Effect of microalloying with Ca on the microstructure and mechanical properties of Mg-6 mass%Zn alloys

• The divorced Mg4Zn7 in the as-cast Mg-6Zn alloy was replaced by lamellar Ca2Mg6Zn3 with increasing Ca addition.
• Ca addition refined the microstructure, promoted dynamic precipitation and inhibited dynamic recrystallization.
• Ca addition improved strength of Mg-6Zn alloys, attributed to fine grains, high density precipitates and strong texture.

The Mg-6 mass%Zn alloys microalloyed with different amounts of Ca were cast and extruded. The second phase in the as-cast Mg-6Zn alloy is Mg4Zn7, which is replaced by Ca2Mg6Zn3 with an increase of Ca addition. Microalloying by Ca affects the grain size, dynamic recrystallization, and dynamic precipitation of Mg-6Zn alloys during extrusion. The Ca addition inhibits dynamic recrystallization and grain growth due to the pinning effect of fine precipitates, giving rise to fine dynamic recrystallized grains. A large amount of precipitates is observed in the Ca containing alloys after extrusion. Ca effectively improves strength of the as-extruded Mg-6Zn alloy, which is mainly attributed to refined dynamic recrystallized grains, dense precipitates, and deformed regions with high-density dislocations and strong basal texture.

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