Ligament size effect in creep of nanoporous gold

•Spherical nanoindentation creep tests were performed on nanoporous gold samples with ligament sizes of 30, 103, 417, and 986 nm.•Ligament-size dependent creep was observed in terms of total creep strain and creep rate for ligament sizes ranging from 103 nm to 986 nm while the greatest creep is shown for ligament size of 30 nm.•By coating a thin amorphous alumina layer on nanoporous gold, creep increased in the range of ligament sizes from 103 nm to 986 nm while creep decreased for ligament size of 30 nm.•The primary creep mechanism was regarded as the dislocation-mediated creep for all ligament sizes, but the governing dislocation source was different stochastically; dislocation was dominantly carried by dislocation nucleation at the surface for ligament size of 30 nm, while it was gradually controlled by initial dislocation sources as increasing ligament size. Spherical nanoindentation creep tests are conducted on four nanoporous gold samples with ligament sizes of 30, 103, 417, and 986 nm. We find the ligament-size dependent creep, increase of total creep strain and creep strain rate with increasing ligament size, in the range of ligament sizes from 103 nm to 986 nm while the most pronounced creep is shown for ligament size of 30 nm. By coating a 2-nm-thick alumina layer on the ligaments, creep increased for ligament sizes ranging from 103 nm to 986 nm, while it decreased for ligament size of 30 nm. The ligament-size dependent creep and effect of surface coating are discussed with dominant dislocation mechanism in the ligaments under the dislocation-mediated creep for each ligament size. [Display omitted]