Reversing Hall-Petch Supplementary Data
Description
This dataset demonstrates the compelling story that the same GB functions as a strong obstacle to GB transmission giving rise to HP behavior but then also provides the genesis for IHP behavior through the formation of glissile GBDs that cause GB migration (non-HP deformation) at much lower stresses in the single dislocation regime. Further, this research offers strong evidence that the dislocation pile-up model, which naturally gives rise to HP physics, is also able to provide a simple explanation for IHP behavior by transitioning in a natural manner from GB transmission to GB sliding and migration.
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Steps to reproduce
2D bicrystal atomistic models were constructed as previously described [1-3]. Periodic boundary conditions are applied perpendicular to the normal direction of the GB plane. Straight dislocations are introduced into the upper grain, the model is strained, and the dislocation is quasi-statically pushed into the GB with gradually increasing applied stress followed by 5.6 ps of MD at 0K after each strain increment. EAM interatomic potentials for Al, Cu, and Ni were used [2, 4] and the MD model has xy dimensions of 50(0.5a√(22)) nm by 20nm (~20000 atoms), where a is the lattice parameter . The coordinate system is x-axis parallel to the {323}-direction, y-axis parallel to the {131}-direction, and the z-axis is [101] out of the plane of the figure. The dislocation with line direction parallel to the <110>-tilt axis is dislocation CA=a/2[01 ̅1], which is placed in the upper grain within a few lattice spacings of the boundary plane. The outgoing dislocation in the lower grain is dislocation BA=a/2 [11 ̅0]. Controlled shear deformation of the model to force the CAU dislocation through the GB was produced using a 3x3 displacement gradient tensor that was constructed from the 9x9 matrix after rotation into upper and lower grain coordinate systems as described on p. 35ff in Hirth and Lothe [6]. Dislocation glide forces were computed using the Peach-Koehler (PK) relation as Eq. 3-91 of Hirth and Lothe [6]. We created a series of strain tensors where ϵ_23 was systematically varied from ±60 MPa per strain step at the extremes while the glide force on CAU and BAL remained constant. [1] M. de Koning, R.J. Kurtz, V.V. Bulatov, C.H. Henager, R.G. Hoagland, W. Cai, M. Nomura, Modeling of dislocation-grain boundary interactions in FCC metals, Journal of Nuclear Materials 323(2-3) (2003) 281-289. [2] R.J. Kurtz, R.G. Hoagland, J.P. Hirth, Effect of extrinsic grain-boundary defects on grain-boundary sliding resistance, Philosophical Magazine A (Physics of Condensed Matter: Structure, Defects and Mechanical Properties) 79(3) (1999) 665-81. [3] R.J. Kurtz, R.G. Hoagland, J.P. Hirth, Computer Simulation of Extrinsic Grain-Boundary Defects in the S11 <101> {131} Symmetric Tilt Boundary, Philosophical Magazine A: Physics of Condensed Matter: Structure, Defects and Mechanical Properties 79(3) (1999) 683-703. [4] C.H. Henager Jr, R.J. Kurtz, R.G. Hoagland, Interactions of dislocations with disconnections in fcc metallic nanolayered materials, Philosophical Magazine 84(22) (2004) 2277-2303. [5] R.G. Hoagland, R.J. Kurtz, The relation between grain-boundary structure and sliding resistance, Philosophical Magazine A: Physics of Condensed Matter, Structure, Defects and Mechanical Properties 82(6) (2002) 1073-1092. [6] J.P. Hirth, J. Lothe, Theory of Dislocations, 2nd ed., John Wiley & Sons: New York, New York, 1982.
Institutions
- Pacific Northwest National Laboratory
Categories
Funders
- Office of Basic Energy SciencesUnited States
- Office of Fusion Energy SciencesUnited States