Characterization and Mechanical Analysis of Functionally Graded Al-Si₃N₄ Composites through Centrifugal Process

The main objective of this work is the fabrication of functionally graded aluminum ceramic composite (FGACC) using centrifugal casting and to study its physical and mechanical properties. LM6 aluminum alloy and silicon nitride (Si₃N₄) are mixed to form FGACC. This enables the material to have the best of both materials. Si₃N₄ is varied in size of 30 and 3 µm and volume fraction of 8% and 12%. Centrifugal casting was carried out based on L4 orthogonal array. The gradual change in the distribution of reinforcement of the casted FGACC is ensured using optical microscope SEM and hardness. Image Analyser software was used analyze the volume fraction of phase and grain size for all FGACCs. It was observed that the Si₃N₄ concentration increases from the inner to the outer periphery of the casted ring. This is due to the radial forces generated from centrifugal casting to segregate a second discrete phase from the matrix of composite materials. Rockwell hardness values increased from the inner to the outer region ensuring the gradual increase in Si₃N₄. Hardness increased by 30 and 22% in outer for 3 and 30 µm. Archimedes principle was used to find the density based on which the porosity was calculated. Porosity values were 1.8% in the outer region and 2.97% in the inner region. SEM images were also used to characterize the FGACC. ANOVA was done to find the most influencing parameter on hardness. R² value for the outer region was 99.24%, indicating that the developed model is accurate and fits very well with experimental values.