Callister - An introduction - 8th edition

116 • Chapter 4 / Imperfections in Solids
• A scanning probe microscope employs a small and sharp-tipped probe that rasterscans
the specimen surface. Out-of-plane deflections of the probe result from
interactions with surface atoms. A computer-generated and three-dimensional
image of the surface results having nanometer resolution.
Grain Size Determination
• With the intercept method, used to measure grain size, a series of straight-line
segments (all having the same length) are drawn on a photomicrograph. Line
length is divided by the average number of grain intersections on a per-line basis.
Average grain diameter is taken as this result divided by the magnification of the
photomicrograph.
• Comparison of a photomicrograph (taken at a magnification of 100) with ASTM
standard comparison charts may be used to specify grain size in terms of a grain
size number.
• The average number of grains per square inch at a magnification of 100 is related
to grain size number according to Equation 4.16.
Equation Summary
Equation
Page
Number Equation Solving For Number
4.1 N y N exp a Q y
Number of vacancies per unit volume 92
kT b
4.2 N N Ar
Number of atomic sites per unit volume 93
A
4.3 C 1 m 1
100 Composition in weight percent 95
m 1 m 2
n m1
4.5 C¿ 1
100 Composition in atom percent 96
n m1 n m2
C 1 A 2
4.6a C¿ 1
100 Conversion from weight percent to atom percent 96
C 1 A 2 C 2 A 1
C¿ 1 A 1
4.7a C 1
100 Conversion from atom percent to weight percent 96
C¿ 1 A 1 C¿ 2 A 2
C 1
C–
4.9a 1
° C 1
Conversion from weight percent to mass per unit volume 97
C 2 ¢ 103
r 1 r 2
r ave 100
4.10a C 1
Average density of a two-component alloy 97
C 2
r 1
r 2
A ave 100
4.11a C 1
Average atomic weight of a two-component alloy 97
C 2
A 1
A 2
4.16 N 2 n1
Number of grains per in. 2 at 100 magnification 113