Unlock document.
This document is partially blurred.
Unlock all pages and 1 million more documents.
Get Access
Chapter 3
Structure and Manufacturing
Properties of Metals
Questions
3.1 What is the difference between a unit cell and
a single crystal?
3.2 Explain why we should study the crystal struc-
formation about various properties can be in-
ferred. By relating structure to properties, one
3.3 What effects does recrystallization have on the
properties of metals?
As shown in Figs. 3.17 on p. 96 and 3.18 on
p. 97, strength and hardness are reduced, duc-
higher the ductility of the metal. Also, the slip
system and the number of active slip systems
for plastic deformation. See also Section 3.3.1
3.5 Explain what is meant by structure-sensitive
and structure-insensitive properties of metals.
structure-insensitive properties.
3.6 What is the relationship between nucleation
rate and the number of grains per unit volume
of a metal?
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
3.7 Explain the difference between recovery and re-
crystallization.
3.8 (a) Is it possible for two pieces of the same
metal to have different recrystallization temper-
atures? Explain. (b) Is it possible for recrys-
tallization to take place in some regions of a
workpiece before other regions do in the same
workpiece? Explain.
3.9 Describe why different crystal structures ex-
hibit different strengths and ductilities.
tility of a metal depends on how many of the
is the plane spacing), and the b/a ratio depends
on the slip system of the chemical structure.
(See also Section 3.3.1 starting on p. 87.)
become oriented nonrandomly in a workpiece
when it is deformed, because the slip direction
of a crystal tends to align along the general
deformation direction. Mechanical fibering is
caused by the alignment of impurities, inclu-
preferred orientation resulting from the recrys-
tallization process. Copper is an example of a
chanical fibering in a workpiece? Explain.
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
3.14 Explain why we may have to be concerned with
the orange-peel effect on metal surfaces.
Orange peel not only influences surface appear-
ance of parts, which may or may not be desir-
able, but also affects their surface characteris-
3.15 How can you tell the difference between two
parts made of the same metal, one shaped by
cold working and the other by hot working? Ex-
parts.
Some of the methods of distinguishing hot vs.
cold worked parts are:
(a) The surface finish of the cold-worked part
would be smoother than the hot-worked
(b) If hardness values could be taken on the
behavior.
(d) Metallographic examination of the parts
grain size increases.
Strength increases as more entanglements of
the strength will be lower. (See also Eq. (3.8)
on p. 92.)
3.17 What is the significance of some metals, such as
lead and tin, having recrystallization tempera-
tures at about room temperature?
formability. However, as the strain rate in-
creases, their strength at room temperature in-
creases because the metal has less time to re-
3.18 You are given a deck of playing cards held
together with a rubber band. Which of the
material-behavior phenomena described in this
chapter could you demonstrate with this setup?
What would be the effects of increasing the
number of rubber bands holding the cards to-
gether? Explain. (Hint: Inspect Figs. 3.5 and
The following demonstrations can be made with
Fig. 3.5a on p. 86.
(b) Surface roughness that develops along the
p. 99.
(e) Presence of a rubber band indicates elastic
behavior and recovery when unloaded.
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
3.19 Using the information given in Chapters 2 and
3, list and describe the conditions that induce
brittle fracture in an otherwise ductile piece of
metal.
tension components,
(d) radiation damage, and
for a (1) paper clip, (2) bicycle frame, (3) ra-
tions, the particular requirements that are sig-
(a) Yield stress, elastic modulus, corrosion re-
sistance.
3.21 Explain the advantages and limitations of cold,
These are explained briefly in Section 3.7 on
p. 98. Basically, cold working has the advan-
tages of refining the materials grain structure
while increasing mechanical properties such as
3.22 Explain why parts may crack when suddenly
subjected to extremes of temperature.
Thermal stresses result from temperature gra-
(See also Section 3.9.5 starting on p. 107 re-
3.23 From your own experience and observations,
(3) copper, (4) magnesium, and (5) gold.
There are numerous acceptable answers, includ-
ing:
3.24 List three applications that are not suitable for
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
(1) steel, (2) aluminum, (3) copper, (4) magne-
sium, and (5) gold.
car tire, portable computer case.
(b) aluminum: cutting tools, shafts, gears, fly-
3.25 Name products that would not have been devel-
oped to their advanced stages, as we find them
3.26 Inspect several metal products and components
and make an educated guess as to what mate-
3.27 List three engineering applications each for
(c) High thermal conductivity: cookware, car
radiators, precision instruments that resist
3.28 Two physical properties that have a major in-
fluence on the cracking of workpieces, tools, or
dies during thermal cycling are thermal conduc-
the stresses will be lower for a given tempera-
ture gradient. When thermal stresses reach a
traditional materials.
chasing an aluminum automobile?
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
3.31 Lead shot is popular among sportsmen for hunt-
ing, but birds commonly ingest the pellets
(along with gravel) to help digest food. What
substitute materials would you recommend for
lead, and why?
