Influences of pulse plating parameters on chemical composition, grain size, morphology, and mechanical property of Au-Cu alloy films electrodeposited with an Au-rich sulfite-based electrolyte were investigated. A wide range of Cu concentration (wCu) varied from 3.5 to 26.7 wt% was attained in the Au-Cu films. The galvanic displacement reaction occurred during the off-time period showed great influences on the composition and the grain size. Meanwhile, surface morphology of the Au-Cu films was interrelated with the alloy composition. An increase in the pulsed current density lead to roughening of the surface, and smoothening of the surface was achieved by promoting the displacement reaction. Micro-mechanical properties of the Au-Cu films were evaluated by micro-compression tests for applications as movable micro-components in electronic devices. A pronounced high yield strength at 1.38 GPa was achieved in the Au-Cu film with the smallest grain size at ca. 4.40 nm and the wCu at ca. 15 wt%, which is suggested to be a result of synergetic effects of grain boundary strengthening and solid solution strengthening mechanisms. (c) 2018 The Electrochemical Society.