Prince Mohammad Bin Fahd University
Department of Mechanical Engineering
MEEN3393: Mechanical Engineering Design III
Dr. Sathyan Krishnan
Saeed Alqarni
yahya almarqabi
Mohammad Al Marri
Jumah Alramadhan
xxxxxxxxx
201000036
200700560
201000003
Assignment 1
1
Metal alloys are usually separated into two classes—ferrous and nonferrous alloys.
Ferrous Alloys are any alloys which have iron as the main substance (1). According
figure 1 below, ferrous metals are divided into steels and cast irons. In this paper we
are going to look into the low alloy steels which are named Plain Carbon Steel.
But first, what is an alloy?
Alloys are metallic materials consisting of two or more elements combined together in
a ways that they cannot be separated physically. Alloys represent around 90% of the
elements used in the industry. The purpose of using alloys is to gain metallic elements
that have different characteristics from the alloys constituents (6).
Figure 1: Classifications of metal alloys
Plain carbon steels are the most widely used type of steels. They are made of iron
and low concentrations of carbon along with impurities of other elements. The
concentration of carbon in the plain carbon steels is mostly below 1 wt%, but can go
up to 1.5 wt% (2). According to the concentrations of carbon in the steel, plain carbon
steels can be divided into three categories—low carbon steels, medium carbon steels
and high carbon steels.
Low carbon steels have carbon concentrations below 0.25 wt%. These alloys are the
most carbon steel produced in great quantities. They are relatively soft and weak;
however, they have a very good ductility and toughness. Some of the applications for
the low carbon steels are in automobile body part, structural shapes such as I-beams,
channels and angle iron and they can be used in pipelines, buildings…etc.
2
Medium carbon steels have carbon content between 0.25 wt% and 0.6 wt%. As a
result they have better machinability when subjected to heat treatments. They are also
more adaptable to machining, forging and where surface harness is desirable. Medium
carbon steels are stronger but less ductile and tough that the lower carbon steels.
These alloys are used in railways for both wheels and tracks. They also are desirable
for gears, crankshafts and machine parts.
High carbon steels contain carbon in concentration starting from 0.6 wt% an up to
1.4 wt%. These alloys are the hardest and strongest between all three kinds of alloys;
but they are the least ductile. As mentioned, high carbon steels are very hard, thus,
especially with proper heat treatments they are able to withstand high shear stresses.
They will also be very wear resistance and capable of holding a sharp cutting edge. As
a result, high carbon steels are used for drills, saws blacksmith tools, pipe cutters and
so on.
The following graph illustrates how some of the mechanical prosperities change when
the carbon concentration changes.
As carbon concentration increases
Ductility
Hardness & Strengths
Figure 2: relationship between the concentration of carbon and the mechanical prosperities of the
plain carbon steel alloys
3
This table shows some of the mechanical prosperities for plain carbon steels
Material
0.2% C
Steel
0.4% C
Steel
0.8% C
Steel
Density
Thermal
Thermal
Young's
103 𝑘𝑔𝑚−3 Conductivity Expansion Modulus
ty 𝐽𝑚−1 𝐾 −1 10−6 𝐾 −1 𝐺𝑁𝑚−2
𝑠 −1
7.86
50
11.7
210
Tensile
Strength
𝑀𝑁𝑚−2
%
elongation
350
30
7.85
48
11.3
210
600
20
7.84
46
10.8
210
800
8
Table 1: mechanical properties of plain carbon steels at different carbon concentrations
Heat treatments can improve the mechanical prosperities of the carbon steel alloys.
Heat treatment is used to acquire better ductility and to develop toughness, strength,
hardness and to relieve internal stresses. They many applications used for heat
treatment. Here we are going to briefly mention four of those applications.
Annealing: This process requires heating the material above its critical temperature,
maintain the temperature for a certain period of time, and then slow cool the material
The annealing process is used to soften the material, relieve internal stresses caused
by manufacturing and to improve machinability curve 2 in figure 3 illustrates the
period of time used for cooling.
Normalizing: Uses the same process of heating for annealing. However, the cooling
of the metal is done by air; and it takes far less time than annealing. Look at curve 3 in
figure 3.
Normalizing also softens the metal and relieves internal stresses. In addition it refines
the grain size and the metallurgical structure; and can break dendrite in the metal to
improve machinability and mechanical properties.
Hardening: This process involves quenching the metal into a fluid such as oil or
water, after heating it up above its critical temperature. This process is done rapidly to
insure better hardness. The downside of hardness is that it makes the metal very
brittle.
Tempering: The tempering process is usually done after hardening in order to reduce
the excess hardness in the metal. This process involves heating the metal into a
temperature lower that the temperature used for hardening.
As a rule of thumb, the higher the tempering temperature, the lower the hardness, and
the higher the toughness of the metal.
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Figure 3: idealized curve for plain carbon steel
Not all types of steel are going to responds to all different kinds of heat treatment. The
following table simplifies how different carbon concentration steel alloys should be
heat treated
Anneal
Normalize
Harden
Temper
Low Carbon <0.3%
Yes
Yes
No
No
Medium Carbon 0.3-0.5%
Yes
Yes
Yes
Yes
High Carbon >0.5%
Yes
Yes
Yes
Yes
Table 2:
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In the first half of this paper, we have discussed one of the materials in the ferrous
metal alloys group. Now, we are going to learn about a couple of materials in the non
ferrous metal alloys group.
Non ferrous metal alloys are the other group list under metal alloys. It includes all
alloys that do not include iron as their main constituent.
Copper Alloys
The Name of the material:
Copper
Structure and Composition:
Figure 4
In the first, we look to the crystal structure of copper is called the "face centered
cubic", or for short, "FCC" structure. However, the chemical element with the symbol
of copper is Cu and atomic number 29.In addition, copper metal is a ductile metal
with very a high thermal and electrical conductivity. In addition, Pure copper is soft
and malleable; and its freshly exposed surface has a reddish-orange color. Its
chemical reaction with most minerals and acids are easier than other materials. (7)
Mechanical properties:
Copper has several properties in many fields such as physical, mechanical, and
chemical etc. one of the most famous properties about copper is that it is an excellent
electrical conductor. On the other hand, copper is a good thermal conductor which
6
gives it wide range of applications many depending on which of its prosperities is
desired (11).We look at these other properties:

