Defect character at grain boundary facet junctions: Analysis of an asymmetric Σ = 5 grain boundary in Fe

Journal Article · Wed Feb 01 00:00:00 EST 2017 · Acta Materialia

DOI:https://doi.org/10.1016/j.actamat.2016.11.017· OSTI ID:1393693

Medlin, D. L.; Hattar, K.; Zimmerman, J. A.; Abdeljawad, F.; Foiles, S. M.

Grain boundaries often develop faceted morphologies in systems for which the interfacial free energy depends on the boundary inclination. Although the mesoscale thermodynamic basis for such morphological evolution has been extensively studied, the influence of line defects, such as secondary grain boundary dislocations, on the facet configurations has not been thoroughly explored. In this paper, through a combination of atomistic simulations and electron microscopic observations, we examine in detail the structure of an asymmetric Σ = 5 [001] grain boundary in well-annealed, body-centered cubic (BCC) Fe. The observed boundary forms with a hill-and-valley morphology composed of nanoscale {310} and {210} facets. Our analysis clarifies the atomic structure of the {310}/{210} facet junctions and identifies the presence of an array of secondary grain boundary dislocations that are localized to these junctions. Analysis of the Burgers vectors of the grain boundary dislocations, which are of type (1/5)<310> and (1/5)<120>, shows that the defect density is consistent with that required to accommodate a small observed angular deviation from the exact Σ = 5 orientation relationship. As a result, these observations and analysis suggest a crucial role for secondary grain boundary dislocations in dictating the length-scale of grain boundary facets, a consideration which has not been included in prior analyses of facet evolution and equilibrium facet length.

• Research Organization: Sandia National Lab. (SNL-CA), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC04-94AL85000
• OSTI ID: 1393693
• Alternate ID(s): OSTI ID: 1333718
• Report Number(s): SAND-2016-11870J; S1359645416308758; PII: S1359645416308758
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Vol. 124 Journal Issue: C; ISSN 1359-6454
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
grain-boundaries
dislocations
faceting
electron microscopy
atomistic modeling