Improving microstructural and mechanical response of new AZ41 and AZ51 magnesium alloys through simultaneous addition of nano-sized Al 2O3 particulates and Ca

Abstract

In the present study, new magnesium based AZ41/Al2O 3-Ca and AZ51/Al2O3-Ca nanocomposites were successfully synthesized incorporating varying amount of elemental Al (1 and 2% by wt.), Ca (1 and 2% by wt.) and 1.5 vol.% nano-sized (50 nm) Al 2O3 particulates into AZ31 alloy using disintegrated melt deposition technique. AZ41 and AZ51 alloys were also developed following the same processing route by adding 1 and 2 wt.% Al, respectively. All alloy and composite samples were then subsequently hot extruded at 400 C and characterized. Microstructural characterization studies revealed equiaxed grain morphology, reasonably uniform distribution of nanoparticulate and intermetallics in the matrix, good interfacial integrity and minimal porosity. Addition of nano-sized Al2O3 particulates and Ca into AZ41 and AZ51 samples helped to reduce the average grain size and diameter of Mg17Al12 second phase and introduced (Mg,Al)2Ca phase in the matrix. Microhardness test results revealed that AZ51/Al 2O3-2Ca samples exhibited around 47% and 90% higher microhardness value when compared to monolithic AZ51 and AZ31 samples, respectively. Room temperature tensile test results also revealed that newly developed nanocomposites exhibited superior combination of tensile properties in terms of 0.2% yield strength, ultimate tensile strength and ductility when compared to their respective alloys and some commercially available Mg alloys. © 2013 Elsevier B.V. All rights reserved.