Thermal stability of Al–Zr-Sc conductor alloys during long-term elevated-temperature exposures

Abstract

Four Al–Zr-Sc conductor alloys with 0.1–0.18 wt% Zr and 0.1–0.15 wt% Sc were processed through casting, hot rolling, heat treatments, and cold wire drawing. The mechanical properties and electrical conductivities of the alloy wires were evaluated, and the microstructures were characterized using scanning electron microscopy, transmission electron microscopy, and electron backscattering diffraction techniques. The thermal stabilities of these alloys were systematically assessed during thermal exposures at 310, 350, and 400 °C for up to 1000 h. The ultimate tensile strengths (UTSs) of four Al–Zr-Sc alloy wires reached 206–214 MPa, while the electrical conductivities were 57%–57.5% IACS. All four alloy wires were strengthened by a large number of Al₃(Sc,Zr) nanoprecipitates. With the increase in Zr or Sc content, the UTS only slightly increased, which shows a low impact of the Zr and Sc levels on the tensile strength and electrical conductivity. Notably, remarkable reduction in tensile strength and change in the deformed grain structure were not observed for the four alloy wires during thermal exposure at 310 °C for up to 1000 h. After thermal exposure at 350 °C for 200 h, all four wires still exhibited excellent thermal stabilities. With prolonged exposures at 350 and 400 °C, the alloy wires became unstable. The high-Zr-content Al-0.18Zr-0.1Sc and Al-0.18Zr-0.15Sc alloys exhibited better thermal stabilities after long-term thermal exposures at 350 and 400 °C. This study on the thermal stability of Al–Zr-Sc conductor alloys under extreme conditions provides a valuable reference for industrial applications of thermally resistant Al conductor wires.