Formation and evolution of nanoporous bimetallic Ag-Cu alloy by electrochemically dealloying Mg-(Ag-Cu)-Y metallic glass

•Uniform nanoporous Ag-Cu alloy was fabricated by dealloying Mg-based metallic glass.•The nanoporous structure was built up with numerous Ag-Cu ligaments.•The nanoporous ligaments show two-stage coarsening behavior with dealloying time.•The formation and evolution mechanisms of the nanoporous structure were clarified.•It could provide new guidance to the synthesis of nanoporous multi-component alloys. A three-dimensional nanoporous bimetallic Ag-Cu alloy with uniform chemical composition has been fabricated by dealloying Mg65Ag12.5Cu12.5Y10 metallic glass in dilute (0.04M) H2SO4 aqueous solution under free-corrosion conditions. The nanoporous Ag-Cu evolves through two distinct stages. First, ligaments of the nanoporous structure, consisting of supersaturated Ag(Cu) solid solution with a constant Ag/Cu mole ratio of 1:1, are yielded. Second, with excessive immersion, some Cu atoms separate from the metastable nanoporous matrix and form spherical Cu particles on the sample surface. Formation and evolution mechanisms of the nanoporous structure are proposed.