Effect mechanism of oxide doping on the microstructure and mechanical properties of Mo-Y2O3 alloys

It is an effective way to enhance the mechanical properties of Mo alloy by adding oxide strengthening phase. However, the oxide second-phase particles in oxide dispersion strengthened Mo (ODS-Mo) alloy prepared via traditional mechanical alloying generally coarsen at grain boundaries (GBs), greatly weakening their strengthening effect. To solve this problem, single and multiple oxide particles strengthened Mo alloys are developed via wet chemical method and subsequent low-temperature sintering in this work. After doping CeO2, the compressive yield strength (340.3 +/- 8.1 MPa) and hardness (410 +/- 13 HV) of Mo-Y2O3 (Mo-Y) alloy were decreased by 17.9% and 22.7%, respectively. However, after doping La2O3, the compressive yield strength and hardness of Mo-Y alloy are further increased by 89.4% and 21.0%, respectively. According to microstructure observation and theoretical calculation, CeO2 doping decreases the volume fraction of intergranular oxide particles and weakens interfacial drag force, finally promoting Mo grain growth and worsening the mechanical properties of Mo-Y alloy. In contrast, after doping La2O3, more oxide particles are dispersed at GBs, and their coarsening are inhibited. This results in a stronger Zener force. Moreover, interfacial drag force can also be increased through doping La2O3. Two forces synergistically hinder GBs migration. Therefore, La2O3 doping leads to Mo grain refinement and ultimately enhances the mechanical properties of Mo-Y alloy. These results in our work can provide theoretical guidance for choosing proper oxide dopants to prepare ODS alloys with excellent mechanical properties.