Development of A356-TiB₂ In-Situ Nanocomposite Brake Disc via Intensive High Shear Mixing and Vertical Centrifugal Casting Techniques

Aluminum alloy A356-xTiB₂ (x = 1, 2, 3, 4 wt%) in-situ nanocomposite brake discs were fabricated using a flux-assisted synthesis process, coupled with intensive high-shear (HS) mixing and vertical centrifugal casting techniques. The microstructure of the nanocomposites, along with the size and distribution of in-situ TiB₂ particles within the brake disc was characterized using an optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The nanocomposites exhibited fine α-Al phases, eutectic Si needles and clusters of TiB₂ particles. The addition of TiB₂ particles changed the dendritic structure of the α-Al phase into the cellular structure. The TEM analysis confirmed the presence of nano-sized TiB₂ particles and their clusters within the matrix and eutectic regions. Notably, there were no significant variations in the volume fraction of TiB₂ from the inner to outer regions of the disc. As a result, a slight decrease in the hardness was noticed from the outer to inner periphery along the radial direction of the disc. Tensile and compressive strength was increased with TiB₂ content upto 3 wt%, similarly trend was observed in the wear rate of the composites. However, a decrease in mechanical properties was observed in the 4 wt% TiB2 composites, likely due to the presence of large TiB2 agglomerates and their debonding from the matrix during the testing.