LINE DEFECTS Edge 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 DEFECTS Screw 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 DEFECTS Mixed Dislocation  The character of a dislocation may change along its line, however the direction of the Burgers vector remains the same. b b 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. Schematic Adapted from Fig. 4.7, Callister 6e. Adapted from Fig. 4.10, Callister 6e. (Fig 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