High-pressure torsion for fabrication of high-strength and high-electrical conductivity Al micro-wires

Iron (Fe) is commonly found in aluminum (Al), but its contents are usually kept as low as possible, because the formation of intermetallic phases may induce fracture. In this study, high-pressure torsion (HPT) was used to control the microstructure in an Al-2 %Fe alloy in conjunction with wire drawing and an aging treatment, in order to improve not only their mechanical properties but also the electrical conductivity. It is shown that HPT processing of ring-shaped samples produced ultrafine grains with a size of ~150 nm in the matrix, while intermetallic phases were fragmented to nanosizes with some Fe fraction dissolved in the matrix. Semi-rings were extracted from the HPT-processed samples and swaged to a round section with 0.4-mm diameter. The HPT-processed sample was successfully drawn to a final diameter of 0.08 mm (25:1 ratio, 96 % reduction in area), whereas the sample without HPT processing failed after drawing to 0.117-mm diameter (12:1 ratio, 91 % reduction in area). The electrical conductivity increased to ~65 IACS % in the HPT-processed rings and to ~54 IACS % in the wires by aging for 1 h after the drawing.