Al-driven magnesium alloy functionality via manifold structuring and disorder

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Magnesium alloys have had wide, historic industrial and societal impact, Mg-Al-Zn (Magnesium-Aluminum-Zinc) ones in particular for their lightweight structural applications due to a high strength:weight ratio, good castability and machinability. Yet, there is limited comprehensive atomistic-level insights resolving the effects of alloying and porosity on structural and mechanical evolution, especially under load. Herein, we investigated the mechanical behavior of Mg-Al-Zn alloys under uniaxial tensile loading using computational molecular dynamics simulations. A range of alloy compositions (0–18% total Al and Zn) and porosity levels (0–3%) were modeled to assess their influence on strength, phase stability, and mechanisms of structural deformation. Results show that increasing Al and Zn content accelerates the transformation from the hexagonal close-packed (HCP) crystalline phase to more ductile non-HCP phases (eg. FCC), leading to reduced tensile strength and fracture strain at higher alloying levels. In particular, pronounced declines in HCP content immediately preceded fracture, followed by post-fracture stabilization, with intermediary amorphisation observed. Moderate alloying improves mechanical performance, yet excessive additions (>4%) introduce structural instability. Porosity further compromises strength by acting as a stress concentrator, promoting early dislocation activity that correlates with localized phase transformation through atomic diffusion. Metallic/alloy grain-refinement and dislocation analyses revealed that porous alloys undergo more heterogeneous deformation, with earlier dislocation onset and reduced elastic modulus with respect to non-porous systems. In contrast, non-porous alloys exhibit more uniform grain evolution and delayed failure. Overall, the result trends highlight the critical interplay between alloying content and porosity in governing phase transformation, deformation behavior, and mechanical performance. This work provides insight and inroads into the rational design and optimization of alloys with tailored porosity and alloying content for specific applications requiring enhanced mechanical performance, with forward vision to the characterization by advanced operando techniques (e.g., neutron scattering, positron annihilation).