Effect of aluminum contents on the microstructure and mechanical properties of magnesium‐aluminum‐calcium alloys

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The effect of aluminum contents on the microstructure and mechanical properties of as‐extruded magnesium‐aluminum‐calcium alloys was systematically investigated. The as‐solid alloys with three aluminum contents contain block‐shape calcium aluminide phases and aluminum‐manganese intermetallic phases. Differently, the amounts of block‐shape calcium aluminide phases and aluminum‐manganese intermetallic phases increased with aluminum contents. During hot extrusion process, the block‐shape calcium aluminide phases and aluminum‐manganese intermetallic phases are fragmented into small pieces and aligned along the extrusion direction. Bimodal microstructures were obtained after extrusion, consisting of fine dynamically recrystallized grains and coarse deformed grains. The area fractions of dynamically recrystallized grains increased from 53 % to 65 % with aluminum contents increasing from 3.12 % to 5.21 %, due to the particle stimulated nucleation mechanism caused by block‐shape aluminum‐containing phases. The as‐extruded magnesium‐aluminum‐calcium alloys show a strong basal fiber texture, which diminished as aluminum contents increase. The strength of as‐extruded magnesium‐aluminum‐calcium alloys diminished as aluminum contents increased. The as‐extruded magnesium‐3.12 aluminum‐2.65 calcium (wt.‐%) alloy demonstrates a yield strength of 366 MPa and an ultimate tensile strength of 391 MPa. The exceptional high strengths are due to the ultrafine dynamically recrystallized grains stabilized by fragmented second phases, strong basal texture and high dislocation density.

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