Effect Of Zr On The Microstructure And Properties Of Aluminum Alloy Conductor

Aluminum alloy conductor is widely used in overhead transmission line. Despite its light weight, good electrical conductivity, its poor heat-resistance can not satisfy the need of large capacity and large span. Adding Si, Mn, Cu, Ni and other elements can improve heat-resistance limitedly at the cost of electrical conductivity. Studies show that adding a small amount of Zr can increase the recrystallization temperature of conductor, consequently improve the heat-resistance significantly while has little effect on electrical conductivity. Therefore, heat-resistant aluminum alloy conductor with high allowable temperature, large current capacity, good creeping characteristics has obvious economic benefit and extensive application prospect. Yet the study of heat-resistant aluminum alloy conductor has still great shortage in our country. At present there is no unified products and technical standards, meanwhile no sufficient operating experience, therefore there has been no uniform standards prior to the safety evaluation.On the basis of the dependence of microstructure, tensile strength at high and normal temperature, long-time heat-resistance, electrical conductivity on alloy element content, the relationship between Zr content and heat-resistant aluminum alloy conductor's property was investigated. As a result conductor's property was estimated from Zr content, realizing fast test on heat-resistant aluminum alloy conductor.The variation of electrical conductivity, tensile strength and corrosion-resistance of the conductor with Zr content was investigated using DC double bridge, computer-controlled electronic universal testing machine and electrochemical testing instrument. The results show that the electrical conductivity gradually declined with increase in Zr content and temperature. After short-time and long-time heating treatment and cooling, electrical conductivity increased with increasing heat temperature and hold time. With increasing Zr content conductor's heat-resistance was improved. Heat-resistant aluminum alloy conductor containing Zr could be used for long time at 150℃The conductor containing 0.08% Zr could be used for short time at 180℃. After corrosion in 0.5 mol/L H2SO4 solution, conductor appeared obvious passivation. Eventually a proof passive film formed at the surface of conductor, corrosion products was Al2O3. The corrosion-resistance of aluminum alloy conductor reduced after adding Zr element.Meanwhile the change of microstructure was studied by using transmission electron microscope. The results show that the microstructure of conductor was composed of elongated grains. Grain was refined with the increase in Zr content. Grain became larger after heating treatment, but the grain in conductor containing Zr was still finer than that in common conductor. Adding Zr element inhibited the recrystallization of deformation grain. After long-time heating treatment at 150℃and 180℃, recrystallization phenomenon and a large number of dislocation wall and dislocation cells were observed in all conductors. The dispersed and tiny second phase particle was observed in conductor containing 0.08% Zr.