Mechanical properties improvement of cast AZ80 Mg alloy/nano-particles composite via thermomechanical processing

Three different nano-composites with cast past) magnesium alloy matrix and nano-particles reinforcement, including Al2O3, TiO2 and SiC, have been prepared via stir casting method. In order to refine the microstructure and improve the mechanical properties, the monolithic AZ80 as well as AZ80/nano-particles composites were thermomechanically processed employing forward extrusion at 200 degrees C. The obtained microstructures of extruded nano-composites materials indicated significant grain refinement due to the progression of dynamic recrystallization (DRX); however, the extruded monolithic material depicts a typical necklace structure with limited DRX grain. To evaluate the mechanical properties, micro-hardness and tensile tests were conducted. The results showed a remarkable increase in hardness of extruded nano-composites because of adding harder particles along with outstanding grain refinement. Furthermore, tensile tests results indicated a remarkable improvement in yield and ultimate strength as well as room temperature ductility for extruded composites compared with cast AZ80 Mg alloy. Finally, it is concluded that adding SiC nano-particles to the cast AZ80 Mg alloy resulted in the best combination of strength and ductility in comparison with Al2O3 and TiO2 particles. This may be attributed to the homogenous distribution of SiC particles and the lowest level of agglomeration during the extrusion process. (C) 2013 Elsevier B.V. All rights reserved.