Aluminium based metal matrix composites (MMCs) have better properties and performance. They are commonly used in transport applications which require combinations of high strength and ductility. They are quite attractive due to their low density, capability to be strengthened by precipitation, good corrosion resistance, high thermal and electrical conductivity. Grain refinement plays a crucial role in improving characteristics and properties of aluminium-silicon (Al-Si) alloy. In this investigation, scandium (Sc) and strontium (Sr) elements were added to aluminium-silicon-titanium diboride (Al-Si-TiB2) alloy for refinement of grains. The compositions of 93 wt.% Al-Si, 6 wt.% TiB2, 0.5 wt.% Sc and 0.5 wt.% Sr were melted into induction furnace. Then the composites have been characterized on the mechanical properties and microstructure characterization. Instron tensile machine and vickers hardness tester were used to characterize the mechanical properties of the composite alloy. Microstructure and phase composition were characterized by Field Emission Scanning Electron Microscope (FESEM) and X-ray Diffraction (XRD). From the results obtained, addition of Sc and Sr, into Al-S-TiB2 improved the tensile strength and hardness of composite alloy. Results also showed that the inoculants addition able to enhance the refinement of grains and escalate the values of hardness and tensile strength of Al-Si-TiB2 composite. Mechanical properties related much on the microstructure as it can be seen that the addition of grain refiners produced much higher value of mechanical properties.

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Aluminium matrix composites by way of in-situ reaction has arisen as a preference conducive to knock out imperfections and defects exiting within ex situ MMC. In the present work, Al-Cu-ZrB2 have been develop through in situ reaction which boost mechanical properties over dispersion strengthening together with grain refinement obtained by the existence of each particulates inside the melt all along solidification. Al-Cu reinforced among different proportion of ZrB2 (0, 3 and 6 wt. %) synthesized using in situ fabrication at 800 °C of molten aluminum-copper alloys by inorganic salts K2ZrF6 together with KBF4. The amalgam were specified using XRD, FESEM together with mechanical test on appropriately sectioned and metallographically prepared surface to examine and inspect phase distribution, hardness together with tensile properties. From result acquired, raised ZrB2 amount will increase rate of tensile and hardness characteristics of Al-Cu alloy. XRD patterns exposed development of ZrB2 particulates without existence of unspecified other compounds. Most of ZrB2 granular were located near grain boundaries of Al dendrites. Microstructural analysis exposed the homogeneous and consistent allocation of second phase particles, clean interface and favorable bonding. It is support that ZrB2 molecules are predominantly in nano size among hexagonal either tetragonal shape, yet minor molecules in micron size are also noticed. For that reason, composite synthesized using in situ techniques exhibit homogeneous distribution of reinforcing tend to be superlative associated within clean interface along the metallic matrix. In order to accomplish better mechanical features, it is necessary to regulate and control phase arrangement all along fabrication of Al-Cu with higher contents of ZrB2.