Material Engineering
Analysis of the Behavior of Specific Materials for Specific Applications
Abstract
The purpose of this report is to analyze the behavior of specific materials for a
specific application. By identifying characteristics of different materials, choice of the
optimum material for a particular application is determined, and where such a material
doesn’t exist, a combination of two or more materials is used in order to achieve the
desired property, as has been made possible by recent advancement in nanotechnology
and material science.
Contents
Contents …………………………………………………………………………..3
List of Figures…………………………………………………………………….5
List of Tables………………………………………………………………………6
Chapter 1: Introduction…………………………………………………………..7
Chapter 2: Corrosion of high strength Al-alloys………………………………..7
Chapter 3: Ni-based super-alloys applications & properties………………….13
Chapter 4:-Ceramics, as the
High Temperature Materials for Automotives…………………………………16
Chapter 5: Advanced Fiber Reinforced Composite Materials…………………..17
Chapter 6: Intermetallis Materials Application for High Temperature
(Ti X Al, Ni X Al )…………………………………………………………..20
Chapter 7: Biomaterials……………………………………………………………21
Chapter 8: Semiconductors and their Applications…………………………….22
Chapter 9: Materials for sport goods……………………………………………22
Chapter 10: Solar Cell Materials………………..……………………………….24
Bibliography………………………………………………………………………..27
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List of Figures
Fig. 1: Generalised illustration of pitting corrosion on aluminium alloys
Figure 2. Cross section of pitting attack on AA6082 aluminium alloy after exposure to
marine atmosphere for 6 months. The dark spots are intermetallic particles.
Figure 3. SEM image of IGC attack on a AA6005
aluminium alloy exposed in acidic NaCl solution. A
Figure 4. SEM image of IGC attack on a AA6005
Figure 5. Short transverse cross section showing
Figure 6. The relationship between the action (A)/ reaction (R) force, the normal (N)
force, and the friction (F) force
Analysis of the Behavior of Specific Materials for Specific Applications
Chapter 1: Introduction
This study examines the properties of specific materials for a specific application.
Pressing environmental concerns has made it necessary to look for more efficient use of
material and energy resources. Understanding the properties of materials and attempting
to combine them in order for them to complement each other in behavior is the ultimate
goal. This is because we rarely find a material with all the desired characteristics
occurring naturally.
In this paper, different materials have been considered and their uses analyzed in
relation to the characteristics which make them suitable for the application.
Chapter 2: Corrosion of high strength Al-alloys
Aluminium alloys are used where high strength to weight ratio is needed such as
in the transportation industry. Naturally, aluminium forms an oxide layer on its surface
which protects it from corrosion, but will however corrode if exposed to harsh conditions.
Aluminium can be fabricated in order to give it a longer life and make it more reliable.
Though Aluminium is an active metal from a thermodynamic point of view, it quickly
gets covered with an inactive oxide layer when exposed to an environment containing
oxygen. This oxide layer renders it inactive. The thickness of this oxide layer depends on
 Temperature,
 Environment, and
 Alloy elements.
The oxide layer may be destabilised by the following factors and lead to corrosion:
 The oxide is unstable in acidic or alkaline environments (4<pH>9).
 It may be attacked by Chlorides and Fluorides locally.
The oxide becomes destabilised when some elements such as Ga, Tl, In, Sn and Pb
become incorporated in it. (. Pourbaix, 1974).

Most commercial aluminium alloys contain a number of intermetallic phases. Aluminium
alloys corrosion is essentially due to microgalvanic process between these phases and the
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3
matrix alloy. Due to the Fe content, the surrounding aluminium undergoes localized
attack. Also of importance are the following phenomena which may also occur:
 Preferential corrosion of an active phase
 A corroding phase may be sacrificed and serve as an anode and offer protection to
the surrounding material.
 The composition and pH of the electrolyte may change from that of the bulk
electrolyte.
In the matrix alloy and intermetalic phases, active components may corrode selectively
(dealloying), resulting in altered corrosion properties. (Shimizu,1991).

