Strain-Rate Sensitivity of Nanocrystalline Cu-10Ta to 700,000/s

Several miniature Kolsky bars are used to obtain stress-strain curves for nanocrystalline Cu-10Ta over a range of high strain-rates. The smallest bar (steel) has a 305 mu m diameter, and achieved rates up to 700x10(3)/s. Different sample sizes are needed to obtain different strain-rates, and it is shown that there is no appreciable sample size effect when different sizes are tested at similar strain-rates, even though the sample sizes vary by over an order of magnitude. No significant increase in strain-rate sensitivity is noted over the strain-rate range studied, i.e., the strength increases linearly with the logarithm of strain-rate from 0.001/s to 700 x 10(3)/s.