Grain Boundary Precipitation and Self-Organization in Two-Phase Alloys Under Irradiation: Phase Field Simulations and Experiments in Al-Sb

The evolution of segregation and precipitation at grain boundaries (GBs) in dilute alloys subjected to ion irradiation is investigated by combining phase field (PF) modeling and experiments. The irradiation conditions and alloy parameters promoting the self-organization of finite-size precipitate structures at GBs are specifically investigated. PF simulations indicate that, in two-phase systems, irradiation may induce segregation and precipitation at GBs when point-defect solute drag exceeds back thermal diffusion and irradiation atomic mixing. Fast solute diffusion along GBs promotes GB precipitate coarsening, and it is thus detrimental to the dimensional stability of GB precipitates. Experimental evaluation was performed on Al-1.5 at%. Sb thin films subjected to 2-MeV Ti irradiation at room temperature and at 75°C for doses up to 10 dpa. Characterization by transmission electron microscopy (TEM), scanning TEM, and atom probe tomography indicate that ordered AlSb nanoprecipitates formed at GBs and triple junctions, as well as inside larger grains, during the 75°C irradiation. The stability of these precipitates as well as the role of GB character on GB nanoprecipitation is discussed.