he Role of Al2O3 Nanoparticles Addition on Characteristic of Al6061 Composite Produced by Stir Casting Process

Aluminium Matrix Composites (AMCs) reinforced with Al2O3 nano particles are widely used for high performance application such as aerospace because aluminium is light weight and alumina has good performance at high temperature. Alumina nano particles is added into molten Al with different volume fraction from 0.2 vf-% to 1.2 vf-% while Mg is used as an external dopant with 10 wt-% to promote wetting between aluminium and Al2O3. The Al alloy was then melted and Mg along with the reinforcement was blended inside the molten metal by stirrier with rotational speed of 500 rpm at 800oC for 2 minutes and degassing with Ar for 4 minutes to remove all of gas in molten Al. The molten composites then was casted into plate and tensile test sample molds. The effect of Al2O3 nano particles on mechanical properties and microstructure of composites was investigated. The optimum tensile strength, hardness and elongation of composite was achieved at additon of 0.2vf-% Al2O3np with the value of 220 MPa, 61 HRB and 5.48% respectivelly. Increasing hardness was caused by impedation of dislocation movements by nano-Al2O3 particles. It is found that the addition of more Al2O3np, the mechanical propeties decreased. The microstructure observations showed that the composites yield finer grains than the unreinforced alloy Addition of nano-Al2O3 particles also tend to form microporosity and agglomeration which would decrease the tensile strength of composites.