The effects of burnishing and chemical composition on the structure and mechanical properties of bulk gold–copper electrodeposits were studied. After developing quantitative electron microscopic methods, microstructure-calorimetric and mechanical property correlations were obtained. Burnishing was found to increase the stored energy, hardness and mechanical strength of the deposit by preventing large columnar grain growth and by creating a uniform distribution of dislocations (2.6 to 4.0×1011 cm/cm3), twins (Sν∼3×105 cm2/cm3), and subgrains (Sν=2.2 to 3.2×105 cm2/cm3). When the copper content of the burnished gold-copper deposit was increased from 3.6 to 33.2 at. %, a significant enhancement in stored energy, hardness, and mechanical strength was observed and related to the respective increase in dislocation density (∼1×1012 cm/cm3) and decrease in subgrain size (Sν=5.5×105 cm2/cm3).