Microstructure evolution and strengthening mechanism of rolled Mo-ZrO2 alloy plates after high temperature annealing

Molybdenum alloy plates with different ZrO ₂ volume contents were prepared by liquid-liquid doping. The microstructures were characterized by scanning electron microscope and transmission electron microscope. The mechanical properties of the alloy were tested by microhardness tester and a precision universal testing machine. The addition of sub-micron ZrO ₂ can significantly reduce the grain size of Mo alloys. For the rolled Mo-0.4% ZrO ₂ alloy plate, the grain size is 5.8 μm in comparison with 11.2 μm of pure Mo. After vacuum annealing at 1200 °C, the grain size of Mo-0.4% ZrO ₂ alloy has not obvious change although pure Mo grain size is sharply increased to 30.3 μm. The addition of ZrO ₂ can increase the recrystallization temperature and improve mechanical properties of Mo alloy. The recrystallization temperature of Mo-0.4% ZrO ₂ is increased by 200–300 °C as analyzed by microscopic morphology and EBSD results. The elongation of Mo-0.4% ZrO ₂ annealed at 1200 °C reached 49% and the strength remained at 482 MPa, which were 120% and 35 MPa higher than that of pure Mo, respectively. The addition of ZrO ₂ can change the slip system of Mo alloy from {110}〈111〉 to {123} 〈111〉, which increases the number of slip systems in the Mo alloy and thus increases the elongation of the Mo alloy. The strengthening model was built and strengthening mechanism clarified.