Grain Boundary Properties: Energy (L21) - Materials Science and ...

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28 Grain Boundary Energy • First categorization of boundary type is into low-angle versus high-angle boundaries. Typical value in cubic materials is 15° for the misorientation angle. • Typical values of g.b. energies vary from 0.32 J.m -2 for Al to 0.87 for Ni J.m -2 (related to bond strength, which is related to melting point). • Read-Shockley model describes the energy variation with angle for low-angle boundaries successfully in many experimental cases, based on a dislocation structure.
29 Read-Shockley model • Start with a symmetric tilt boundary composed of a wall of infinitely straight, parallel edge dislocations (e.g. based on a 100, 111 or 110 rotation axis with the planes symmetrically disposed). • Dislocation density (L -1 ) given by: 1/D = 2sin(θ/2)/b ≈ θ/b for small angles.
Page 1 and 2: 1 Carnegie Mellon MRSEC Grain Bound
Page 3 and 4: 3 Outline • Motivation, examples
Page 5 and 6: 5 Properties, phenomena of interest
Page 7 and 8: 7 • Grain boundary sliding should
Page 9 and 10: 9 Measurement of GB Energy • We n
Page 11 and 12: 11 Zero-creep Method • The zero-c
Page 13 and 14: 13 Definition of Dihedral Angle •
Page 15 and 16: 15 Unequal energies • If the inte
Page 17 and 18: 17 Wetting • For a large enough r
Page 19 and 20: 19 Triple Junction Quantities • G
Page 21 and 22: 21 Derivation of Herring Equs. A vi
Page 23 and 24: 23 γ S2 Analysis of Thermal Groove
Page 25 and 26: Bi impurities in Ni have the opposi
Page 27: 27 Grain boundary energy: current s
Page 31 and 32: 31 Read-Shockley contd. • For an
Page 33 and 34: 33 Read-Shockley contd. • If the
Page 35 and 36: 35 Exptl. vs. Computed E gb Tilts
Page 37 and 38: 37 2 i i+2 r ij1 l’ ij j 1 j 3 r
Page 39 and 40: 39 Tilt versus Twist Boundaries Iso
Page 41 and 42: 41 λ(Δg, n) λ(n|5°/[100]) λ(n|
Page 43 and 44: 43 For all grain boundaries in MgO
Page 45 and 46: 45 Symmetric [110] tilt boundaries
Page 47 and 48: 47 Inclination Dependence • Inter
Page 49 and 50: 49 The torque term Change in inclin
Page 51 and 52: 51 Herring’s Relations
Page 53 and 54: 53 Aluminum foil, cross section •
Page 55 and 56: 55 How to Measure Dihedral Angles a
Page 57 and 58: 57 Calculation of G.B. Energy • I
Page 60 and 61: 60 3 ⎪⎪⎧⎧ ∑ ⎨⎨σ ˆ j
Page 62 and 63: 62 Grain Boundary Energy Calculatio
Page 64 and 65: 64 # of total TJs : 8694 # of {111}
Page 66 and 67: 66 Capillarity Vector • The capil
Page 68 and 69: 68 Capillarity vector definition
Page 71 and 72: 71 Computer Simulation of Grain Gro
Page 73 and 74: 73 • Steady state population deve
Page 75 and 76: 75 G.B. Energy: Summary • For low
Page 77 and 78: 77 Supplemental Slides
Page 79:
79 Expanded Young Equations • Pro
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Grain Boundary Properties: Energy (L21) - Materials Science and ...

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