Obviously, the humanitarian concern is asso-
ciated with the waterfowl ingesting lead and,
therefore, perishing from lead poisoning; the
3.2 on p. 98, materials with a very high density
3.32 What are metallic glasses? Why is the word
“glass” used for these materials?
tation. Thus, none of the traditional metallic
characteristics are present, such as deformation
by slip, anisotropy, or grain effects. Because
this is very similar to the microstructure and
behavior of glass, hence the term.
3.33 Which of the materials described in this chap-
ter has the highest (a) density, (b) electri-
cal conductivity, (c) thermal conductivity, (d)
1050 MPa, and the highest cost (which varies
3.34 What is twinning? How does it differ from slip?
This is illustrated in Fig. 3.5 on p. 86. In twin-
3.35 Calculate the theoretical (a) shear strength and
(b) tensile strength for aluminum, plain-carbon
steel, and tungsten. Estimate the ratios of their
τ=G
2π
σ=E
10
2.1 on p. 32, and Gis calculated using Eq. (2.24)
on p. 49,
G=E
2(1 −ν)
Thus, the following table can be generated:
Mat- E G τ σ
3.36 A technician determines that the grain size of
a certain etched specimen is 6. Upon further
checking, it is found that the magnification used
was 150, instead of 100 as required by ASTM
standards. What is the correct grain size?
late from Table 3.1 on p. 93 or obtain the data
for a larger number of grain sizes, as well as the
grain diameter as a function of the ASTM No.
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
-3 1 0.7 1.00
-1 4 5.6 0.50
0 8 16 0.35
1 16 45 0.25
1.5= 0.0293mm
As can be seen from the table, this corresponds
As can be seen in Table 3.1 on p. 93, an ASTM
grain size of 9 has 185,000 grains/mm3. An or-
(50.5)(185,000)=9.34 million.
3.38 The natural frequency fof a cantilever beam is
given by the expression
where Eis the modulus of elasticity, Iis the
that any cross section will result in the same
trends, so students shouldn’t be discouraged
from considering, for example, circular cross
will decrease with increasing temperature (see
Fig. 2.9 on p. 41). Consider the ratio of initial
f2
0.56qE2I2g
w2L4
2
(W/L2)L4
2
L3
2
L2=L1(1 + α∆T)
Therefore, the frequency ratio is
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
3.3 on p. 106, the coefficient of thermal expan-
sion for steel is 14.5 µm/m◦C (average of the
extreme values given in the table), so that the
3.39 A strip of metal is reduced in thickness by cold
working from 25 mm to 15 mm. A similar strip
is reduced from 25 mm to 10 mm. Which one
of these strips will recrystallize at a lower tem-
perature? Why?
A review of Fig. 3.18 will indicate that, because
3.40 A 1-m long, simply-supported beam with a
round cross section is subjected to a load of 50
kg at its center. (a) If the shaft is made from
AISI 303 steel and has a diameter of 20 mm,
what is the deflection under the load? (b) For
shafts made from 2024-T4 aluminum, architec-
tural bronze, and 99.5% titanium, respectively,
what must the diameter of the shaft be for the
shaft to have the same deflection as in part (a)?
δ=P L3
48EI
δ=P L3
48EI =64P L3
48πEd4
Solving for d, we have
2024-T4 Al 79 25.2
Arch. bronze 110 23.2
If the grain size is 5, there are 2900 grains per
mm3of aluminum, and each grain has a volume
of 1/2900 = 3.45 ×10−4mm3. Recall that for
an fcc material there are four atoms per unit
cell, with a total volume of 16πR3/3, and that
the diagonal, a, of the unit cell is given by
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
0.25 nm or 0.25 ×10−6mm. The volume of an
aluminum atom is
or 6.54 ×10−20 mm3. Dividing the volume of
aluminum in the grain by the volume of an alu-
See Table 16.4.
16.4 on p. 971. Average values have been used
to obtain these plots.
600
800
1000
1200
Copper
Stainless steel Nickel
Tungsten
Titanium
Molybdenum
Steel
150
200
250
350
400
Elastic modulus (GPa)
Molybdenum
Nickel
Steel
3.43 The following data is obtained in tension tests
(µm) (MPa)
15 150
20 140
50 105
75 90
100 75
Does this material follow the Hall-Petch effect?
If so, what is the value of k?
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
160
100
120
140
0.05 0.3
The least-squares curve fit for a straight line is
Y= 35.22 + 458d−1/2
Material k α k/α
Plastics 0.4 72 0.00556
Wood 0.4 2. 0.20
Glasses 1.7 4.6 0.37
Lead 35. 29.4 1.19
Graphite 10. 7.86 1.27
Ceramics 17. 5.5 3.09
Iron 74. 11.5 6.43
Nickel 92 13.3 6.91
Gold 317. 19.3 16.4
Si 148. 7.63 19.3
Silver 429 19.3 22.2
Copper 393 16.5 23.8
Molybdenum 142 5.1 27.8
Tungsten 166. 4.5 36.9
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