Figure 1: Generalised illustration of pitting corrosion on aluminium alloys
Figure 2. Cross section of pitting attack on AA6082 aluminium alloy after exposure to
marine atmosphere for 6 months. The dark spots are intermetallic particles.
Figure 3. SEM image of IGC attack on a AA6005
aluminium alloy exposed in acidic NaCl solution. A
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noble particle remains in the grain boundary zone.aluminium alloy exposed in acidic
NaCl solution. A
noble particle remains in the grain boundary zone.
Figure 4. Short transverse cross section showing
IGC attacks on a AA6005 aluminium alloy exposed
in acidic NaCl solution.
Pitting
Pitting is the creation of pit-like formations on the alloy and occurs when highly localized
corrosion takes place in the presence of aggressive chloride ions. These pits are
Created at weak regions in the oxide by chloride attack [4,5]. Pits are formed according
to the reactions
Al = Al3+ + 3e-……………………………………….. (1)
Al3+ + 3H2O = Al(OH)3 + 3H+ ………………………(2)
evolution of H2 and reduction of O2 are the important reduction processes at the
cathodes, as sketched in
Figure 1 above
2H+ + 2e- = H2 (3)
O2 + 2H2O + 4e- = 4OH- (4)
Propagation of a pit changes the environment inside the pit (anode). According to
reaction 2 the pH will decrease. To balance the positive charge produced by reaction 1
and 2, chloride ions will migrate into the pit and Hydrochloric acid formation inside the
pit causes accelerated pit propagation. The reduction process causes local alkalinisation
around cathode-acting particles. As mentioned above, aluminium oxide is not stable in
such environment, and aluminium around the particles will dissolve (alkaline pits). The
active aluminium component of the particles will also dissolve selectively, thereby
enriching the particle surface with Fe and increasing its cathodic activity. Etching
of the aluminium matrix around the particles may detach the particles from the surface,
which may repassivate the alkaline pits. This may also reduce the driving force for the
acidic pits causing repassivation of some in the long run. ( Hatch, 1984, pages 242-264).
Superalloys have been developed to meet specialized and specific characteristics
and applications. They are mostly used where the material needs to withstand stress at
high temperatures. One of the main applications for nickel-based superalloys is in aircraft
propulsion and in gas-turbine-engine disc components for land-based power generation.
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These superalloys are highly optimized due to the harsh conditions under which they
operate.(Noel, Furrer and Lemsky, 2001)
By having a good knowledge and making good use of alloy chemistry, the
mechanical properties of nickel based superalloys can be optimized through refined
special practices and process control. They are complex alloys with multistructural
features that dictate their mechanical properties. These features include:
 Grain size,
 Gamma-size and distribution,
 Carbide and boride-phase content, and
 Grain boundary morphology.
The following are observations are from the present inventions seeking to provide a novel
nickel base superalloy.
 Addition of cobalt and titanium to Udimet 720Li increases the capability
of the alloy to withstand high temperature and stres. Cobalt modifies the
solubility of the gamma prime phase in the gamma phase, raises the
solidus temperature, lowers the gamma prime solvus temperature and
lowers the stacking fault energy.
 the volume fraction of gamma prime phase is increased by the addition of
titanium which forms Co 3 Ti with the same crystal structure as Ni 3 Al.
 addition of higher levels of cobalt and titanium to Udimet 720Li make the
superalloy more prone to macro segregation during the casting process,
suggesting a powder metallurgy process is more suitable for
manufacturing large articles and limiting segregation to the nano-scale.
One preferred nickel base superalloy consists of 46.34 wt % nickel, 24 wt % cobalt, 14.5
wt % chromium, 5 wt % molybdenum, 3 wt % aluminium, 4.5 wt % titanium, 2 wt %
tantalum, 0.55 wt % hafnium, 0.06 wt % zirconium, 0.03 wt % carbon, 0.02 wt % boron.
