On the growth of Widmanstätten precipitates in an Al–Cu alloy

The formation of intragranular θ′ disk-shaped precipitates in Al–Cu alloys is accompanied by a thickness-dependent misfit strain. In this study, the lengthening rates of Widmanstätten θ′ precipitates of two different thicknesses (1.2 and 2.0 nm) are compared. It is shown experimentally that the thinner precipitates grow more slowly than their 2.0 nm thick counterparts. These observations are interpreted in terms of a model that includes the effects of capillarity and of misfit strain, as well as the effect of a misfitting solute (Cu) in the diffusion field in the parent crystal.