A Multi-Layered Approach to High-Performance Al-Based FGCs: Investigating the Role of Mono and Hybrid Si3N4 and Granite Reinforcements

Abstract This research utilized powder metallurgy technology to create three layers of functionally graded composites (FGCs) based on aluminum alloy (Al6061). It is enhanced with mono and hybrid ceramics, specifically silicon nitride (Si 3 N 4 ) and granite waste. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) were employed to examine the microstructure of the produced FGC powder layers and the sintered samples. Subsequently, the sintered composites' physical, thermal, tribological, and mechanical properties were investigated. The results indicated that incorporating mono and hybrid ceramics positively influenced the refinement of milled powder, reducing the particle size of the Al6061 alloy from 79.18 nm to 36.43 nm, which represents a decrease of approximately 54.39% after reinforcement with 2.5% granite + 5% Si 3 N 4 . Furthermore, both mechanical and tribological properties showed significant improvement. The highly reinforced sample (FGC6), which comprised 1.25% granite + 2.5% Si 3 N 4 in the second layer and 2.5% granite + 5% Si 3 N 4 in the third layer, the compressive strength, Young's modulus, and wear rate improved by about 26.13%, 13.66%, and 16.19%, respectively, compared to the sample without reinforcements (FGC1). Notably, the coefficient of thermal expansion (CTE) for FGC6 samples decreased to 15.1 × 10 –6 /°C, an increase of approximately 35.15% compared to the FGC1 sample (23.3 × 10 –6 /°C). Finally, the addition of reinforcements to the layers harmed the thermal conductivity of the FGC layers.