• High strain cold drawing of single-crystal copper produces 18 μm ultrafine wire with a tensile strength of 729.8 MPa and electrical conductivity of 86.9% IACS.
• As drawing strain increases, the average lamella thickness refines dramatically from 1.63 μm to 102 nm.
• Texture evolution is inhomogeneous: <111> and <112> dominate the periphery, while <001> and <111> dominate the center; hard <111> orientation grows at the expense of <112> and <001>.
• Grain, dislocation, and texture strengthening are the primary strengthening mechanisms, with dislocation density being the main factor reducing electrical conductivity.