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Discovery of multimechanisms of screw dislocation interaction in bcc iron from open-ended saddle point searches

Journal Article · · Physical Review Materials
 [1];  [2];  [2];  [3]
  1. Univ. of Tennessee, Knoxville, TN (United States); OSTI
  2. Stanford Univ., CA (United States)
  3. Univ. of Tennessee, Knoxville, TN (United States)
+ Show Author Affiliations

Dislocation motion and interactions determine mechanical properties in body-centered cubic (bcc) metallic materials. However, studying mechanisms for the screw dislocation interaction is fundamentally challenging since many underlying processes involve mesotimescales and atomistic resolution, currently inaccessible by either experimental techniques or continuum theoretical methods. Here, in this paper, we develop a computational capability based on self-evolving atomistic kinetic Monte Carlo (SEAKMC) to sample the critical events and saddle point energies related to screw dislocations and their junctions. The method is first validated by calculating the stress dependence of Peierls barriers and formation energies of kink pairs and cross-slip kink pairs on a single screw dislocation in bcc iron. Then the method is applied to a binary junction of a pair of intersecting screw dislocations, the structure of which is crucial for low-temperature plastic deformation. We identify three important mechanisms: coplanar cross-slipping, jog-pinning, and a previously unknown unzipping mechanism during the evolution of the binary junction. The mechanisms are then further validated using classical molecular dynamics simulations. The computational capability developed in this paper provides an effective tool to evaluate screw dislocation related thermally activated events in complex stress conditions. The mechanisms discovered in this paper provide critical insights into temperature dependence of the anomalous slip, a breakdown of the Schmidt law, during the plastic deformation in bcc iron and can be generalized to other bcc metals.

Research Organization:
Stanford Univ., CA (United States); Univ. of Tennessee, Knoxville, TN (United States); Univ. of California, Oakland, CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF)
Grant/Contract Number:
SC0010412; SC0019151; AC02-05CH11231
OSTI ID:
2420034
Journal Information:
Physical Review Materials, Journal Name: Physical Review Materials Journal Issue: 12 Vol. 6; ISSN 2475-9953
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English

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Related Subjects

36 MATERIALS SCIENCE
Monte Carlo methods
disclinations &amp; dislocations
metals
molecular dynamics