Nanocrystalline growth and grain-size effects in Au–Cu electrodeposits

Abstract

The processing–structure–property relationship is investigated for electrodeposited foils of the gold–copper alloy system. A model is presented that relates the deposition process parameters to the nanocrystalline grain size. An activation energy of 1.52 eV atom − 1 for growth is determined for a long-pulse (> 10 msec) mode, and is 0.16 eV atom − 1 for short pulses (< 5 msec). The effect of nanocrystalline grain size on the mechanical properties is assessed using indentation measurements. A Hall–Petch type variation of the Vickers microhardness with nanocrystalline grain size (> 6 nm) is observed for Au–Cu samples with 1–12 wt.% Cu as tested in cross-section. The hardness increases three-fold from a rule-of-mixtures value < 1 GPa to a maximum of 2.9 GPa.