The present invention also provides a nickel base superalloy consisting of 24 to 27 wt %
cobalt, 10 to 15 wt % chromium, 3 to 6 wt % molybdenum, 0 to 5 wt % tungsten, 2.5 to 4
wt % aluminium, 3.4 to 5 wt % titanium, 1.35 to 2.5 wt % tantalum, 0.5 to 1 wt %
hafnium, 0 to 0.1 wt % zirconium, 0.01 to 0.05 wt % carbon, 0.01 to 0.05 wt % boron, 0
to 0.2 wt % silicon and the balance nickel plus incidental impurities.
The starting chemistry for a nickel base superalloy according to the present invention is
RR1000 nickel base superalloy. The RR1000 nickel base superalloy is a gamma/gamma
prime strengthened superalloy, which has a gamma prime composition of Ni 3
(Al/Ti/Ta/Hf) and an increased volume fraction of gamma prime over Udimet 720Li. The
addition of cobalt and titanium to the RR1000 nickel base superalloy increases the
gamma prime volume fraction further and changes the gamma prime chemistry to
(Ni/Co) 3 (Al/Ti/Ta). In addition there is precipitation of a Co 3 Ta phase and/or Co 3 Ti
phase. Alternatively cobalt and titanium may be added to other advanced nickel base
superalloys.
TABLE 1
Alloy Invention Broad Preferred
wt % RR1000 A
B
Range
Range
Material Engineering
Ni
Co
Cr
Mo
W
52.3
18.5
15
5
0
46.34
24
14.5
5
0
43.35
27
14.5
5
0
Balance
23 to 40
10 to 15
3 to 6
0 to 5
Balance
24 to 27
10 to 15
3 to 6
0 to 5
Al
3
3
3
2.5 to 4
2.5 to 4
Ti
3.6
4.5
4.5
3.4 to 5
3.4 to 5
Ta
Nb
2
0
2
0
2
0
1.35 to 2.5 1.35 to 2.5
0 to 2
0
Hf
0.5
0.55
0.55 0.5 to 1
0.5 to 1
Zr
0.06
0.06
0.06 0 to 0.1
0 to 0.1
C
B
0.027
0.015
0.03
0.02
0.027 0.01 to 0.05 0.01 to 0.05
0.015 0.01 to 0.05 0.01 to 0.05
Si
0
0
0
0 to 2
6
0 to 0.2
Table 1 shows the compositions of alloys according to the present invention and the prior
art alloy RR1000.
The advantages of the present invention is that the nickel base superalloy has an increase
in the volume fraction of the gamma prime phase, the precipitation of gamma prime
phase with a Co 3 (Ta/Nb) chemistry, powder metallurgy processing route eliminates
macro-segregation and allows more alloying additions. The nickel base superalloy has
lower density than conventional nickel base superalloys due to the increased level of
cobalt. The level of gamma prime forming elements is not too high. There is a reduced
tendency for formation of TCP phases by control of chromium, titanium and the
aluminium to titanium ratio. The level of cobalt is determined using the fact that it is
known to generate a minimum stacking fault energy promoting planar deformation when
there is at least 15 wt % cobalt. Cobalt is also considered to reduce fatigue crack growth
rates as less damage accumulation occurs in planar slip, due to the ease of slip reversal.
Addition of more than 20 wt % cobalt increases the volume fraction of gamma prime
precipitates and substitutes for nickel. Higher levels of cobalt reduce the gamma prime
solvus temperature.
The level of chromium is controlled to balance a requirement for reduced fatigue crack
propagation rates, e.g. higher levels of chromium, and greater propensity for TCP phase
formation, e.g. lower levels of chromium. Molybdenum and tungsten are both beneficial
for creep properties. The beneficial effects on tensile strength and ductility at high
temperatures through solid solution strengthening are balanced against the propensity to
form TCP phases. Tantalum is controlled at a level to reduce crack growth and stabilise
the MC carbide. Tantalum controls the volume fraction of gamma prime phase with
aluminium and titanium. Titanium is controlled with levels of tantalum to provide
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volume fraction of gamma prime phase. Additional titanium lowers the gamma prime
solvus temperature. The maximum amount of titanium is controlled to prevent excessive
formation of TCP phases. Aluminium is controlled with the levels of tantalum and
titanium to optimise strength.
