Effects of doping atoms (X= Dy, Sc, La, Ce) on the generalized stacking-fault of Al–Mg–Si alloys

Stacking faults (SFs) can be manipulated to enhance the mechanical properties of metal materials, particularly the strength. However, SFs are infrequently detected in Al matrix alloys due to the high stacking fault energy (SFE) of pure Al and its limited effect from most alloying elements. Consequently, the reinforcement of Al alloy with SFs has been a long-term challenge. HRTEM reveals the presence of stacking faults in novel La, Dy, and Sc-doped Al-Mg-Si alloys. The Al-Mg-Si-La alloy shows the highest stacking fault density and demonstrates superior ultimate tensile strength and elongation compared to the other doped alloys. The effects of doping elements on stacking faults are quantified by analyzing formation enthalpy ( ΔH f ) values and stacking fault energies of Al-Mg-Si-based alloys at different doping concentrations via first-principles calculations. Adding Dy, Sc, La, or Ce decreases both ΔH f and SFE in these alloys to varying degrees. 2.08 at.% Sc (2Sc atoms) doping reduces the ΔH f value of baseline Al-Mg-Si alloy by 95.36%. And 2.08 at.% La (2La atoms) drastically lower the SFE of baseline Al-Mg-Si alloy by 26.8 %, with the best effect. The physical origin of reducing the SFEs of alloys is attributed to elements doping disturbing the lattice orientation and electronic environment of the matrix atoms, changing the flowability of charges during deformation, thereby enhancing the mechanical properties of the Al-Mg-Si-based alloys.