FATIGUE OF HIGH-PURITY COPPER WIRE

.The fatigue properties of 7N, OFC and Tough-Pitch copper wires were e valuated by a rotational bending method. 7N copper wires, having RRR(3 00K/4.2K) of 7600, were produced by electro-refining, vacuum melting, zone-refining followed by suitable drawing processes, using 4N class c ommercial OFC plates as the starting material. The fatigue failure cyc les of 7N copper increased with an increased pause period imposed duri ng the fatigue test after 5x10(6) cycles. Remarkable recrystallization s initiated from the wire surface occurred in 7N copper after the paus e period in the fatigue test. Strains accumulated during fatigue are c onsidered to act as the driving force. It is expected that 7N copper c an recover from fatigue by itself during practical service use and sho w excellent fatigue resistance.