Page 166 - Materials Science and Engineering An Introduction

138 • Chapter 4 / Imperfections in Solids

Grain-Size Determination
4.45 (a) Using the intercept method determine the
mean intercept length, in millimeters, of the speci-
men whose microstructure is shown in Figure 4.15b;
use at least seven straight-line segments.
(b) Estimate the ASTM grain-size number for
this material.
4.46 (a) Employing the intercept technique, determine
the mean intercept length for the steel specimen
whose microstructure is shown in Figure 9.25a; use
at least seven straight-line segments.
(b) Estimate the ASTM grain-size number for
this material. 150
4.47 For an ASTM grain size of 6, approximately how Determine the following:
many grains would there be per square inch under (a) Mean intercept length
each of the following conditions?
(b) ASTM grain-size number, G
(a) At a magnification of 100
(b) Without any magnification Spreadsheet Problems
4.48 Determine the ASTM grain-size number if 4.1SS Generate a spreadsheet that allows the user
30 grains per square inch are measured at a mag- to convert the concentration of one element of a
nification of 250 . two-element metal alloy from weight percent to
atom percent.
4.49 Determine the ASTM grain-size number if
25 grains per square inch are measured at a mag- 4.2SS Generate a spreadsheet that allows the user
nification of 75 . to convert the concentration of one element of
a two-element metal alloy from atom percent to
4.50 Following is a schematic micrograph that rep- weight percent.
resents the microstructure of some hypothetical
metal. 4.3SS Generate a spreadsheet that allows the user
to convert the concentration of one element of a
two-element metal alloy from weight percent to
number of atoms per cubic centimeter.
4.4SS Generate a spreadsheet that allows the user
to convert the concentration of one element of a
two-element metal alloy from number of atoms
per cubic centimeter to weight percent.

DESIGN PROBLEMS
Specification of Composition
4.D1 Aluminum–lithium (Al–Li) alloys have been
developed by the aircraft industry to reduce the
weight and improve the performance of its air-
craft. A commercial aircraft skin material having
a density of 2.47 g/cm 3 is desired. Compute the
concentration of Li (in wt%) that is required.
Determine the following: 4.D2 Copper (Cu) and platinum (Pt) both have the
(a) Mean intercept length FCC crystal structure, and Cu forms a substi-
tutional solid solution for concentrations up to
(b) ASTM grain-size number, G approximately 6 wt% Cu at room temperature.
4.51 The following is a schematic micrograph that Determine the concentration in weight percent
represents the microstructure of some hypotheti- of Cu that must be added to Pt to yield a unit cell
cal metal. edge length of 0.390 nm.