Microstructure evolution and strengthening mechanism of boron doped molybdenum alloy solid solution rolled plates

Molybdenum alloy plates were prepared via powder metallurgy and the rolling process, and their microstructure and mechanical properties at room temperature were characterized. The results indicate that the grain size of the molybdenum alloy is significantly refined as the boron content increases. The Mo-1.0B alloy exhibited substantial grain refinement, with an average grain size of 7.12 μm representing a 42.6% reduction compared to 12.41 μm of undoped molybdenum. Microstructure and EBSD analyses demonstrate that boron doping effectively inhibited the recrystallization process in the Mo alloy. Notably, compared to previously studied molybdenum alloys, the newly developed alloys exhibit an unprecedented breakthrough in both strength and plasticity: the ultimate tensile strength of the rolled Mo-1.0B alloy plate reaches 1016.6   MPa, with a total elongation of 8.6%, significantly surpassing that of the 916.3   MPa and 6.5% of pure molybdenum. After annealing at 1200 ℃, the ultimate tensile strength of the rolled Mo-1.0B alloy plate reaches 532.5   MPa, with a total elongation of 67.4%, markedly higher than that of the 505.3   MPa and 46.9% of pure molybdenum. The excellent mechanical properties are primarily attributed to solid solution strengthening, dislocation strengthening, and grain boundary strengthening of Mo-B. Additionally, a quantitative strengthening model correlating strength, dislocation density, solid solution strengthening, and grain size was established, clarifying the strengthening mechanism.