Mechanical properties and strengthening mechanism of the hydrothermal synthesis of nano-sized α-Al2O3 ceramic particle reinforced molybdenum alloy

Nano-sized α-Al2O3 ceramic-particle-reinforced molybdenum alloy plates were fabricated by a series of processes including hydrothermal synthesis, powder metallurgy, and rolling. The quantitative effect of α-Al2O3 ceramic (particle size and volume fraction) on the microstructures and mechanical properties of molybdenum alloy plates was investigated. Nano-sized α-Al2O3 ceramic particles were obtained and uniformly dispersed in the molybdenum matrix. The α-Al2O3 ceramic refined the molybdenum grains and remarkably increased the microhardness, elastic modulus, and yield strength. The yield strength of the alloy reached a peak value when the α-Al2O3 ceramic content was 1.28 vol% and increased by 61.07%–90.2% compared with that of pure molybdenum after annealing at 1000 °C-1300 °C. A quantitative yield strength model correlating α-Al2O3 particle size, α-Al2O3 volume fraction, molybdenum grain size, and annealing temperature was built. This model attributes the strengthening of alloy to the synergy effects of grain refinement strengthening (σHP) and Orowan strengthening (σp). The addition of fine α-Al2O3 ceramic resulted in Orowan strengthening and fine molybdenum grains, thereby increasing yield strength of alloy.