Abstract
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.
Highlights
In order to meet the demands of the aerospace, automotive and military industries, the necessity of lightweight and highperformance structural materials has been provided
It is proven that the addition of grain refiners acted as the main strengthening medium to the alloy
Highest value is been proved by Al-Si-TiB2-Sc-Sr, which is 96 Hv, while Al-Si alloy showed the lowest value which is 69 Hv
Summary
In order to meet the demands of the aerospace, automotive and military industries, the necessity of lightweight and highperformance structural materials has been provided. Huge applications of aluminium (Al) based alloy had been favourable due to its outstanding properties especially by adding grain refiner that will intensify the performance [2]. Good features of alloy lead to high demands from industries, which can be achieved by producing more ultrafine grain size This had been done by adding Sc and Sr as the nucleating agents during solidification process to control the morphology changes of the eutectic phase [4]. Previous study by Ibrahim et al, [6] found that the microstructure of Al-Si with TiB2 had much finer microstructure compared to unfine Al-Si alloy It showed that the eutectic silicon microstructure in Al-Si alloy changed from needle-like or acicular to fine grain size or globular when TiB2 is added. Testing on the hardness and tensile properties involved by using Vicker Hardness tester and Instron tensile machine
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