Compressive yield strengths of nanocrystalline Cu and Pd

Compression tests were performed on disks of nanocrystalline Cu and Pd. The following observations have been made: • Yield strengths in compression of high density nanocrystalline Cu and Pd samples are very large, of the order of 1 GPa. • The strength is highly dependent on porosity, with a noticeable drop in σy associated with a 1-3% drop in density. • The compressive yield strength for a 98% dense Cu with grain size of 20 nm fits on the Hall-Petch curve extrapolated from coarse-grain data. • Nanocrystalline Cu and Pd samples, which are brittle in tension, undergo extensive compression before failure.