Insights into dislocation climb efficiency in FCC metals from atomistic simulations
A Abu-Odeh and M Cottura and M Asta, ACTA MATERIALIA, 193, 172-181 (2020).
Dislocation climb is a mechanism fundamental to high temperature deformation processes, annealing of quenched-in defects, and irradiated defect absorption in metals. It is known from experimental observations and theoretical considerations that climb velocities in face-centered- cubic (FCC) metals can be slower than expected from diffusion kinetics, due to limited jog availability. Here we investigate the so-called climb efficiency, i.e., the ratio of the steady state climb velocity to that expected from diffusion-limited rates, employing atomistic simulations for FCC metals within the framework of a previously developed analytical model. The simulations consider the energetics of jog-pair formation and vacancy migration in the vicinities of edge-dislocations in Al and Cu. Calculated climb efficiencies for the lower-stacking-fault-energy Cu system are found to be substantially lower than those for Al over a wide range of homologous temperatures. These results agree qualitatively with experimental observations showing that the dislocation climb efficiency in FCC materials tends to be lower in systems with smaller stacking fault energy. Considerably higher energies and more complex kinetic pathways are reported for jog-pair formation in Cu than in Al, which correlates with the larger dissociation distance between partial dislocations in this system. This work highlights how atomistic modeling can be used to enhance mesoscale models of climb, and suggests alloy design considerations to tune climb efficiencies. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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