Microstructural analysis of network-like crack structure formed at Al–B4C interface

• Published in: Journal of the European Ceramic Society 2021-11, Vol.41 (14), p.6962-6970
• Main Authors: Gou, Roujia, Yamashita, Seiji, Sekine, Kiyoto, Kita, Hideki
• Format: Article
• Language: English
• Subjects: Aluminium penetration; Boron carbide; Joint; Microcrack; Network structure
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/j.jeurceramsoc.2021.06.043

•In this study, the shape of the aluminium after penetration and the morphology of the cracks can be easily observed.•The molten aluminium fills the narrow cracks and forms a network.•Although Al reacts with B4C in the main junction, no aluminium compounds are found in the microcracks.•Capillarity and changes in chemical energy were taken into account simultaneously. The morphology and structure of microcracks extending toward B4C were investigated from a joint obtained by sandwiching Al foil between two B4C ceramic plates and heat-treating at 1000 °C in vacuum. Network-like structures of cracks were seen, and Al penetrated the extremely narrow part at the tip. The molten Al penetrated a narrow area within the cracks and filled them. Several compounds were produced in the primary junction area because of reactions between Al and B4C. However, only pure Al was present within the cracks. Atoms moved easily in a wide joint interface, and a reaction occurred accordingly, whereas in a narrow region inside the micro crack, atoms moved with difficulty even if molten Al penetrated the crack. The fact that the reaction is unlikely to occur inside the crack is consistent with the permeation of Al into the inside of the elongated crack.