Effects of tantalum concentration on the microstructures and mechanical properties of tungsten-tantalum alloys

Pure tungsten and tungsten-tantalum alloys with tantalum concentrations of 5, 10, 15 and 20 wt.% were fabricated by spark plasma sintering. Effects of tantalum concentration on the basic characterization of tungsten-tantalum alloys were studied. The results show that the addition of tantalum contributes to a decrease of grain size and an improvement of relative density and mechanical properties. Adding a small amount of tantalum (about 10 wt.%) increases the relative density significantly, while if the concentration of tantalum is higher than 15 wt.%, the relative density decreases apparently. The hardness of the alloy with 10 wt.% tantalum is highest, which is 508.65 HV, 42% higher than pure tungsten. The bending strength of the alloy with 5 wt.% tantalum reaches up to 742 MPa, which is 27.1% higher than pure tungsten. Pure tungsten fractures intergranularly, while the failure mode in the alloy is predominantly transgranular. SEM images show that if the concentration of tantalum is higher than 10 wt.%, tantalum tends to gather together, and this phenomenon has a negative effect on the mechanical property of materials.