Synergistic multi-axial compression and isothermal annealing in Al-6wt% and-8wt% Mg alloys for mechanical anisotropy reduction

초록

Plastic anisotropy critically governs the sheet-forming behavior of aluminum alloys. This work investigates multi-axial compression (MAC) of Al-6Mg and Al-8Mg alloys (wt.%) as a route to attenuate anisotropy, followed by isothermal annealing at 350 degrees C for 10-90 min. MAC, implemented via three sequential orthogonal compressive passes (ND -> TD -> FD) at room temperature (total von Mises strain similar to 0.67), produces equiaxed grain morphologies with a weak deformation texture enriched in rotated-Cube and E components. In the as-MAC condition, Al-8Mg exhibits higher stored dislocation density and a more randomized texture relative to Al-6Mg, correlating with improved initial plastic isotropy. Subsequent annealing drives rapid recovery and recrystallization: total dislocation density and geometrically necessary dislocation levels decline, with a pronounced edge-to-screw transition occurring more precipitously in Al-8Mg. Annealing of Al-8Mg promotes larger recrystallized grains and stronger texture components, consistent with its faster recovery kinetics compared to Al-6Mg. The combined MAC-annealing process thus fosters substantial texture randomization, reflected in reduced texture index and suppressed planar anisotropy (Delta r -> 0), while elevating the work-hardening exponent and moderately enhancing the average r-value. These findings demonstrate how MAC-induced weak initial textures and alloy-specific recovery pathways synergize during annealing to yield equiaxed, low-dislocation microstructures that balance strength, ductility, and isotropy.

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