Microstructure and sliding wear characterization of submicron and nanometric boron carbide particulate reinforced AA2124 aluminum matrix composites prepared by stir casting

Submicron and Nanometric sized ceramic particles provide an enhanced performance of aluminum matrix composites (AMCs) to that of commonly used micron sized particles. B₄C particles (∼250 nm) were effectively reinforced (0,1,2,3 and 4 wt%) into AA2124 aluminum alloy using conventional stir casting technique using an arrangement to pour the molten metal through an aperture at the bottom. B₄C particles were preheated and small quantity of K₂TiF₆ was added to improve wettability. The microstructure and other details of the cast composites were studied using XRD, FESEM, TEM and EBSD. FESEM micrographs and elemental mapping showed a refinement in dendrite structure and proper dispersion of B₄C particles in the aluminum matrix. EBSD demonstrated a decrease in grain size with increased content of B₄C particles. XRD patterns confirmed the absence of interfacial reaction between aluminum and B₄C particles. TEM micrographs revealed the development of dislocation filled strain fields and reaction free proper bonding of B₄C particles. The addition of B₄C particles provided an improvement in microhardness and wear resistance of the composite.