Differential effects of Si/dpa ratio on the evolution of dislocation loops in Al-2.64 Mg alloy during in-situ irradiation

Abstract

Transmutated Si element is an important issue in the neutron irradiation of Al alloys. The Si production per dpa has been noticed to vary with the neutron energy spectrum, but the effect of Si/dpa ratio on the dislocation loop evolution has been rarely studied. In this work, the effect of Si/dpa ratio in Al-2.64 Mg alloy is in-situ quantitatively investigated by Si⁺ irradiation at 100 °C with 1665, 468, and 57 appm/dpa. The higher the Si/dpa ratio, the smaller the loop size, but the higher the loop density in the matrix, which can be attributed to the high Si/dpa ratio leading to more lattice distortion and nucleation sites. Dislocation loops are preferentially formed around Al₉Fe_2-xNi_x precipitates due to the lattice mismatch at the interface. This phenomenon is more obvious at the low Si/dpa ratio. While Mg₂Si precipitates have less effect on the formation of loops regardless of the Si/dpa ratio, because Al/Mg₂Si interfaces are more likely to form a semi-coherent orientation and only result in mild lattice mismatch. But the type of dislocation loops is not affected by the lattice distortion and mismatch. In general, the Si atoms existed in Al lattice can significantly affect the dislocation loop evolution depending on the Si/dpa ratio. The current Si⁺ irradiation results provide valuable data for understanding the transmutation behavior of Al alloys.