State Key Laboratory of High Performance & Advanced Welding Materials, China Academy of Machinery Zhengzhou Research Institute of Mechanical Engineering Co., Ltd., Zhengzhou 450001, China
Abstract: The Ag/Cu composite strip, replacing Ag with Cu, represents a new generation of fuse material with a wide market application prospect compared with pure Ag fuse material due to its advantages such as saving Ag and reducing cost, meeting the needs of high power, high and low voltage circuit fuse protection. There is an abnormal failure phenomenon that the composite strip breaks along the Ag/Cu interface under low times of overload current instead of breaking at the narrow diameter of pure Ag. For this phenomenon, the abnormal break failure mode and mechanism of Ag/Cu composite strips were revealed by studying the interfacial microstructure evolution, element distribution and electrical properties before and after bending and before and after the low overload current test in different bending processes. The results show that the bending process changes the break failure mode of the composite strips, and when the fold is at the Ag/Cu interface, the local stress causes microcracks around the Ag/Cu interface. When the low-fold overload current passes through the strip, under the role of skin effect in the interface surface layer, the existence of microcracks makes the local resistance increase, causing rapid heat accumulation. A significant number of Cu atoms diffused through the interface to the Ag strip, resulting in the formation of large-sized low-melting point Ag/Cu eutectic zones with lower breaking conditions. Due to the difference in the diffusion rate of Ag and Cu atoms, it easily forms a large number of Kirkendall voids at the interface, which can subsequently expand to create a large crater-like structure through the strip to cause damage, resulting in the strip along the Ag/Cu interface breaking abnormal failure.
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