The nanoscratch hardness of a gold–nickel nanocrystalline nanolaminate at high strain rate

The use of triboindentation testing enables a dynamic range of testing that can span more than eight orders of magnitude in strain rate. The mechanical response of a gold–nickel nanocrystalline nanolaminate is investigated as it is subjected to high strain-rate conditions using the nanoscratch test method. The scratch hardness measurements are compared for scratch widths above which the contributions from grain size and layer pair spacing reaches a plateau and representative interface spacing. It is found that the strain-rate sensitivity increases rapidly beyond a 10+ 3 s− 1 strain rate indicative of superplastic behavior.

► The strain-rate dependence of hardness is measured in Au-Ni nanocrystalline nanolaminates. ► An interface-separation value is computed representative of both layer spacing and grain size. ► Triboindentation is conducted at indent depths beyond a plateau interface-separation value. ► An onset of high strain-rate sensitivity is attributed to nanoscale features smaller than 5 nm.