Longitudinal and shear wave velocities in pure tungsten and tungsten fiber-reinforced tungsten composites

Longitudinal and shear wave velocities in pure tungsten and tungsten fiber-reinforced tungsten (W_f/W) composites were studied by laser ultrasonic measurements. The samples were produced from powders or powder/fiber mixtures by spark plasma sintering process. It was found that sintering temperature, as a processing parameter, has the largest effect. Higher sintering temperatures result in faster wave velocities. For example, longitudinal wave velocities and their standard deviations in sintered W at 1800 °C and 2000 °C were 4834 ± 53 m s⁻¹ and 5043 ± 47 m s⁻¹. In comparison, the average longitudinal wave velocity for a polycrystalline reference W was 5227 ± 5 m s⁻¹. The values for W_f/W composites fall between the two sintered samples. However, the thicker Yttria (Y₂O₃) fiber/matrix interface resulted in faster wave velocities. The elastic moduli were calculated from the sound velocities using average density measurements. The standard relations for isotropic, homogeneous material were used. It was found that the shear, bulk, Young's modulus are 80%-90% of the values for polycrystalline tungsten, while the temperature dependency from 25 °C to 450 °C is similar.