Yield strength of molybdenum, tantalum and tungsten at high strain rates and very high temperatures

Recently reported results of the high strain rate, high temperature measurements of the yield strength of tantalum and tungsten have been analyzed along with new experimental results on the yield strength of molybdenum. Thin wires are subjected to high stress by passing a short, fast, high current pulse through a thin wire; the amplitude of the current governs the stress and the repetition rate of the pulses determines the temperature of the wire. The highest temperatures reached in the experiments were 2100°C (for molybdenum), 2250°C (for tantalum) and 2450°C (for tungsten). The strain-rates in the tests were in the range from 500 to 1500 s ^-1. The parameters for the constitutive equation developed by Zerilli and Armstrong have been determined from the experimental data and the results have been compared with the data obtained at lower temperatures. An exceptionally good fit is obtained for the deformation of tungsten.