Phase-field-crystal study of grain boundary premelting and shearing in bcc iron

Ari Adland, Alain Karma, Robert Spatschek, Dorel Buta, and Mark Asta
Phys. Rev. B 87, 024110 – Published 29 January 2013

Abstract

We use the phase-field-crystal (PFC) method to investigate the equilibrium premelting and nonequilibrium shearing behaviors of [001] symmetric tilt grain boundaries (GBs) at high homologous temperature over the complete range of misorientation 0<θ<90 in classical models of bcc Fe. We characterize the dependence of the premelted layer width W as a function of temperature and misorientation. In addition, we compute the thermodynamic disjoining potential whose derivative with respect to W represents the structural force between crystal-melt interfaces due to the spatial overlap of density waves. The disjoining potential is also computed by molecular dynamics (MD) simulations, for quantitative comparison with PFC simulations, and coarse-grained amplitude equations (AE) derived from PFC that provide additional analytical insights. We find that, for GBs over an intermediate range of misorientation (θmin<θ<θmax), W diverges as the melting temperature is approached from below, corresponding to a purely repulsive disjoining potential, while for GBs outside this range (θ<θmin or θmax<θ<90) W remains finite at the melting point. In the latter case, W corresponds to a shallow attractive minimum of the disjoining potential. The misorientation range where W diverges predicted by PFC simulations is much smaller than the range predicted by MD simulations when the small dimensionless parameter ε of the PFC model is matched to liquid structure factor properties. However, it agrees well with MD simulations with a lower ε value chosen to match the ratio of bulk modulus and solid-liquid interfacial free energy, consistent with the amplitude-equation prediction that θmin and 90θmax scale as ε1/2. The incorporation of thermal fluctuations in PFC is found to have a negligible effect on this range. In response to a shear stress parallel to the GB plane, GBs in PFC simulations exhibit coupled motion normal to this plane or sliding. Furthermore, the coupling factor exhibits a discontinuous change as a function of θ that reflects a transition between two coupling modes. Sliding is only observed over a range of misorientation that is a strongly increasing function of temperature for T/TM0.8 and matches roughly the range where W diverges at the melting point. The coupling factor for the two coupling modes is in excellent quantitative agreement with previous theoretical predictions [Cahn, Mishin, and Suzuki, Acta Mater. 54, 4953 (2006)].

  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
19 More
  • Received 26 October 2012

DOI:https://doi.org/10.1103/PhysRevB.87.024110

©2013 American Physical Society

Authors & Affiliations

Ari Adland and Alain Karma

  • Department of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, Massachusetts 02115, USA

Robert Spatschek

  • Max-Planck-Institut für Eisenforschung GmbH, D-40237 Düsseldorf, Germany

Dorel Buta and Mark Asta

  • Department of Materials Science and Engineering, University of California, Berkeley, California, 94720 USA

See Also

Structural short-range forces between solid-melt interfaces

R. Spatschek, A. Adland, and A. Karma
Phys. Rev. B 87, 024109 (2013)

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand
Issue

Vol. 87, Iss. 2 — 1 January 2013

Reuse & Permissions
Access Options
CHORUS

Article Available via CHORUS

Download Accepted Manuscript
Author publication services for translation and copyediting assistance advertisement

Authorization Required


×
×

Images

×

Sign up to receive regular email alerts from Physical Review B

Log In

Cancel
×

Search


Article Lookup

Paste a citation or DOI

Enter a citation
×