Chapter 4:-Ceramics, as the High Temperature Materials for Automotives
Today, valves are expected to handle increasingly difficult applications. These
often involve high temperatures and pressures, combined with difficult-to-handle fluids.
Therefore, the choice of materials for valves must be re-examined, because the old
materials may not be good enough.
Today, high temperature ceramics are expected to solve most of the problems of
manufacturing high performing parts of automobiles. These are especially the parts that
have to withstand high temperatures and pressures. This is the reason why automobile
manufactures are reassessing the choice of materials that they use for making various
parts of vehicles because the old materials may not be the best. These include:
 Valves
Valves are customarily made from metallic materials. However, in recent times
ceramics are gaining popularity in this area. Owing to their high resistance to
corrosion, abrasion and the ability to withstand high temperatures, ceramics can
be the perfect choice for use in operations that involve high flow rates,
temperatures above 600°F or media that are rough and abrasive. Ceramics also
saves money in
terms of maintenance and durability. Ceramics can be used
in retrofitting and in making new valves. Ball valve seats and seat balls are
usually retrofitted.
 Bearings
Graphite-metal bearings are in use because they can handle harsh
conditions that squash liquid- lubricated types. Graphalloy bearings and bushings
are available as flanged
bushings, thrust washers, and pillow blocks and
have the advantage of having high compression strength.
 Ceramic Fuel Cells
High temperature ceramic fuel cells are used for power generation and are commonly
more commonly known as solid oxide fuel cells or SOFCs. They have the advantage of
being clean in operation and use low pollution technology. Unlike traditional energy
conversion systems, they are highly efficient, reliable and emit very low levels of NOx
and Sox. In addition they are quiet and vibration-free.
Chapter 5: Advanced Fiber Reinforced Composite Materials
Fiber reinforced polymer matrix composite materials are used mostly in
aeronautics and marine engineering and are presently being considered for use in the
renewal of civil infrastructure ranging from bridge columns construction to reinforcement
of parking garage floor slabs. In future their use may also extend to replacement of bridge
decks and in construction of new bridge structures. They are corrosion resistance,
durable, and have low density. This makes them applicable in areas where use of other
materials might be constrained due to durability, weight or lack of flexibility.
Composite materials are microscopic or macroscopic combination of two or more
materials with a distinct interface between them. The definition can be restricted to
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include those materials that consist of a reinforcing phase such as fibers or particles
supported by a matrix phase for structural applications. Composite materials have the
following features:
(1) The distribution of materials in the composite is controlled by mechanical
means;
(2) The term composite is usually reserved for materials in which distinct phases
are separated on a scale larger than atomic, and in which the composite's
mechanical properties are significantly altered from those of the constituent
components;
(3) These materials can be looked at as a combination of two or more materials
that are used in combination. The aim is to rectify a weakness in one material by
strength in another.
(4) according to a recently developed concept, a composite is not only a
combination of two materials, but the combination should have its own distinctive
features in terms of strength, heat resistance etc, and must be better than either of
the component materials alone.
Composites were developed because no single, homogeneous structural material could be
found that had all of the desired characteristics for a given application. Fiber-reinforced
composites were first developed to replace alloys, which provide high strength and are
fairly stiff at low density although they are subject to corrosion and fatigue.
A glass-reinforced plastic fishing rod is an example of a composite material in which
glass fibers are placed in an epoxy matrix. Glass fibers are characterized by their high
tensile stiffnesses and very high tensile strengths. However, their small diameters don’t
allow for much bending stiffness. The rod would have good bending stiffness, but poor
tensile properties if it were made epoxy plastic alone. The presence of the fibers gives the
structure high tensile stiffness, high tensile strength, and high bending stiffness. Fibers
are the source of almost all of the load-carrying characteristics (strength and stiffness) of
the composite in a high-performance fiber-reinforced composite. The fibers in such a
composite are in form bundles such that even if several fibers break, the load is
redistributed to other fibers, which avoids disaster. Glass fibers are also used for
nonstructural uses such as panels in aircraft and rocket-motor cases and pressure vessels.
Attack by moisture poses problems for the use of glass fibers in other applications.
