Formation of the Ni₃₁Si₁₂ phase induced by the irradiation of nickel ions on the eutectic, α-Ni-Ni₃Si-monoclinic, with a 380 dpa dose

This investigation has been developed to determine which microstructural changes on the eutectic α-Ni-Ni₃Si_{- monoclinic}, if any exist, result from the irradiation with Ni-ions. SRIM program has been used to simulate the interaction of the irradiation with both α-Ni and Ni₃Si_{- monoclinic} phases. X-ray diffraction studies of irradiated and non-irradiated regions have allowed us to establish that the ion irradiation promote the formation of the Ni₃₁Si_12-hexagonal intermetallic phase with hexagonal structure. An analysis of the irradiated region by High Resolution Transmission Electron Microscopy (HRTEM) confirmed the presence of the Ni₃₁Si_12-hexagonal intermetallic phase, establishing at the same time, its crystallographic relationship with the matrix. Evidently, radiation-induced segregation could cause significant changes in the chemical composition of concentrated alloys. This experimental discovery, in particular, is significant because the formation of the Ni₃₁Si_12-hexagonal phase under irradiation conditions had never been mentioned before. Nonetheless, the formation of the Ni₃₁Si_12-hexagonal intermetallic phase represents an advance in the field of the microstructural modification by ion beam irradiation, and as a consequence of this finding, it is possible to establish that the structural stability of the eutectic form of the α-Ni-Ni₃Si_-monoclinic phases under severe irradiation conditions, is questionable.