Exploring the evolution of texture and properties of ultrafine copper wire during high strain drawing process

The ultrafine copper wire with a diameter of 18 mu m is prepared via cold drawing process from the single crystal downcast billet (Phi 8 mm), taking a drawing strain to 12.19. In this paper, in-depth investigation of the microstructure feature, texture evolution, mechanical properties, and electrical conductivity of ultrafine wires ranging from Phi 361 mu m to Phi 18 mu m is performed. Specially, the microstructure feature and texture type covering the whole longitudinal section of ultrafine wires are elaborately characterized. The results show that the average lamella thickness decreases from 1.63 mu m to 102 nm during the drawing process. Whereas, inhomogeneous texture evolution across different wire sections was observed. The main texture type of copper wires are components of <111>, <001> and <112> orientations. Specifically, the peripheral region is primarily dominated by <111> and <112>, while the central region is <001> and <111>. As the drawing strain increases, the volume fraction of hard orientation <111> with low Schmid factor increase, where notably higher fraction of <111> is result from the consumption of <112> and <001> for the wire of Phi 18 mu m. For drawn copper wire of 18 mu m, superior properties are obtained with a tensile strength of 729.8 MPa and an electrical conductivity of 86.9% IACS. Furthermore, it is found that grain strengthening, dislocation strengthening, and texture strengthening are three primary strengthening mechanisms of drawn copper wire, while the dislocation density is main factor on the reducing of conductivity.