Matrices for high performance composites
The cohesive and adhesive characteristics of the matrix binds the fibers together
in the composite material. The matrix therefore transfers load to and between fibers, and
protects the fibers from hostile conditions. The matrix is therefore the weak link in the
composite, so when the composite is strained, the matrix may crack or debond from the
fiber surface, or break down under far lower strains than are usually desired. The most
widely used continuous-fiber composites are polyester and vinyl ester resins. They are
used for chemically resistant piping and reactors, truck cabs and bodies, appliances,
bathtubs and showers, car hoods, decks, and doors. These matrices are usually reinforced
with glass fibers, as it has been difficult to adhere the matrix to carbon and other fibers.
Resins, though more expensive, find applications as replacements for polyester and vinyl
ester resins in high performance sporting goods, piping for chemical processing plants,
and printed circuit boards.
Chapter 6: Intermetallics Materials Application for High Temperature
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(Ti X Al, Ni X Al )
A series of binary Al---Ti alloys and a range of Al---Ti based ternary alloys
containing additions of Ce and Ni have been produced by chill-block melt spinning with
a view to generating microstructures comprising a large volume fraction of finely and
homogeneously dispersed, thermally stable, intermetallic particles. The microstructures
and thermal stability of these alloys have been examined using transmission electron
microscopy and the ageing response of an Al---Ti---Ni alloy monitored using
microindentation hardness measurements. It has been established that high temperature
(300–400 °C) precipitation strengthening can be achieved in alloys based on the Al---Ti--Ni system, through rapid solidification and postsolidification heat treatment, and that
rapidly quenched Al---Ti---Ni alloys, with a weight ration Ti:Ni in the range (3:1)–(4:1),
appear to have significant potential for applications involving elevated temperatures.
Chapter 7: Biomaterials
A biomaterial is any material may be natural or man-made. It consists of either
whole or part of a living structure or biomedical device which performs, augments, or
replaces a natural function. Examples of these include dentures, prostheses etc.
Wettability is one important characteristic of a surface. Wettability of textile
fibers can be enhanced to assist the dyeing operation during processing; and the fibers
can be made to be non-wettable for application in, for example, ski clothing. PhotoLink
uses wettability technology, as illustrated below, to, for instance, improve the flow
characteristics of a polymer membrane used in a medical, diagnostic test kit.
Endo-vascular stents provide structural support vessels following angioplasty and
other major medical procedures. After an angioplasty procedure, vessels can experience
re-stenosis and eventually return to their original pre-operative diameter. In as many as
10% of the procedures, the vessels may even collapse immediately. To prevent the
vessels from shrinking, endo-vascular prosthesis or stents are used. Stents are tubular
structures consisting of a spring, wire mesh or slotted tubes that are deployed inside the
vessel.
Chapter 8: Semiconductors and their Applications
Construction of highly efficient and low noise pixel detectors of ionizing radiation
is now possible, thanks to recent advances in semiconductor technology. This has steadily
improved quality of front end electronics and enabled fast digital signal processing in
each pixel which offers recording of more complete information. about each detected. All
these features improve an extend applicability of pixel technology in different fields.
Some applications of this technology especially for imaging in life sciences will be
shown (energy and phase sensitive X-ray radiography and tomography, radiography with
heavy charged particles, neutron radiography, etc). On the other hand a number of
obstacles can limit the detector performance if not handled. The pixel detector is in fact
an array of individual detectors (pixels), each of them has its own efficiency, energy
calibration and also noise. The common effort is to make all these parameters uniform for
all pixels. However an ideal uniformity can be never reached. Moreover, it is often seen
Material Engineering 10
that the signal in one pixel can affect the neighboring pixels due to various reasons (e.g.
charge sharing). All such effects have to be taken into account during data processing to
avoid false data interpretation.
Chapter 9: Materials for sport goods
Advanced materials with mechanical and physical characteristics are now
replacing conventional high-volume materials such as steels and aluminum alloys. These
include glass reinforced composites and continuous fiber composites, which have
contributed significantly to the heightened performance of transportation systems in
aerospace, automobiles, and trains. These characteristics include strength, ductility,
stiffness (modulus), temperature capability, and low weight. For many high-performance
applications, high cost can be accepted, although the level of acceptance is dependent on
the industry in question.
