The assisted nucleation of θ' in AL-CU alloys

To improve understanding of the assistance that individual heterogeneous sites afford nucleation of key strengthening precipitate phases recent studies have refocused attention on the precise nature of the barriers to nucleation. This approach has been applied in the present investigation of the earliest stages of microstructural evolution of indium precipitates and θ' plates in an Al-In binary and Al-Cu-In ternary alloys. Focusing on the identity of preferred nucleation sites and the role of pre-age deformation on subsequent precipitation this work identified that the presence of crystal defects was found to influence subsequent nucleation of In' and therefore the resulting distribution and average particle size of θ' plates, acting as preferred sites for θ' despite the availability of matrix dislocations.