Thermodynamic model for lattice point defect-mediated semi-coherent precipitation in alloys

Maylise Nastar (1) , Lisa Belkacemi (1) , Estelle Meslin (1) , Marie Loyer-Prost (1)

1 SRMP - Service de recherches de métallurgie physique

The formation of precipitates with an atomic volume different from their parent phase eventually leads to a loss of the lattice continuity at the matrix/precipitate interface. Here, we show the creation or removal of lattice sites mediated by lattice point defects is an accommodation mechanism of the coherency loss and even a precipitation driving force. We introduce a thermodynamic approach that rationalizes the selection of phases resulting from chemical and crystallographic constraints in relation to point defect properties. The resulting semi-coherent phase diagram and the precipitation kinetic model depend on the equilibrium phase diagram, the eigenstrain of the precipitating phase, and the chemical potential of point defects. From a joint experimental and modeling study, we uncover the prominent role of excess point defects in unforeseen phase transformations of the Fe-Ni metallic system under irradiation. By addressing the fundamental role of lattice point defects in the accommodation mechanisms of precipitation, we provide a step torwards the understanding of semi-coherent phase transformations occurring in solid materials upon synthesis and in use.

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Maylise Nastar, Lisa Belkacemi, Estelle Meslin, Marie Loyer-Prost. Thermodynamic model for lattice point defect-mediated semi-coherent precipitation in alloys. Communications Materials, 2021, 2, pp.32. ⟨10.1038/s43246-021-00136-z⟩. ⟨cea-03467616⟩