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

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146 • Chapter 5 / Imperfections in Solids



b Figure 5.13 Demonstration of how a tilt boundary

having an angle of misorientationθresults from an

alignment of edge dislocations.

Phase Boundaries

Phase boundariesexist in multiphase materials (Section 10.3), wherein a different

phase exists on each side of the boundary; furthermore, each of the constituent

phases has its own distinctive physical and/or chemical characteristics. As we shall

see in subsequent chapters, phase boundaries play an important role in determining

the mechanical characteristics of some multiphase metal alloys.

Twin Boundaries

Atwin boundaryis a special type of grain boundary across which there is a specific

mirror lattice symmetry; that is, atoms on one side of the boundary are located in

mirror-image positions of the atoms on the other side (Figure 5.14). The region

Twin plane (boundary) Figure 5.14 Schematic diagram

showing a twin plane or boundary

and the adjacent atom positions

(colored circles).