Question#2: List and EXPLAIN the basic process available to make a material stringer for
yield?
1. Strengthening by grain size reduction As grain size is reduced, the stress required for
deformation increases. Grain size reduction is typically achieved by
CHAPTER 5:
5.2 Self-diffusion involves the motion of atoms that are all of the same type; therefore it is not subject to
observation by compositional changes, as with interdiffusion. Suggest one way in which self-diffusion may
be monitored.
Solution
Self-
Now, in order to solve for n in Equation 4.16, it is first necessary to take logarithms as
log N (n 1) log 2
From which n equals
log N
1
log 2
log 10
1 4.3
log 2
n
4.34 For an ASTM grain size of 8, approximately how many grains would there be per square
5.11 Determine the carburizing time necessary to achieve a carbon concentration of 0.45 wt% at a
position 2 mm into an ironcarbon alloy that initially contains 0.20 wt% C. The surface concentration is
to be maintained at 1.30 wt% C, and the treatment is t
5.12 An FCC iron-carbon alloy initially containing 0.35 wt% C is exposed to an oxygen-rich and virtually
carbon-free atmosphere at 1400 K (1127C). Under these circumstances the carbon diffuses from the alloy
and reacts at the surface with the oxygen in th
Note: this problem may also be solved using the Diffusion module in the VMSE software. Open the
Diffusion module, click on the Diffusion Design submodule, and then do the following:
1. Enter the given data in left-hand window that appears. In the window b
5.22 The diffusion coefficients for silver in copper are given at two temperatures:
T (C)
D (m2/s)
650
5.5 1016
900
1.3 1013
(a) Determine the values of D0 and Qd.
(b) What is the magnitude of D at 875C?
Solution
(a) Using Equation 5.9a, we set up two sim
1. In the left-hand window that appears, enter the two temperatures from the table in the book (converted
from degrees Celsius to Kelvins) (viz. 923 (650C) and 1173 (900C), in the first two boxes under the
column labeled T (K). Next, enter the correspondi
5.D1 It is desired to enrich the partial pressure of hydrogen in a hydrogen-nitrogen gas mixture for which
the partial pressures of both gases are 0.1013 MPa (1 atm). It has been proposed to accomplish this by
passing both gases through a thin sheet of so
4.27 For an FCC single crystal, would you expect the surface energy for a (100) plane to be greater or
less than that for a (111) plane? Why? (Note: You may want to consult the solution to Problem 3.54 at the
end of Chapter 3.)
Solution
The surface energy
5.8 A sheet of BCC iron 1 mm thick was exposed to a carburizing gas atmosphere on one side and a
decarburizing atmosphere on the other side at 725C. After having reached steady state, the iron was
quickly cooled to room temperature. The carbon concentrati
5.18 At what temperature will the diffusion coefficient for the diffusion of copper in nickel have a value of
6.5 10-17 m2/s. Use the diffusion data in Table 5.2.
Solution
Solving for T from Equation 5.9a
T =
Qd
R (ln D ln D0 )
and using the data from Ta
and, after some algebraic manipulation
N
Qv = kT ln v
N
7.57 1023 m 3
= (8.62 10 5 eV/atom K) (500 C + 273K) ln
5.851028 m 3
= 0.75 eV/atom
4.5 For both FCC and BCC crystal structures, there are two different types of interstitial sites. In each
cas
The interstitial atom that just fits into this interstitial site is shown by the small circle. It is situated in the
plane of this (100) face, midway between the two vertical unit cell edges, and one quarter of the distance
between the bottom and top cell
4.23 Molybdenum forms a substitutional solid solution with tungsten. Compute the weight percent of
molybdenum that must be added to tungsten to yield an alloy that contains 1.0 1022 Mo atoms per cubic
centimeter. The densities of pure Mo and W are 10.22 a
4.18 Some hypothetical alloy is composed of 12.5 wt% of metal A and 87.5 wt% of metal B. If the densities
of metals A and B are 4.27 and 6.35 g/cm 3, respectively, whereas their respective atomic weights are 61.4
and 125.7 g/mol, determine whether the cry
ave =
100
C Ag
Ag
=
100
75 wt%
25 wt%
3
10.49 g /cm
12.02 g /cm3
= 10.83 g/cm
And for the average atomic weight
Aave =
3
100
C Ag
AAg
=
C Pd
Pd
C Pd
APd
100
75 wt %
25 wt%
107.9 g / mol
106.4 g / mol
= 107.5 g/mol
Now, VC is determined from Equa
4.9 Calculate the composition, in weight percent, of an alloy that contains 218.0 kg titanium, 14.6 kg of
aluminum, and 9.7 kg of vanadium.
Solution\
The concentration, in weight percent, of an element in an alloy may be computed using a modified
form of
4.17 Calculate the unit cell edge length for an 85 wt% Fe-15 wt% V alloy. All of the vanadium is in solid
solution, and, at room temperature the crystal structure for this alloy is BCC.
Solution
In order to solve this problem it is necessary to employ Equ
In order to determine the average grain diameter, it is necessary to count the number of grains intersected
by each of these line segments. These data are tabulated below.
Line Number
No. Grains Intersected
1
11
2
10
3
9
4
8.5
5
7
6
10
7
8
The average num
Is it possible to purify hydrogen gas in this manner? If so, specify a temperature at which the process may be
carried out, and also the thickness of metal sheet that would be required. If this procedure is not possible, then state
the reason(s) why.
Solu