Fundamentals of Materials Science and Engineering: An Integrated Approach, 3e

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5.7 Dislocations—Linear Defects • 143

(a)

(b)

b

b

B

C

A

B

b

A b

C

b

Figure 5.10 (a) Schematic representation of a dislocation that has edge, screw, and mixed

character. (b) Top view, where open circles denote atom positions above the slip plane. Solid

circles are atom positions below. At pointA, the dislocation is pure screw, while at pointB,it

is pure edge. For regions in between where there is curvature in the dislocation line, the

character is mixed edge and screw. [Figure (b) from W. T. Read, Jr.,Dislocations in Crystals,

McGraw-Hill Book Company, New York, 1953.]