Non-isothermal precipitation kinetics in metallic alloys

Non-isothermal precipitation treatments are studied on two alloys: Al-Zn-Mg and Fe-Cu. In-situ small-angle X-ray scattering experiments provide quantitative measurements of the precipitate characteristics. Class modeling is also performed to compare with experimental results. The transition from metastable to stable precipitates during continuous experiments is shown to critically depend on the heating rate. Reversion treatments are a sensitive tool to study the stability of precipitates; their characteristics are well described by a simple modeling approach, which can be understood in terms of the comparison between the critical radius and the average radius. Finally, a consistent precipitation model is presented. which is capable of describing both isothermal and non-isothermal precipitation processes. The combined use of both types of experiments is shown to be a useful tool for the determination of physical parameters such as diffusion constants and interfacial energy.