As in the case of transportation industry, the materials of choice for sports have changed
a lot over time. From natural materials such as wood, gut, and rubber, we have
progressed to high-technology metals, polymers and ceramics, and synthetic-hybrid
materials including composites.
The optimum design of sports equipment, together
with other disciplines clearly requires an
understanding of materials science. In designing
sports equipment, the various characteristics of
materials must be considered. Among these
characteristics are strength, ductility, density,
fatigue resistance, toughness and cost.
Chapter 10: Solar Cell Materials
Solar cells can be made from a wide range
of semiconductor materials. These include:
 Silicon (Si)—including single-crystalline
Si, multicrystalline Si, and amorphous Si
 Polycrystalline thin films—including
copper indium diselenide (CIS), cadmium
Figure 6. The relationship between
telluride (CdTe), and thin-film silicon
the action (A)/ reaction (R) force,
 Single-crystalline thin films—including
the normal (N) force, and the
high-efficiency material such as gallium
friction (F) force (Courtesy of K.E.
arsenide (GaAs).
Easterling).
The important aspects of these materials that
need consideration are absorption, bandgap,
and complexity of manufacturing.
Absorbtion
The absorption coefficient of a material indicates how far light having a specific
wavelength (or energy) can penetrate the material before being absorbed. A small
absorption coefficient means that light is not readily absorbed by the material. Again, the
absorption coefficient of a solar cell depends on two factors: the material making up the
Material Engineering 11
cell, and the wavelength or energy of the light being absorbed. Solar cell material has an
abrupt edge in its absorption coefficient. The reason is that light whose energy is below
the material's bandgap cannot free an electron. And so, it isn't absorbed.
Bandgap
The bandgap of a semiconductor material is an amount of energy. Specifically, it's
the minimum energy needed to move an electron from its bound state within an atom to a
free state. This free state is where the electron can be involved in conduction. The lower
energy level of a semiconductor is called the "valence band." And the higher energy level
where an electron is free to roam is called the "conduction band." The bandgap (often
symbolized by Eg) is the energy difference between the conduction band and valence
band.
Crystallinity
The crystallinity of a material indicates how perfectly ordered the atoms are in the
crystal structure. Silicon, as well as other solar cell semiconductor materials, can come in
various forms: single-crystalline, multicrystalline, polycrystalline, or amorphous. In a
single-crystal material, the atoms making up the framework of the crystal are repeated in
a very regular, orderly manner from layer to layer. In contrast, in a material composed of
numerous smaller crystals, the orderly arrangement is disrupted moving from one crystal
to another. One classification scheme for silicon uses approximate crystal size and also
includes the methods typically used to grow or deposit such material.
Complexity of Manufacturing
The most important parts of a solar cell are the semiconductor layers, because this
is where electrons are freed and the electric current is created—it's the active layer
"where the action is," so to speak. Several different semiconductor materials are used to
make the layers in different types of solar cells, and each material has its benefits and
drawbacks.
The cost and complexity of manufacturing may vary across these materials and
device structures based on many factors, including deposition in a vacuum environment,
amount and type of material utilized, number of steps involved, need to move cells into
different deposition chambers or processing processes, and others.
A typical solar cell consists of a glass or plastic cover, an antireflective layer, a
front contact to allow electrons to enter a circuit, a back contact to allow them to
complete the circuit, and the semiconductor layers where the electrons begin and
complete their journey.(US Department of Energy, 2005).
Material Engineering 12
Bibliography
Pourbaix, M., (1974).Atlas of electrochemical equilibria in aqueous solutions, Huston:
NACE Cebelcor, ,
Noel, R, Furrer, D and Lemsky, J, (2001). Proceedings of the 3rd
ASM-International Paris Conference. Ohio: ASM.
Hatch, J. E., (1984). Aluminium - Properties and physical metallurgy,. Ohio: ASM.
US Department of Energy, (2005)