Low‐Temperature Annealing of Asymmetrically Cold‐Rolled Electrolytic Tough‐Pitch Copper: Anneal Hardening and Bimodal Microstructure

Abstract

In this research, 90% asymmetric unidirectional rolling and post‐annealing are applied to electrolytic tough‐pitch (ETP) copper. The effect of low‐temperature (200 °C) annealing on the microstructure and texture evolution, mechanical, and electrical properties are investigated. Static recovery (SRV) is the main softening mechanism at the annealing time range of 1–5 min. In contrast, complete static recrystallization (SRX) is observed after annealing for 10 min. Bimodal microstructure, consisting of coarse and fine grains, is evolved for annealing times more than 10 min. With increasing the post‐annealing duration, the intensity of deformation and shear textures is continuously decreased; however, the recrystallization (Cube) orientation becomes stronger up to 11.2 × R. After 1, 2, and 5 min of post‐annealing, the hardness, yield strength, tensile strength, ductility, and toughness of copper are higher than those of the 90% rolled sample due to annealing hardening. After 10 min of annealing, the hardness, yield strength, and tensile strength suddenly decrease and the ductility and toughness significantly enhance owing to the complete recrystallization. With increasing the post‐annealing time, the fraction of flat surfaces is decreased and the fraction of ductile dimples is increased. With the post‐annealing time increasing from 1 to 120 min, the electrical conductivity gradually increases from 84.9%IACS to 96.7%IACS.