Microstructure, Mechanical Properties, and Strengthening Mechanisms of Extruded Mg-1Nd-1Mn Alloys with Different Zn

Microstructures and mechanical properties of the extruded Mg-1Nd-1Mn-xZn (NMZ11x, x = 0, 1 and 2 wt.%) alloys were explored. The NMZ110 alloy exhibits a partial dynamically recrystallized (DRXed) microstructure containing fine DRXed grains and coarse unDRXed grains. 1 wt.% Zn addition leads to more uneven distribution microstructure and then becomes uniform microstructure after 2 wt.% Zn addition. This phenomenon is attributed to the altered Mg₁₂Nd particle size and distribution. The volume fractions of Mg₁₂Nd particles were raised with the increase of Zn addition and the distribution of coarse Mg₁₂Nd particles becomes uneven firstly and then evolves uniform. In addition, the texture was continuously strengthened with increasing Zn addition (the basal panel of most grains tilting 40 ± 5° along the extrusion direction, ED, changed to the basal panel of most grains paralleling to ED, typical strong basal texture). The change of texture characteristics was mainly affinitive with the decreasing concentration of Nd solute in matrix influenced by increasing Mg₁₂Nd particles. The tensile test showed that Zn addition gradually enhanced the tensile strengths of extruded NMZ11x alloy bars, obtaining the highest yield strength of 212 MPa and ultimate tensile strength of 267 MPa (NMZ112). The increasement of strengths was mainly ascribed to Zn solution strengthening, Mg₁₂Nd particle strengthening and texture strengthening. Besides, adding Zn element can reduce the elongation of the NMZ11x alloy bars. This decrease was mainly associated with increasing coarse Mg₁₂Nd particles and the strong basal texture.