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

GTBL042-06 GTBL042-Callister-v3 September 28, 2007 21:46

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6.5 Factors That Influence Diffusion • 173

1500 1200 1000 800 600 500 400 300

Diffusion coefficient (m

2 /s)

10 –8

10 –10

10 –12

10 –14

10 –16

10 –18

10 –20

Temperature (°C)

Reciprocal temperature (1000/K)

0.5 1.0 1.5 2.0

Al in Al

Zn in Cu

Cu in Cu

C in –Fe

Fe in –Fe

C in –Fe

Fe in –Fe

Figure 6.7 Plot of

the logarithm of the

diffusion coefficient

versus the reciprocal

of absolute

temperature for

several metals. [Data

taken from E. A.

Brandes and G. B.

Brook (Editors),

Smithells Metals

Reference Book,7th

edition, Butterworth-

Heinemann, Oxford,

1992.]

Concept Check 6.1

Rank the magnitudes of the diffusion coefficients from greatest to least for the fol-

lowing systems:

NinFeat700◦C

Cr in Fe at 700◦C

NinFeat900◦C

Cr in Fe at 900◦C

Now justify this ranking. (Note: Both Fe and Cr have the BCC crystal structure, and

the atomic radii for Fe, Cr, and N are 0.124, 0.125, and 0.065 nm, respectively. You

may also want to refer to Section 5.4.)

[The answer may be found at http://www.wiley.com/college/callister (Student Companion Site).]

Concept Check 6.2

Consider the self-diffusion of two hypothetical metals A and B. On a schematic graph

of lnDversus 1/T, plot (and label) lines for both metals given thatD 0 (A)>D 0 (B)

and also thatQd(A)>Qd(B).

[The answer may be found at http://www.wiley.com/college/callister Student Companion Site).]