WEB Precipitation under Strong Chemo-mechanical Coupling EffectsWednesday (01.01.2020) 00:00 - 00:15 Part of:
A fine dispersion of small precipitates is one of the main strengthening mechanisms in metallic systems. The size and distribution of the precipitates are time-dependent properties strongly affected by solute redistribution as well as the stress state within the matrix. Extensive studies have been devoted to investigating growth and ripening of precipitates considering interfacial, chemical and mechanical driving forces. In a series of studies, we have extended the actual considerations of growth and ripening phenomena by introducing a cross-coupling of chemical and mechanical states of the system. Here we present combined theoretical and experimental works to explore precipitation of δ', θ' and T_1 phases in Al-Li and Al-Cu-Li systems. Theory of growth and ripening under chemo-mechanical coupling has been developed. By combining phase-field simulations and in-situ TEM studies, the first evidence of an inverse ripening mechanism has been revealed in the case of δ' precipitates. For the θ' and T_1 precipitates, it was shown that the stress state around the precipitates can have profound effects on the diffusion-controlled growth and ripening. Long-term annealing investigations revealed that the thickening of the T_1 precipitates is influenced by cross-coupling of stress and diffusion states. The application of these findings in designing precipitation-hardened alloy systems will be discussed.