Strengthening mechanism and effect of Al2O3 particle on high-temperature tensile properties and microstructure evolution of W–Al2O3 alloys

The W–Al2O3 alloy rods were successfully fabricated by the powder metallurgy process and hot swaging. Subsequently, the high-temperature tensile tests were conducted to characterize the mechanical properties of the W–Al2O3 alloy. At 800 °C, the ultimate tensile strength of W-0.25 wt% Al2O3 alloy is 611.1 MPa, which is 18% higher than that of pure W. After tension, the microstructure evolution was evaluated using metallographic microscope and transmission electron microscopy. For the pure W undergoing deformation at 1000 °C, dynamic recrystallization occurs, leading to the sharp decrease of the strength. However, the microstructure of the W-0.25 wt% Al2O3 alloy contains a large number of sub-grain and low-angle grain boundaries, which does not significantly change in the temperature range of 800–1200 oC, and the work hardening plays a leading role during the high-temperature deformation process. Due to high hardness, the dispersed Al2O3 particles effectively prevent the dislocation movement, displaying a significant strengthening effect.