Effect of nano-Al2O3 addition and heat treatment on the microstructure and mechanical properties of Mg-(5.6Ti+3Al) composite

Abstract

Abstract In this study, the independent and synergic effects of nano-Al2O3 addition and heat treatment on the microstructure and mechanical properties of Mg-(5.6Ti + 3Al) composite were investigated. The addition of nano-Al2O3 particles to Mg-(5.6Ti + 3Al) was carried out in two ways: (i) direct addition to Mg along with ball milled (Ti + Al) particulates, to form Mg-(5.6Ti + 3Al)-2.5Al2O3 composite and (ii) addition after ball milling together with Ti and Al, to form Mg-(5.6Ti + 3Al + 2.5Al2O3) composite. The materials were synthesized through the disintegrated melt deposition technique followed by hot extrusion, and were investigated for their microstructure and mechanical properties. Results indicate that the final microstructure and mechanical properties of Mg composites were greatly influenced by the mode of nano-Al2O3 addition and heat treatment. While the direct addition of nano-Al2O3 particulates caused improvement in fracture strain without affecting the strength properties, its addition after ball milling resulted in lowering the strength properties without significant effect on the ductility. The improvement in ductility without affecting the strength values in the case of Mg-(5.6Ti + 3Al)-2.5Al2O3 composite is attributed to the presence of nano-Al2O3 particulates and Al3Ti intermetallics in Mg matrix. The heat treatment of all the composites at 200 °C for 5 h leads to a significant enhancement in ductility with slight reductions in strength values, under both tensile and compressive loading conditions. This is attributed to the stress relaxation at matrix–reinforcement interface. The best combination of strength and ductility was obtained after heat treatment of the extruded composites.