In this study, a functionally graded composite with lightweight and high strength characteristics is produced using an Al-based matrix and hybrid reinforcement via the powder metallurgy route. The effects of carbon nano-tubes (CNTs), Y2O3 and SiC reinforcements in Al matrix have been studied on the structure, morphology, phase composition, thermal stability and mechanical properties. A 3 layered graded bulk sample is fabricated through the powder metallurgy (PM) route using spark plasma sintering (SPS), with Y2O3 content continuously varied from 0 to 1 wt.%. The fabricated sample is characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and indentation techniques.

To achieve a uniform distribution of reinforcements and reduce agglomeration, the milling time is extended to more than 20 hours. This extended milling time effectively cleaves the nanotubes and reduces entanglements. The XRD analysis shows minimal reaction products that are formed during hot processing. Broadening of diffraction peaks suggests induced strain and reduction in crystallite size. SEM–BSE image also shows that the graded structure established from powder mixtures is maintained even after sintering. The incorporation of hybrid reinforcement in the composite has led to a notable improvement in mechanical properties, with the highest Y2O3-containing layer exhibiting a maximum yield strength of approximately 621 MPa. The graded layers in the composite have effectively addressed the coefficient of thermal expansion (CTE) concerns commonly associated with conventional Al-based metal matrix composites (MMCs).

Furthermore, efforts have been made to explore the relationship between the structure and properties of these hybrid composites, as well as conduct interfacial studies. By investigating the structure-property correlation and examining the interfaces, a deeper understanding of the composite's performance and behaviour is studied.