Screw dislocation cross slip at cross-slip plane jogs and screw dipole annihilation in FCC Cu and Ni investigated via atomistic simulations
SI Rao and DM Dimiduk and JA El-Awady and TA Parthasarathy and MD Uchic and C Woodward, ACTA MATERIALIA, 101, 10-15 (2015).
Using atomistic simulations, the effect of jogs on the cross-slip of screw character dislocations and screw-dipole annihilation was examined for both FCC Cu and Ni. The stress-free activation energy for cross-slip at jogs is close to 0.4 eV in Cu, determined using a nudged elastic band method. This value is a factor of 4- to-5 lower than the activation energy for cross-slip of screw dislocations in the absence of a jog. Similar results were obtained for Ni. Molecular dynamics simulations were used to study the annihilation of a jog-containing screw dipole. The critical Escaig stress on the glide plane for dipole annihilation drops quickly from the 0 K value of similar to 400 MPa and, dipole annihilation is nearly athermal at room temperature. At 5 K, Escaig stresses on the cross-slip plane are a factor of 1.5 less effective than Escaig stresses on the glide plane and, glide stresses on the cross-slip plane are a factor of 3 less effective for dipole annihilation by cross- slip. The activation volume for cross-slip of screw dislocations at jogs with respect to these three stress components range from 6 to 20b(3). These results have been found to be useful in physics-based modeling of bulk cross-slip in higher length scale 3D dislocation dynamics simulations investigating dislocation pattern formation and fatigue structures in FCC crystals. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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