2026 Araujo AA1100 B4C Composite Microstructure

The microstructure of a commercially produced AA1100 aluminum matrix composite reinforced with 25 vol.% B4C particles has been characterized to understand its microstructural heterogeneity and interfacial regions. The objective was to identify the relationship between microstructural features and the Ti-rich phase at the interfaces. Using techniques such as X-ray diffraction and transmission electron microscopy, the study revealed irregular and angular B4C particles with local variations in size, morphology, and spacing, leading to a measured area fraction of 26 ± 6%. The aluminum matrix exhibited grain-size heterogeneity, with finer grains in areas devoid of adjacent B4C sites and coarser grains near particle locations. A distinct Ti-rich interfacial region was found between B4C particles and the aluminum matrix, confirmed by X-ray diffraction revealing crystalline TiB2. Further characterization indicated a type IV(a) N2 adsorption-desorption isotherm with an H3 hysteresis loop, showing mesoporosity associated with slit-like pore formations. Crystallographic texture analysis indicated a decrease in maximum orientation distribution from unreinforced to reinforced material. The implications of these findings for the composite's structural performance and neutron absorption capabilities are discussed.