Mechanisms behind the macro- and microscopic behaviors of the electric heated Al–Mg–Si alloy wires

The Al–Mg–Si alloy wire for overhead transmission line is in thermal service due to the interaction between electric current and microstructure during power transmission, which could affect its microstructure and properties. At present, researchers generally use the traditional annealed-heated (A-H) treatment to simulate the thermal service state of Al–Mg–Si alloy wire, which could not consider the additional effect of electrons on the microstructure and properties. Therefore, in this research, the Al–Mg–Si alloy wire was treated at various temperatures generated by the electric-heated (E-H) treatment using an electric current input device. The mechanisms behind the evolution of microstructures, strength and electrical conductivity of the E-H Al–Mg–Si alloy wire were revealed and compared with those of the A-H Al–Mg–Si alloy wire. The experimental results show that with increasing the E-H temperature of the Al–Mg–Si alloy, its strength decreased and the electrical conductivity increased, which may be attributed to the growth of radial grains and the coarsening of precipitates. In addition, the effect of E-H treatment on Al–Mg–Si alloy wire is different in various temperature ranges. In the low-temperature region (90 °C–110 °C) and the high-temperature region (200 °C), the strength and the electrical conductivity of the E-H and A-H Al–Mg–Si alloy wires are nearly the same. In contrast, in the medium-temperature region (160 °C–185 °C), the E-H Al–Mg–Si alloy wire has lower strength and higher electrical conductivity than the A-H Al–Mg–Si alloy wire, which is mainly due to the accelerated coarsening of precipitates caused by the local overheating around precipitates generated by the input electric current. •Electrothermal service state of Al alloy wire was simulated by experimental design.•Electric-heated Al alloy wire has lower strength and higher electrical conductivity.•Electric-heated treatment accelerates the coarsening of precipitate due to Joule heat.