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

GTBL042-05 GTBL042-Callister-v3 September 28, 2007 21:43

2nd Revise Page

140 • Chapter 5 / Imperfections in Solids

Substitution of this expression and itsm′ 2 equivalent into Equation 5.16 gives

C 1 ′=

C 1 M′

100 A 1

C 1 M′

100 A 1

+

C 2 M′

100 A 2

× 100 (5.18)

Upon simplification we have

C 1 ′=

C 1 A 2

C 1 A 2 +C 2 A 1

× 100

which is identical to Equation 5.9a.

EXAMPLE PROBLEM 5.5

Composition Conversion—From Weight Percent to

Atom Percent

Determine the composition, in atom percent, of an alloy that consists of 97 wt%

aluminum and 3 wt% copper.

Solution

If we denote the respective weight percent compositions asCAl=97 and

CCu=3, substitution into Equations 5.9a and 5.9b yields

CAl′ =

CAlACu

CAlACu+CCuAAl

× 100

=

(97)(63.55 g/mol)

(97)(63.55 g/mol)+(3)(26.98 g/mol)

× 100

= 98 .7 at%

and

CCu′ =

CCuAAl

CCuAAl+CAlACu

× 100

=

(3)(26.98 g/mol)

(3)(26.98 g/mol)+(97)(63.55 g/mol)

× 100

= 1 .30 at%

Miscellaneous Imperfections

5.7 DISLOCATIONS—LINEAR DEFECTS

Adislocationis a linear or one-dimensional defect around which some of the atoms

VMSE

Edge

are misaligned. One type of dislocation is represented in Figure 5.8: an extra portion

of a plane of atoms, or half-plane, the edge of which terminates within the crystal.

This is termed anedge dislocation;it is a linear defect that centers around the line that

edge dislocation is defined along the end of the extra half-plane of atoms. This is sometimes termed