Synthesis of aluminium (Al) and alumina (Al2O3)-based graded material by gravity casting

In the present work, aluminium alloy-based composites were developed for automobile applications. Aluminium-based functionally graded material (FGM) was developed by adding 2.5, 5 and 7.5 wt% of nanoparticles of alumina. The composites were made using gravity casting in an open hearth furnace with the surface temperature of FGM maintained at 750, 850 and 1,000°C. The microstructure of the samples was studied using scanning electron microscopy and particle distribution. The particle distribution was higher at the bottom in all compositions, which can be attributed to more solidification time. As the wt% of the Al2O3 increased, the volume fraction of particles also increased from the top surface to the bottom surface of the samples. After adding 7.5 wt% of Al2O3 and heating up to 1,000°C led to the grain refinement of the alloy. The increase in hardness from the top surface to the bottom surface of the sample verified the development of FGM. Due to increase in the solidification temperature, better reinforcement was observed in the developed FGM.