a good electrical conductor

a good thermal conductor

corrosion resistant

antibacterial

easily joined

ductile

tough

non magnetic

attractive colour

easy to alloy

recyclable

catalytic
Heat treatment process:
Copper and copper alloys may be heat treated for several purposes, described in this
article. (7,9)
Homogenizing
Homogenizing is applied to dissolve and absorb segregation and coring found in
some cast and hot worked materials, chiefly those containing tin and nickel.
Annealing
Annealing of cold worked metal is accomplished by heating to a temperature that
causes re-crystallization and, if maximum softening is desired, by heating well above
the re-crystallization temperature to cause grain growth. Method of heating, furnace
design, furnace atmosphere, and shape of work piece are important, because they
affect uniformity of results, finish, and cost of annealing.
For copper and brass mill alloys, grain size is the standard means of evaluating a recrystallizing anneal. Because many interacting variables influence the annealing
process, it is difficult to predict a specific combination of time and temperature that
will always produce a given grain size in a given metal.
Stress Relieving
7
Stress relieving is aimed to reduce or eliminate residual stress, thereby reducing
the likelihood that the part will fail by cracking or corrosion fatigue in service. Parts
are stress-relieved at temperatures below the normal annealing range that do not cause
re-crystallization and consequent softening of the metal.
Precipitation Hardening
High strength in most copper alloys is achieved by cold working. Solution treating
and precipitation hardening is applied to strengthen special types of copper alloys
above the levels ordinarily obtained by cold working.
Common Applications:
The areas of application for copper are varied: due to its good electrical
conductivity, copper is ideal for applications in electrical engineering, electronics and
telecommunications. The increasing interconnectedness of our office world, the rising
demands on telecommunications at home, but also the high safety and comfort
standards in car designs today ensure that copper demand is constantly on the
increase. Nowadays, some 25 kg of copper are used on average in each car – in luxury
models it can be more than twice this amount. Our modern lifestyle would not be
possible without copper. (10)
But copper also has a place in architecture and construction. In addition to
electrical cables made of copper, we also find copper pipes in water and heating
systems in our homes. Copper is often used for roofing and facades due to its good
corrosion resistance and, last but not least, because of its attractive appearance.
Aluminum alloys
The name of the material:
Aluminum alloy one of the non-ferrous alloys.
8
Structure and composition:
Figure 5
The previous figure 5 is an illustrated diagram for Aluminum Crystalline. This
structure shows the structure of pure aluminum without any impurities. The atomic
number of Al is 13 and the atomic mass 26.982, Al lies in group number 13 in
periodic table.
Aluminum alloys are many and the classification of them depends in contained
elements as Si, Fe, Mn, Mg and others.
Next table shows the composition of famous aluminum alloys which often used in
factoring.
Inter.
marking
1050
1060
1070
1080
3003
Table 3
DIN
marking
Al 99.5
Al 99.7
Al 99.8
AlMnCu
Si
Fe
Cu
Mn
Mg
Cr
Zn
0.25
0.25
0.2
0.15
0.6
0.4
0.35
0.25
0.15
0.7
0.05
0.05
0.04
0.03
0.2
0.05
0.03
0.03
0.02
1.5
0.05
0.03
0.03
0.02
0.05
0.05
0.03
0.04
0.03
0.1
Mechanical properties:
Here I will show mechanical properties of some common aluminum alloys.
Alloy
356
355
A354
A356
A357
C355
D712
Table 4
Tensile Strength
(103 psi)
32-40
32-50
47-55
38-40
33-50
35-50
34-40
Elongation
(%)
3-7
1-8
2-5
3-10
3-9
1-8
4-8
0.2%Yield Strength
(103 psi)
22-30
28-39
36-45
28-36
27-40
28-39
25-32
9
Heat treatment process:
Heat treatment of aluminum alloys occurs by heating at specific temperatures to
change the mechanical properties of alloy and achieve to needed properties with new
gain structure and more or less hardness. The heat treatment process can be one or
combination of operations as heating and cooling at different temperatures.
There are three heat treatment processes to change the properties of aluminum alloys:
1- Annealing
2- Solution Heat Treatment
3- Precipitation Heat Treatment (Artificial Aging).
The heat treatment of Aluminum alloys depend on the nature of needed applications
as aircrafts or cars.
Common applications:
The applications of aluminum and aluminum alloys cover these fields:
1- Electrical Conductors.
2- Transport
3- Packaging
4- Building and Architecture
5- Miscellaneous Applications
6- High Pressure Gas Cylinders
7- Machined Components
8- Ladders and Access Equipment
9- Sporting Equipment
10- Road Barriers and Signs
11- Domestic and Office Furniture
12- Lithographic Plates
Now a day, the use of aluminum has become more than the use of steel, because of
the properties of Al are better than steel especially in corrosion resistance.
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