| This paper presents a study on the influence of minor additional torsional strain by Δγ ˜ 0.036 at room temperature on the microstructure, mechanical and electrical properties of the ultrafine-grained (UFG) alloy of the Al-Mg-Si system that has been preliminarily subjected to complex treatment by severe plastic deformation at room and elevated temperatures (with a total strain γ=6.54). The optimal regime of additional strain (Δγ ≈ 0.024) is reported, showing the best combination of strength and electrical properties, particularly an increase in the ultimate tensile strength by ~14% while maintaining the electrical conductivity at ~56% IACS. This is achieved by introducing additional dislocation density while preserving other microstructural parameters such as grain size, the volume and distribution of secondary phases, the distribution of grain boundaries by misorientation. The contributions of various mechanisms to the hardening and charge scattering are estimated as a function of the value of Δγ and the estimates are in good agreement with the experimental data when Δγ ˜ 0.024 and most likely indicate to the start of dissolution of Mg2Si secondary phase nanoparticles at larger additional strain (Δγ ≈ 0.036), which leads to additional strengthening but sacrifices electrical conductivity. |
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