Effects of the SiC/Al interface reaction on fracture behavior of a composite conductor using SiC fiber reinforced aluminum for next generation power equipment

Electrical power demands are increasing every year, meaning that lightweigh t electric cable is needed which has high transmission capacity, high therm al resistance and low sag. Tokyo Electric Power Co., Chubu Electric Power C o. and Hitachi Cable Ltd. have been breaking new ground in the field of ele ctric cable through the development of a SiC fiber reinforced aluminum cond uctor. In this work, the SiC/Al interface reaction during the manufacturing process and the electricity transmission temperature were studied by trans mission electron microscopy (TEM), energy dispersive X-ray spectroscopy (ED X) and field emission-Auger electron spectroscopy (FE-AES) for long-term re liability assessment. No reaction products were detected at the SiC/Al inte rface of elemental wire consisting of 7 SiC/Al preformed wires, indicating that the wire manufacturing process was reliable. An Al4C3 product was dete cted locally at the SiC/Al interface of the wire which had been thermally t reated in molten Al under unfavorable conditions. The activation energy, Q, of Al4C3 growth at the SiC/Al interface was about 190 kJ/mol. In the tempe rature range of electricity transmission, Al atoms diffused into SiC fiber during heat treatment, and the amount of the diffused Al increased with inc reasing treatment temperature and holding time. The activation energy of Al diffusion through the SiC/Al interface to SiC fiber was about 78 kJ/mol. S trength deterioration was not induced by Al diffusion into SiC fiber, but s trength strongly depended on the formation of Al2SiO5 compound at the SiC/A l interface above 400 degrees C transmission temperatures. Kinetics calcula tions indicated that the rate of strength deterioration of the composite ca ble, held at 300 degrees C for 36 years, was about 5%, so that practical us e of SiC/Al composite cable should not be far in the future. (C) 1999 Kluwe r Academic Publishers.