oa Effect of Nano-Size Al2O3 and Elemental Ca Addition on the Microstructural and Mechanical Properties of AZ41 Magnesium Alloy

Light weight structural materials are in high demand these days due to the limited oil and gas reserves and global inclination to reduce the green house gas (CO2) emission. Magnesium based materials are the lightest engineering materials in the earth. Magnesium alloys that contain aluminium and zinc are known as AZ alloys. These alloys are reasonably priced, easily available, and used in many engineering applications. Various attempts have been made in recent years to further improve the properties of these alloys through the addition of rare earth elements, calcium (Ca), silicon (Si) as well as adding different types of nanoparticles. The addition of Ca has been shown to assist in grain refinement and enhancing corrosion resistance as well as thermal and mechanical properties of magnesium alloys while Nano-sized particles helps to improve ductility, in general.

In the present study, new AZ41/1.5Al2O3-1Ca magnesium Nano composite was successfully synthesized by simultaneously adding 1 wt. % aluminium, 1 wt.% Ca and 1.5 vol.% Nano-sized Al2O3 (50 nm) into AZ31 matrix using an innovative disintegrated melt deposition technique. AZ41/Al2O3 Nano composite was also developed following the same processing route except adding Ca. All Nano composite samples were then subsequently hot extruded at 400 °C and characterized. Microstructural characterization studies revealed uniaxial grain size, reasonably uniform distribution of intermetallic and minimal porosity. Addition of Ca helped to reduce the average grain size of AZ41-Al2O3 Nano composite. Physical properties characterization revealed that the addition of Nano-sized alumina helped to reduce the coefficient of thermal expansion (CTE) of AZ41 alloy and the CTE value further reduced with Ca addition. The presence of Ca also assisted in improving overall mechanical properties including micro hardness, 0.2% yield strength, ultimate tensile strength, and work of fracture without compromising ductility when compared to AZ41 alloy and its alumina Nano composite.

The results suggest that these newly developed magnesium Nano composites have significant potential in diverse engineering applications in weight critical industries, especially such as for automobile sector.