Improving microstructural and mechanical response of new AZ41 and AZ51 magnesium alloys through simultaneous addition of nano-sized Al 2 O 3 particulates and Ca Md Ershadul Alam a , Abdel Magid Salem Hamouda a,⇑ , Quy Bau Nguyen b , Manoj Gupta b a Department of Mechanical and Industrial Engineering, College of Engineering, Qatar University, Doha 2713, Qatar b Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Singapore article info Article history: Received 29 March 2013 Received in revised form 26 April 2013 Accepted 29 April 2013 Available online 29 May 2013 Keywords: Magnesium alloy Calcium AZ41 AZ51 Nanocomposite abstract In the present study, new magnesium based AZ41/Al 2 O 3 –Ca and AZ51/Al 2 O 3 –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 2 O 3 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 Al 2 O 3 particulates and Ca into AZ41 and AZ51 samples helped to reduce the average grain size and diameter of Mg 17 Al 12 second phase and introduced (Mg, Al) 2 Ca phase in the matrix. Microhardness test results revealed that AZ51/Al 2 O 3 –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 com- mercially available Mg alloys. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Magnesium, with a density of 1.74 g/cm 3 , is the lightest engi- neering materials available in the earth which is about 35% and 78% lighter than aluminum based (2.70 g/cm 3 ) and iron based (7.87 g/cm 3 ) materials, respectively [1]. Therefore, they are attracting much attention in certain key engineering applications, particularly in automobile and aviation industries due to the increasing demand for the reduction of fuel consumption and green house gas (CO 2 ) emission [2–7]. Aluminum (Al) and zinc (Zn) containing magnesium (Mg) alloys are known as AZ alloys [8–10]. These alloys are easily available, reasonably priced and used in many engineering applications. However, the properties of these alloys can be further improved by reinforcing them [4,6]. This is particularly useful in engineering applications especially when properties of traditional materials like metals, polymers and ceramics are not able to match with expected properties. In re- cent studies, it has been observed that the addition of nano-sized reinforcements such as ceramic oxides, SiC and carbon nanotubes can lead to a simultaneous increase in strength and ductility of magnesium [11–13]. Among all the reinforcements, it can be ob- served from the study that the 1.5 vol.% addition of nano-sized alu- mina particulates in magnesium-based matrix improved ductility and microhardness significantly while affecting strength [4,11]. Open literature search also indicate that the addition of Ca assists in grain refinement, enhancing corrosion and creep resistance as well as improving thermal and mechanical properties of magne- sium based alloys and their composites while ductility is compro- mised [8–10,14–16]. Accordingly, in the present study, new (AZ41, AZ51)/1.5 vol.% Al 2 O 3 –(1 and 2 wt.%) Ca nanocomposites are syn- thesized using disintegrated melt deposition technique followed by hot extrusion. Microstructure and mechanical properties were characterized and role of alumina nano-particulates and calcium was investigated. 2. Experimental procedures 2.1. Materials In the present study, AZ31 magnesium alloy ingots (2.94% Al, 0.87% Zn, 0.57% Mn, 0.0027% Fe, 0.0112% Si, 0.0008% Cu, 0.0005% Ni and balance Mg, supplied by Tokyo Magnesium Company Limited, Japan) were used as a matrix material. The 0925-8388/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jallcom.2013.04.207 ⇑ Corresponding author. Tel.: +974 4493 5445; fax: +974 4403 4301. E-mail address: hamouda@qu.edu.qa (A.M.S. Hamouda). Journal of Alloys and Compounds 574 (2013) 565–572 Contents lists available at SciVerse ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jalcom