The Effect of Al2O3 Nano Particles on Characteristics of Mg-Al-5TiB Grain Refiner Composites Produced by Stir Casting Method

Abstract

High needs for light material with good mechanical characteristics made magnesium and its alloys as an alternative choice because of magnesium’s low density, 1.74 gr/cm3. However, its use is limited by its low strength and ductility. In this experiment, a fabrication process of the composite which is Mg-Al-5TiB as Matrix with the addition of Nano Al2O3 as a reinforced with volume fraction varied from 0.10 Vf-% to 0.25 Vf-% by stir casting method. The composites then were characterized by both microstructure and mechanical properties. The microstructure was analyzed by an optical microscope and scanning electron microscope link to energy-dispersive spectra to analyze the phases present in composites and confirmed by X-Ray Diffraction. The XRD shows some phases such as Mg, MgO, MgAl2O4, and B2O3. The optimum mechanical properties of composites were obtained at the addition of 0.2 Vf-% Al2O3, where the tensile strength, elongation, wear rate and impact strength were 46.1 MPa, 14%, 0.3x10-5 mm3/s, and 0.06 J/mm2. The hardness of composites was value, 40.1 HRH. The porosity maximum was found at the addition of 0.25 Vf-% with the value of 9.37% caused by nano Al2O3 particle forming clustering (porosity is related to clustered particles) and inhibiting liquid metal moving rate. The addition of grain refiner makes solidification went faster and refined the grains.