Cu-15 Ni-3 Al alloys with different dimensions

and different L1

2

phase morphologies and distributions were prepared by solid solution-aging treatment

and the formation of continuous and discontinuous precipitation phase regions in the alloy was explained by thermodynamic analysis and CALPHAD method. The results indicate that in the region close to the grain boundary

partial L1

2

phase is attached to the grain boundary and nucleated during the solid solution stage

thus beginning to grow in the early aging stage

eventually leading to the formation of discontinuous precipitation region. At lower temperatures

the L1

2

phase has a greater driving force for nucleation due to the higher supersaturation and excessive Gibbs free energy of the system

which is precipitated from the matrix through continuous precipitate decomposition

resulting in the formation of a continuous precipitation phase region.