Cu/Cu₄Ti複相合金線材の低温焼鈍硬化

抄録

Age–precipitable Cu–Ti alloys are widely used in conductive components such as smartphones due to their excellent balance of strength and electrical conductivity. As the demand for miniaturized components increases, further improvements in the strength, workability, and fatigue properties of Cu–Ti alloys will be necessary. According to a previous study, Cu/Cu₄Ti dual–phase alloy wires, which were produced through over–aging and wire drawing, offer a better balance of strength and electrical conductivity compared to conventional Cu–Ti alloy wires. In this study, we aimed to further enhance the strength of Cu/Cu₄Ti dual–phase alloy wires by applying the low–temperature anneal hardening phenomenon. When the Cu/Cu₄Ti dual–phase alloy wires were subjected to annealing at low temperatures of 300〜400°C, their Vickers hardness increased by up to 75 HV, reaching a maximum hardness of 405 HV and a tensile strength of 1660 MPa. Note that the electrical conductivity was maintained or even increased at or above 16 %IACS during low–temperature annealing process. These findings suggest that low–temperature annealing is an effective method for improving the strength of wire–drawn Cu/Cu₄Ti dual–phase alloy wires without compromising their electrical conductivity. Additionally, we observed several key microstructural changes during the low–temperature annealing process, including strain relaxation (a decrease in dislocation density), the introduction of annealing twins, and the segregation of solute Ti around dislocations. These microstructural changes should contribute to the low–temperature anneal hardening in the Cu/Cu₄Ti dual–phase alloy wires.