Simulation of the θ′ Precipitation Process with Interfacial Anisotropy Effects in Al-Cu Alloys

The effects of anisotropic interfacial properties and heterogeneous elasticity on the growth and ripening of plate-like theta '-phase (Al2Cu) in Al-1.69 at.% Cu alloy are studied. Multi-phase-field simulations are conducted and discussed in comparison with aging experiments. The precipitate/matrix interface is considered to be anisotropic in terms of its energy and mobility. We find that the additional incorporation of an anisotropic interfacial mobility in conjunction with the elastic anisotropy result in substantially larger aspect ratios of the precipitates closer to the experimental observations. The anisotropy of the interfacial energy shows comparably small effect on the precipitate's aspect ratio but changes the interface's shape at the rim. The effect of the chemo-mechanical coupling, i.e., the composition dependence of the elastic constants, is studied as well. We show that the inverse ripening phenomenon, recently evidenced for delta' precipitates in Al-Li alloys (Park et al. Sci. Rep. 2019, 9, 3981), does not establish for the theta ' precipitates. This is because of the anisotropic stress fields built around the theta ' precipitates, stemming from the precipitate's shape and the interaction among different variants of the theta ' precipitate, that disturb the chemo-mechanical effects. These results show that the chemo-mechanical effects on the precipitation ripening strongly depend on the degree of sphericity and elastic isotropy of the precipitate and matrix phases.

Automated summary

The study investigates the effects of anisotropic interfacial properties and heterogeneous elasticity on the growth and ripening of plate-like theta'-phase in Al-Cu alloy. The results show that anisotropic interfacial mobility and energy significantly affect the aspect ratios of precipitates, while the chemo-mechanical coupling plays a role in the precipitation process. However, the inverse ripening phenomenon observed in another alloy system does not occur for theta'-phase precipitates due to anisotropic stress fields and interactions among different variants.