The Microstructure Study on the High-flexible Conductors for Charging Pile Cable Applications

As the urgent requirement for the sustainable development and green energy, the development of electric automobile technology is progressing fast in the recent years. The electric cable connecting the pile and the car during charging plays an important role on the performance of the charging station. Besides the electric properties, the mechanical behavior of charging pile cable, especially the fatigue of high-flexible conductors, has been considered as one of the central issue, which highly relies on the their microstructure characteristics. In this study, we have conducted the microstructure studies on four different types of high-flexible copper conductors by using X-ray diffraction (XRD), optical microscope (OM) as well as scanning electron microscope (SEM). The results show that three of the specimens show very uniform microstructure with homogeneous distribution of grain size from inner part to the outer part of the conductors, which all show more inferior mechanical performances. In contrast, the high-flexible conductor with superior mechanical performance exhibits a special “gradient” microstructure, which has a non-uniform distribution of grain size showing larger grain size with fibrous texture for the inner portion and smaller grain size in the outer portion. And the excellent mechanical performance has been ascribed to finer grain and such a gradient microstructure, which contains the outer layer of equiaxed grains providing enough ductile and electrical conductivity, and the inner layer of fibrous grain can gurantee strength of the conductor. Our work reveals the microstructure characteristics for high-flexible conductors, and provides guideline for the designning of high-performance conductors for charging pile cable applications.