Chemistry, bonding and fracture of grain boundaries in Ni 3Si

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The chemistry and electronic structure at grain boundaries in B-free and B-doped Ni23 at.% Si alloys were examined, with energy dispersive X-ray spectroscopy (EDX) providing information on the former and electron energy loss spectroscopy (EELS) on the latter. Ni-enrichment was seen at large angle boundaries, both in the absence and presence of B. EELS of the Ni L 3 edge showed that the bonding at Ni-rich grain boundaries was similar in both undoped and doped alloys. Comparison of the Ni L 3 edge recorded at the grain boundary and in the bulk suggests that reduced hybridization and weaker bonding occurs at Ni-rich grain boundaries in both doped and undoped alloys. These changes in bonding are interpreted in terms of changes in the cohesive energy of the boundaries. The relationship between the cohesive energy of grain boundaries and the fracture mode of Ni 3Si is discussed.