Simultaneous improvement of mechanical strength and electrical conductivity in Al-2.5 wt% Fe alloy rods with high thermal stability by high-pressure torsion extrusion

The high-pressure torsion extrusion (HPTE), a severe plastic deformation (SPD) method, was applied to process rods of as-cast Al-2.5 wt% Fe alloy (Al-2.5 Fe). This technique effectively overcomes the typical trade-off between mechanical strength and electrical conductivity (EC) commonly observed in Al-alloys. Through the HPTE process, the yield strength increased from 110 MPa to 268 MPa, while the EC increased from 37.3 % IACS to 44.7 % IACS. Furthermore, the ultrafine-grained structure of the HPTE-processed Al-2.5 Fe exhibits remarkable thermal stability, maintaining its strength following annealing for 1 h at 230 °C. The effects of the HPTE-induced deformation and subsequent annealing on the microstructure were thoroughly studied using automated crystal orientation mapping (ACOM), STEM-EDX, and X-ray tomography (NanoCT). In terms of the Al matrix, grain refinement resulted in grains with an average size of 300 nm. Additionally, the previously continuous Al 13 Fe 4 phase network fragmented into micrometer- and nanometer-sized particles. A theoretical analysis has shown a correlation between microstructural characteristics, mechanical strength, and EC, identifying the mechanisms responsible for the strengthening effect and the changes in EC. It indicates that the size, shape, and spatial distribution of the Al 13 Fe 4 phase are crucial in determining mechanical performance, as well as affecting the thermal stability and EC of Al-2.5 Fe. • Enhanced Al-2.5 Fe alloy with improved strength and conductivity via HPTE. • Electrical conductivity improved from 37.3 % IACS to 44.7% IACS with strength increasing simultaneously. • Ultrafine-grained alloy maintains strength and increased conductivity after 230 °C annealing for 1 h. • Correlation established between microstructure evolution and electrical/mechanical properties.