Microstructural control in extruded magnesium alloys: A quantitative analysis of processing conditions and solutes

Accelerating the development of wrought Mg alloys requires quantitative links between extrusion conditions and dynamically recrystallized microstructures, yet existing approaches remain largely empirical and rarely treat solute chemistry and deformation heating in a unified manner. Here, we develop a quantitative framework to predict grain size and basal-oriented grain fraction in extruded Mg alloys by (i) separating basal-oriented and non-basal-oriented DRX grain populations and (ii) introducing a modified Zener-Hollomon parameter that simultaneously incorporates strain rate, the steady-state temperature rises during extrusion, and the solute grain-boundary segregation energy. Model Mg-1 at. %Al, Mg-1 at. %Zn and Mg-1 at. %Gd alloys were extruded over broad temperature and strain-rate windows and characterized by EBSD, while finite-element simulations were used to quantify the deformation-induced temperature increment. The framework captures the monotonic grain coarsening with extrusion temperature and the non-monotonic strain-rate dependence arising from the competition between deformation heating (enhanced boundary mobility) and reduced time available for boundary migration and substructure evolution. It further rationalizes the rare-earth texture transition by quantifying the relative nucleation-growth advantages of non-basal grains under strong solute drag, explaining the simultaneous grain refinement and basal-texture weakening in Mg-Gd. With parameters regressed from the experimental dataset, the model predicts the average grain size and the basal-grain volume fraction with errors typically below 20% and 15%, respectively, and remains robust when validated under an additional extrusion condition. The proposed relationship enables rapid processing-microstructure mapping and provides transferable descriptors for designing extrusion schedules and solute selections toward tailored microstructures in wrought Mg alloys.