Phase-field-crystal study of grain boundary premelting and shearing in bcc iron
Journal Article
·
· Physical Review. B, Condensed Matter and Materials Physics
- Northeastern Univ., Boston, MA (United States); Northeastern University
- Northeastern Univ., Boston, MA (United States)
- Max-Planck-Inst. für Eisenforschung GmbH, Dusseldorf (Germany)
- Univ. of California, Berkeley, CA (United States)
Here, 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 90° – θmax 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.
- Research Organization:
- Northeastern Univ., Boston, MA (United States)
- Sponsoring Organization:
- USDOE; USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- AC02-05CH11231; FG02-06ER46282; FG02-07ER46400
- OSTI ID:
- 1906106
- Alternate ID(s):
- OSTI ID: 1101992
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 2 Vol. 87; ISSN 1098-0121
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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