Effect of Ca and Y on the Microstructure, Mechanical Properties and Corrosion Properties of Mg-6Zn-1Al Alloy

The effect of trace addition of Ca and Y on the microstructure, mechanical properties and corrosion properties of Mg-6Zn-1Al alloy were investigated. The results show that the second phase in the as-cast ZAM610 alloy consists of alpha-Mg, Mg51Zn20 and a small amount of Al8Mn5 phases. The Mg51Zn20 phase in the as-cast alloy is substituted by Mg-32(Al, Zn)(49) with Ca addition. alpha-Mg, Mg51Zn20, Al2Y and a small amount of Al10Mn2Y phases are found in the Y-containing alloys. Y or/and Ca addition refines markedly the recrystallized grains of the tested magnesium alloys, and the alloy of Y+Ca addition has the minimum grain sizes. In the Ca-containing alloy, MgZn2 phase is dynamically precipitated during extrusion, which has strong effect of Zener retardation, and forms a double-mode microstructure composed of fine recrystallized grain and coarse deformation zone. ZAMX6100 alloy has the highest tensile strength, yield strength and elongation, which are 354 MPa, 313 MPa and 17.3%, respectively. In addition, Al2Y phase in Y-containing alloy promotes recrystallization nucleation during deformation, resulting in a reduction of deformation bands. The improvement of mechanical properties of tested alloys after microalloying can be attributed to the refinement of dynamic recrystallization grains, the formation of Al2Y phase particles and the dynamic precipitation of MgZn 2 phase. For corrosion resistance of the Ca-containing alloy, the raising reason is that a large amount of dynamically precipitated MgZn2 phase prevents the continuous corrosion, while Y element improves the corrosion resistance of the alloy matrix.