Microstructural Evolution and Mechanical Properties of Spark Plasma Sintering of Tantalum-Tungsten Alloy

Due to the rapid sintering and densification, spark plasma sintering (SPS) technology can significantly inhibit grain coarsening, and obtain alloy with high density and uniform microstructure. Tantalum-tungsten (Ta-W) alloy had been fabricated by powder metallurgy and consolidated by SPS at temperature of 1600 degrees C for 5 min at the pressure of 35 MPa. Specimens of pure Ta and four tantalum-based alloys with different concentrations of tungsten ranging from 2.5 to 10 were used to investigate the behavior of developed alloys. X-ray diffraction analyses were applied for all compositions of Ta-W alloys. The morphology of fracture sections was analyzed by scanning electron microscopy (SEM). Morphologies of initial Ta and W powders, microstructures of sintering Ta-W alloy and tensile fractographs of the specimens with different components were observed. When the concentrations of tungsten were distributed with 2.5 wt%, 5 wt%, 7.5 wt% and 10 wt%, the measured densities were 16.151 g/cm(3), 15.756 g/cm(3), 15.711 g/cm(3), 15.665 g/cm(3) and 15.670 g/cm(3) respectively. As the content of tungsten increased, the density of the alloy decreased and the grain was refined, meanwhile the micro-hardness of the samples increased gradually. Furthermore, the addition of tungsten could greatly enhance the strength of the alloys, but decrease the plasticity of the alloys. Ta-2.5 wt%W shows the maximum bending strength with a value of 832.29 MPa, while the percentage of transgranular fracture increased with the increase of tungsten content.