A TEM study of radiogenic silicon precipitation in neutron irradiated aluminium

Abstract

Following neutron irradiation of an aluminium component (1080 grade aluminium) from the high flux Australian reactor (HIFAR) to fluences of up to 2.6 × 10 26 thermal neutrons m −2, precipitation of up to 0.64 wt% radiogenic silicon has been observed using TEM. The onset of visible silicon precipitation occurred at 0.2 × 10 26 thermal neutrons m −2. At fluences ⩾1.8 × 10 26 thermal neutrons m −2 diffraction spots due to crystalline silicon were detectable using selected area electron diffraction. This technique showed that the silicon precipitate was predominantly in a cube//cube relationship with the matrix, with twinning observed on the {1 1 1} Si plane. This twinning influenced the shapes of the particles, which exhibited {1 0 0} and {1 1 1} type facets. A second minor orientation relationship (Kobayashi) was also observed.