Dynamic precipitation in Aluminium Alloys: mechanisms and applications – DYNAMITAL

To advance the understanding of these coupled phenomena, DYNAMITAL implemented a quantitative experimental approach, combining controlled mechanical testing with small-angle X-ray scattering measurements, as well as electron microscopy, atom probe tomography, and diffraction. These measurements, conducted in situ during plastic deformation, provide access to the characteristics of hardening nano-precipitates (size, fraction, density) and their evolution, thus quantifying the effect of the main parameters: test temperature, initial state, and strain rate. This quantitative data is then compared with predictive models and helps refine them to achieve predictive control of these processes.

Regarding the first pillar of the project, which focuses on controlling the kinetics of dynamic precipitation under monotonic deformation, the project led to a detailed understanding of the competition between the various physical mechanisms at play. In particular, the leading role of supersaturated vacancies as accelerators of precipitation was highlighted, as well as the dissolution of the smallest precipitates induced by plastic deformation. We demonstrated that the competition between accelerated precipitation and dissolution is controlled by the initial supersaturation level and the thermo-kinetic conditions driven by temperature and strain rate. These mechanisms were implemented in a quantitative model, which predicts microstructural evolutions and maps the dominant mechanisms in the parametric space of processing parameters.

For the second pillar of the project, concerning the kinetics of dynamic precipitation under cyclic deformation, the project determined the strain ranges per cycle required to activate this phenomenon. It also ranked the respective contributions to the final hardening from newly formed precipitates, defects related to cyclic deformation (such as dislocation loops), and other structural defects.

This project resulted in two PhD theses defended in early 2026 by Guillaume Crowin at the SIMAP laboratory and Adam Bouayoune at the MATEIS laboratory. The modeling work was carried out collaboratively between the two PhD students and appears as a common chapter in both theses. The scientific output included 8 conference presentations, and 6 articles are in the process of being published in high-quality international journals (1 submitted at the time of this report).

This project paves the way for predictive control of processes that combine precipitation and plastic deformation, which are widely studied with a view to reducing the weight of automotive and aerospace structures

The aim of the DYNAMITAL project is to gain an in-depth understanding of the mechanisms governing dynamic precipitation in precipitation hardened aluminium alloys, and to explore the potential for new microstructures and properties. In order to predict the competition between acceleration and dissolution of precipitation induced by dynamic effects, and the kinetics of these transformations, the proposed methodology involves particularly in-situ measurements by X-ray scattering. We will conduct a very broad parametric study by studying the effects of temperature, strain rate, initial metallurgical state, supersaturation of alloys as well as the shape of precipitates in relation with the nature of the solute additions. Dynamic precipitation by cyclic deformation will be explored as a means of obtaining microstructures that break away from the usual ones, and the associated properties will be explored.