo-1Y₂O₃-xZr alloy (x = 0.3, 0.6, 0.9, and 1.2 wt%) was investigated. The results show that both intragranular and intergranular Y-Zr-O particles are nanoscale and non-stoichiometric, possessing a different Y/Zr ratio. The Y-Zr-O particles and ultrafine grain structure jointly contribute to high strength (1.87 times over pure Mo) and simultaneously great elongation (2.98 times over pure Mo) of Mo-1Y₂O₃-0.3Zr alloy. The yield strength and elongation are reduced as Zr addition beyond 0.6 wt%, owing to the aggregation of Y-Zr-O particles at grain boundaries. The theoretical calculation indicates that the strength is mainly affected by grain refinement strengthening and Orowan precipitate strengthening. But the strength is less predicted due to a great amount of Y-Zr-O nanoclusters smaller than 5 nm cannot be considered in the statistical analysis by conventional TEM.