Quantum-mechanically informed model of dynamic precipitation in MgAl alloys

Precipitates are ubiquitous in metallic alloys and play a vital role in strengthening by blocking the motion of dislocations. The size and shape of these precipitates are important. The amount of hardening depends critically on the number density and orientation. Furthermore, they also can contribute to the lack of ductility, fracture and fatigue, and reduced spall strength and creep when their sizes become too large. Therefore, it is of active interest to control the size of these alloys. Unlike precipitates formed due to aging, dynamic (stress induced) precipitation give rise to small precipitate sizes. We present a quantum-mechanically informed strain, concentration and temperature dependent free energy functional for dynamic precipitation in MgAl alloys [1]. We discuss the influence of various conditions of stress and temperature on the microstructure and its consequences.
[1] S. Ghosh and K. Bhattacharya, Acta Materialia, 193, 28-39, July (2020)