CALPHAD based kinetic Monte Carlo simulation of clustering in binary Al-Cu alloy

A multi-body atomistic model has been developed for precipitation within a FCC substitutional aluminium alloy based upon the CALPHAD thermodynamic databases. Combined with diffusivity data, the model is applied to kinetic Monte Carlo simulation of solute Cu clustering in a binary Al-Cu alloy. Both pairwise and four-body interactions are employed and it is demonstrated that, although limited to next nearest-neighbour distances, the multi-body description results in features that resemble Guinier-Preston (GP) zones. It is not necessary to explicitly introduce long-range elastic interactions to simulate the monatomic planar dimensions, form and crystallography of GP-zones because these effects are inherently captured in the CALPHAD phase descriptions. This result shows that, although long-range interactions are believed to be crucial in the formation of planar features such as GP-zones, first nearest-neighbour multi-body interactions could, in principle, explain their appearance. The model is potentially readily generalised to multi-component alloys.