Fatigue of High Purity Copper Wire

Abstract
The fatigue properties of 7N, OFC and Tough-Pitch copper wires were evaluated by a rotational bending method. 7N copper wires, having RRR_300K/4.2K of 7600, were produced by electro-refining, vacuum melting, zonerefining followed by suitable drawing processes, using 4N class commercial OFC plates as the starting material. The fatigue failure cycles of 7N copper increased with an increased pause period imposed during the fatigue test after 5x10⁶ cycles. Remarkable recrystallizations initiated from the wire surface occurred in 7N copper after the pause period in the fatigue test. Strains accumulated during fatigue are considered to act as the driving force. It is expected that 7N copper can recover from fatigue by itself during practical service use and show excellent fatigue resistance.