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

Abstract

The ultrafine copper wire with a diameter of 18 µm is prepared via cold drawing process from the single crystal downcast billet (Φ8 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 Φ361 µm to Φ18 µm 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 µm 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 Φ18 µm. For drawn copper wire of 18 µm, 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.

Keywords

Copper wires / ultrafine wire / drawing / texture evolution / tensile strength

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