Download - 1. Intro to Materials Science
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INTRODUCTION TO
MATERIALS SCIENCE
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Introduction2
Materials make modern life possiblefrom the polymers in the chair youre sitting on, the metal ball-point pen youre using, and the concrete that made the building you live or work in to the materials that make up streets and highways and the car you drive.
All these items are products of materials science and technology
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Materials science and engineering3
Materials Science investigating relationships that
exist between the structure and properties of
materials.
Materials Engineering on the basis of these
structure-property correlations, designing or
engineering the structure of a material to produce a
pre-determined set of properties
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4 The combination of physics, chemistry, and the focus
on the relationship between the properties of a
material and its microstructure is the domain of
Materials Science.
The development of this science allowed designing
materials and provided a knowledge base for the
engineering applications (Materials Engineering).
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5Evolution of materials
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The world of materials7
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8 2003 Brooks/Cole Publishing / Thomson Learning
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Approach in Materials Science9
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Materials, process and shape10
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2003 Brooks/Cole Publishing / Thomson Learning
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2003 Brooks/Cole Publishing / Thomson Learning
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2003 Brooks/Cole Publishing / Thomson Learning
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2003 Brooks/Cole Publishing / Thomson Learning
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Structure15
At the atomic level: arrangement of atoms in
different ways (different properties for graphite
than diamond both forms of carbon.)
At the microscopic level: arrangement of small
grains of material that can be identified by
microscopy (different optical properties to
transparent vs. frosted glass.)
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graphite diamond
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Materials, processes and choice
Engineers make things out of materials; to make
something out of a material you also need a
process;
Not just any processthe one you choose has to be
compatible with the material you plan to use.
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E.g. the materials have to support loads, to insulate
or conduct heat and electricity, to accept or reject
magnetic flux, to transmit or reflect light, to survive
in often-hostile surroundings, and to do all these
without damage to the environment or costing too
much.
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Why do we study MSE24
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Material properties
Mechanical properties
Thermal properties
Electrical, magnetic and optical properties
Chemical properties
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Properties are the way the material responds to the
environment; for instance, the mechanical, electrical and
magnetic properties are the responses to mechanical,
electrical and magnetic forces, respectively.
Other important properties are thermal (transmission of
heat, heat capacity), optical (absorption, transmission
and scattering of light), and the chemical stability in
contact with the environment (like corrosion resistance).
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Mechanical properties29
The properties of a material are those that reveal
its elastic and inelastic (plastic) behavior when force
is applied.
Thereby, those properties will indicate its suitability
for mechanical (load-bearing) application, fatigue
limit, hardness, modulus of elasticity, tensile strength,
and yield strength.
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Thermal properties
Thermal properties are
dependent on temperature;
therefore they are related to,
or caused by heat.
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This means that there is a limiting temperature
called the maximum service temperature, Tmax,
above which its use is impractical.
Stainless steel has a high Tmaxit can be used up to
800C; most polymers have a low Tmax and are
seldom used above 150C.
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Electrical, magnetic and optical properties
Electricity and magnetism are closely linked.
Electric currents induce magnetic fields; a moving
magnet induces, in any nearby conductor, an electric
current.
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The response of most materials to magnetic fields is too small to be of practical value.
Materials respond to light as well as to electricity and magnetismhardly surprising, since light itself is an electromagnetic wave.
Materials that are opaque reflect light; those that are transparent refract it, and some have the ability to absorb some wavelengths (colors) while allowing others to pass freely
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Chemical properties
A chemical property is any of a material's properties that becomes evident during a chemical reaction; that is, any quality that can be established only by changing a substance's chemical identity.
Chemical properties cannot be determined just by viewing or touching the substance; the substance's internal structure must be affected for its chemical properties to be investigated.
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Design-limiting properties
The performance of a component is limited by certain of the properties of the materials of which it is made.
This means that, to achieve a desired level of performance, the values of the design-limiting properties must meet certain targetsthose that fail to do so are not suitable.
Materials are chosen by identifying the design-limiting properties and applying limits to them, screening out those that do not meet the limits.
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Material family39
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The process tree41
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Process with shaping tree44
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Process with joining and surface treatment tree45
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Management for materials and processes46
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Steel manufacturing process48
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Typical mechanical properties51
The first two digits indicate carbon steel and the last two digits indicate the nominal carbon content in hundred of a percent
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Example process: video52
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Powder Processing
Powder processing relies on the semi-fluid character
of a powder to flow and fill a die at room
temperature, taking on the die shape.
Unlike machining where there is wasted material
and expense associated with mass removal, powder
approaches simply form the needed mass of
powder into the desired shape in a single step.
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Different from casting, which is only applied to
lower melting temperature metals, powder
techniques are applicable to all materials, including
diamonds, ceramics, and various compounds such as
tungsten carbide.
Indeed, many of the products formed using powders
are not available as castings.
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Powder injection molding55
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A stainless steel pump
housing showing the
shape complexity
possible with powder
injection molding
and the size change
between molding (left
component) and sintering
(right component).
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Powder-binder extrusion
Powder-binder extrusion
is used to form a
product that is long and
thin with a constant cross
section, such as a rod,
tube, honeycomb, or
twist drill.
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Other powder method59
A slurry cast bronze statue formed using a wax-polymer binder, bronze powder, and rubber tooling. After the slurry was cast and cooled, the shape was placed in a furnace and slowly heated to burn out the binder and sinter the particles. This technology is ideal for smaller production quantities, such as encountered in the art field.
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Ceramics Processing60
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Ceramics injection molding61
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Uniaxial pressing
Uniaxial (die) pressing involves the compaction of powder into a rigid die by applying pressure along a single axial direction through a rigid punch,plunger, or piston.
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Isostatic compaction63
Isostatic pressing, which is also known as isopressing, hydrostatic pressing, and cold isostatic pressing (CIP), provides a means of manufacturing complex shapes such as tubes and spark plug bodies, and larger volume parts that are not easily dry pressed.
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Extrusion
Extrusion of (a) a rod and (b) a tube.
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Injection molding65
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Slip Casting66
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Tape casting67
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Polymer processing
One of the most outstanding features of plastics is
the ease with which they can be processed.
In some cases semi-finished articles such as sheets or
rods are produced and subsequently fabricated
into shape using conventional methods such as
welding or machining.
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In the majority of cases, however, the finished article,
which may be quite complex in shape, is produced in a
single operation.
The processing stages of heating, shaping and cooling
may be continuous (e.g. production of pipe by
extrusion) or a repeated cycle of events (e.g.
production of a telephone housing by injection molding)
but in most cases the processes may be automated and
so are particularly suitable for mass production.
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There is a wide range of processing methods which may be used for plastics.
In most cases the choice of method is based on the shape of the component and whether it is thermoplastic or thermosetting.
It is important therefore that throughout the design process, the designer must have a basic understanding of the range of processing methods for plastics since an ill-conceived shape or design detail may limit the choice of molding methods.
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Screw extruder71
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Extrusion stretch blow molding
Neck ring stretch blow molding
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Injection blow molding process73
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Extrusion coating process74
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References 75
B.S. Mitchell: An Introduction to Materials
Engineering and Science: for Chemical and
Materials Engineers, John Wiley & Sons, Inc.,
Hoboken, NJ, 2004
W.D. Callister, Jr.. Fundamentals of Materials
Science and Engineering, John Wiley & Sons, Inc.,
New York, 2001