Tension-compression asymmetry in plasticity of nanoporous gold

Abstract

Tensile and compressive tests are carried out on four nanoporous gold samples with ligament sizes of 56, 149, 402, and 868 nm, all without grain boundaries and with similar number of ligaments regardless of ligament size. We find that tensile yield strengths are greater than compressive yield strengths up to ligament size of 402 nm, while yield strengths are similar in tension and compression for dL of 868 nm. The dependence of tensile yield strength on ligament size is described well using a size-effect exponent -1.18 for four samples, whereas bulk-like behavior, i.e. no ligament-size dependency, is observed for ligament size greater than 402 nm in compression; compressive yield strength depending on ligament size is described by a size-effect exponent -1.49 for ligament sizes ranging from 56 nm to 402 nm. The asymmetries in yield strength and plasticity between tension and compression are discussed in terms of the deformation behavior of individual ligaments based on a suggested open-cell model and dislocation activities in the ligaments.