Origin of variable propensity for anomalous\nslip in body-centered cubic metals

0563341 - ÚFM 2023 RIV GB eng J - Článek v odborném periodiku
Gröger, Roman
Origin of variable propensity for anomalous
slip in body-centered cubic metals.
Modelling and Simulation in Materials Science and Engineering. Roč. 30, č. 8 (2022), č. článku 085007. ISSN 0965-0393. E-ISSN 1361-651X
Grant CEP: GA ČR(CZ) GA19-23411S
Institucionální podpora: RVO:68081723
Klíčová slova: anomalous slip * junctions * screw dislocations * atomistic simulations * dislocation network
Obor OECD: Condensed matter physics (including formerly solid state physics, supercond.)
Impakt faktor: 1.8, rok: 2022
Způsob publikování: Omezený přístup
https://iopscience.iop.org/article/10.1088/1361-651X/ac9b79

Many transition metals crystalizing in the body-centered cubic (bcc) structure
exhibit anomalous slip on low-stressed {110} planes at low homologous tem peratures, which cannot be reconciled with the Schmid law. Specifically, for
uniaxial loading in the center of the [001] − [011] − [¯111] stereographic tri angle, this is manifested by 1/2[111] and 1/2[1¯1¯1] screw dislocations moving
on low-stressed (0¯11) planes. While the anomalous slip is often attributed
to non-planar cores of 1/2⟨111⟩ screw dislocations or to the tendency for
their networks to glide easily, it remains unclear why it dominates the plastic
deformation in some bcc metals, whereas it is weak or even absent in others.
Using molecular statics simulations at 0 K, we demonstrate that the anomalous
slip in bcc metals is intimately linked with the stability of ⟨100⟩ screw junc tions between two intersecting 1/2⟨111⟩ screw dislocations under stress (for
example, 1/2[111] and 1/2[1¯1¯1] screws giving rise to the [100] junction). Our
atomic-level studies show that in nearly all bcc metals of the 5th and 6th groups
these junctions cannot be broken by the applied stress and the three dislocations
can only move on the common {110} plane (in the above example on the (0¯11)
plane). On the other hand, these junctions are found to be unstable in alkali
metals, tantalum, and iron, where the application of stress results in unzipping
of the two dislocations and their further glide on the planes predicted for isol ated dislocations. These results also suggest that the experimentally observed
increased propensity for the anomalous slip in further stages of plastic deform ation may be explained by reduced curvatures of 1/2⟨111⟩ screw dislocation
in dense networks.
Trvalý link: https://hdl.handle.net/11104/0335331