• Mn content critically modifies the microstructure and texture of hot-extruded Mg–2Nd–1Gd, with 0.5wt% Mn yielding the optimal combination of strength and ductility.
• The Mg–2Nd–1Gd–0.5Mn alloy achieves a yield strength of 138.0 MPa, ultimate tensile strength of 231.1 MPa, and elongation of 38.8%.
• Solid-solution Mn atoms reduce Nd/Gd segregation and weaken solute drag, while α-Mn particles pin grain boundaries and delay recrystallization.
• Grain boundary and dislocation strengthening dominate the yield strength of the 0.5Mn alloy, contributing 44% and 24.1%, respectively.