High Strength and Electrical Conductivity of Al‐Fe Alloys Produced by Synergistic Combination of High‐Pressure Torsion and Aging

Abstract

A synergistic combination of high-pressure torsion (HPT) and artificial aging was attempted in Al-Fe alloys to achieve high strength and high electrical conductivity. HPT produced an ultrafine-grained structure and supersaturation of Fe in the matrix, resulting in high strength above 500 MPa. Aging after the HPT processing increased the electrical conductivity well over 50 IACS% while simultaneously increasing the yield strength above 600 MPa via precipitation of dissolved Fe. The results demonstrate that Al containing a low fraction of Fe (2 wt%) should be a good candidate for a high strength, light weight, and high-electrical-conductive material.

Structure and mechanical behavior of ultrafine-grained aluminum-iron alloy stabilized by nanoscaled intermetallic particles

“…2(a) shows the typical as-cast dendritic structure with pro-eutectic zones in dark (zone A) and Fe-rich eutectic zones in bright (zone B). Similar as-cast structures have been described in previous works [5][6][7]29,[43][44][45][46]. The HAADF STEM image ( Fig. 2(b)) shows similar zones at a higher magnification and clearly exhibits in bright the fine-scaled intermetallic particles within the eutectic areas (labeled B and B').…”

“…The equilibrium grain sizes for the as-deformed Al-2%Fe alloy have been estimated from eq(4) and eq (5), assuming that all intermetallic particles are from the Al6Fe phase (Table 3). Theoretical estimates of grain sizes for as-HPT microstructures are systematically larger than experimental values.…”

“…However, controlling their size and dispersion by a precipitation treatment is impossible since they are stable up to the liquidus temperature. However, when subjected to SPD, these brittle intermetallic particles can be fragmented and dispersed [25][26][27][28] or could even be dissolved within the matrix [5,7,[26][27][28][29][30][31].…”

“…It clearly indicates that a huge strain (1000 revolutions, corresponding to a shear strain of 55000) is necessary to achieve a near complete fragmentation of the original coarse intermetallics to the STEM Dark Field (a, b, c) and STEM HAADF (d, e, f, g, h, i) images after HPT with N = 10 revolutions (a, d, g), N = 100 revolutions (b, e, h) and N = 1000 revolutions (c, f, i) nanoscale with a nearly uniform distribution of final particles. Electron diffraction in the TEM and TEM-EDS was applied on a large number of nanoscaled particles resulting from the fragmentation process (see supplementary material), and they all exhibited the crystallographic structure of the Al6Fe phase, indicating that no significant strain-induced phase transformation occurred during the HPT process.It has been shown in the literature that intermetallic particles could be partly dissolved during SPD[5,6,[26][27][28][29][30]53]. Measuring the volume fraction of intermetallic particles from STEM-HAADF images was only possible after 1000 revolutions where particles are homogeneously distributed and where it is possible to obtain representative data from a limited number of images.…”

Optimization of Strength‐Electrical Conductivity Properties in Al–2Fe Alloy by Severe Plastic Deformation and Heat Treatment

“…Moreover, bauxite ore contains up to 5% iron, which means that alloying is not needed . Secondly, solubility of iron in aluminum for conventionally processed alloys at room, and up to near‐melting, temperatures is close to zero . This eliminates the major contributor to electrical resistivity, that is, solid solute atoms (the other contributors are grain boundaries, particles, and dislocation density) …”