Effects of temperature on surface-controlled dislocation multiplication in body-centered-cubic metal nanowires
G Song and SW Lee, COMPUTATIONAL MATERIALS SCIENCE, 168, 172-179 (2019).
Recent computational studies revealed that screw dislocations in body- centered-cubic (bcc) metal nanowires can self-multiply through cross- slip near the free surface. This unique process was termed surface- controlled dislocation multiplication (SCDM). In bcc metals, screw dislocation motion and its cross-slip behavior are often related to thermally activated processes; due to this relation, SCDM is expected to be highly temperature-sensitive. In this study, therefore, we investigated how temperature influences the SCDM in bcc molybdenum and niobium nanowires using atomistic simulations. Regardless of the difference in lattice resistance at a given temperature, both systems show similar trends of critical shear stress of SCDM with respect to temperature. The temperature dependence was found to be divided into three different regimes; (1) lattice-resistance-dominant; (2) segmentation-dominant; (3) steady-state segmentation. The presence of these three regimes will be discussed in terms of the temperature- dependence of the lattice resistance and the dynamics of dislocation segmentation in the nano-scale volume. Our results provide a fundamental understanding of screw dislocation behavior in bcc metals at the nanometer scale and varying temperatures.
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