Changes in Mechanical Characteristics of Pre-Annealed Wires of Cu-Sn Alloy Manufactured by Continuous Draw Bending

Abstract

The changes in mechanical properties and microstructures of fine Cu–Sn alloy wires manufactured by deep wire drawing and heat treatment, and of the wires deformed by draw bending were systematically investigated. During draw bending, the wires were subjected to the compressive/tensile or tensile/compressive strain in the longitudinal direction. As a result, it was confirmed that the softening caused by plastic deformation was induced when easing up the wire drawing strain by heat treatment were few, such as the decreasing strength and increasing elongation. Work hardening was induced when easing up the wire drawing strain by heat treatment were large, such as the increasing strength and decreasing elongation. With decreasing strength of softening induced by plastic deformation, increase in grain size is smaller than the strength deterioration. Additionally, it was confirmed that the occupancy probability of high-angle grain boundaries increases. This can be understood by considering that the many dislocations formed inside the grains are piled up in one direction during draw bending. Additionally, it is considered that ductility enhancement is caused by the increase in work hardening rate induced by the piled up dislocations.