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LINE DEFECTSEdge Dislocation
Burgers vector
slipped
Dislocation Line
Dislocation “core”
A dislocation is define by its line and its displacement vector known as Burgers vector.
Dislocation line is the boundary between the slipped and un-slipped areas.
The dislocation line is perpendicular to the Burgers vector in edge dislocations.
Un-slipped
Adapted from “Engineering Materials 1” by Ashby and Jones
LINE DEFECTSScrew Dislocation
Dislocation line
cut
displace
The dislocation line is parallel to the Burgers vector in screw dislocations
Adapted from “Engineering Materials 1” by Ashby and Jones
LINE DEFECTSMixed Dislocation
The character of a dislocation may change along its line, however the direction of the Burgers vector remains the same.
bb
Adapted from Figure 4.5 of Callister
Observing Dislocations
Transmission Electron Microscopy (TEM) Etch Pitting
Copper
High Resolution TEM
Other techniques:- X-ray- Field Ion Microscopy
Grain boundaries: • are boundaries between crystals. • have a change in crystal orientation across them. • form by many processes including solidification, deposition and recrystallization.
grain boundaries
Schematic
Adapted from Fig. 4.7, Callister 6e. Adapted from Fig. 4.10, Callister 6e. (Fig. 4.10 is from Metals Handbook, Vol. 9, 9th edition, Metallography and Microstructures, Am. Society for Metals, Metals Park, OH, 1985.)
Metal Ingot
AREA (PLANAR) DEFECTS: GRAIN BOUNDARIES
~ 8cm
heat flow
OBSERVING GRAIN BOUNDARIES
Optical Microscopy HRTEM
Low-angle boundary
Nanocrystalline Ni-15%Fe alloy
Adapted from Callister, Fig. 4-12
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