İleri Kompozit Malzemeler

Transcription

MME101 Introduction to
Metallurgy and Materials
Engineering
Asst. Prof. Dr. Ayşe KALEMTAŞ
Bursa Technical University, Metallurgical and Materials Engineering Department
Office Hours: Tuesday, 16:00-17:00
[email protected], [email protected]
Classifications of Materials
Materials
Metals
Polymers
A composite material is made by
combining two or more materials – often
ones that have very different properties.
The two materials work together to give
the composite unique properties. However,
within the composite you can easily tell
the different materials apart as they do
not dissolve or blend into each other.
A composite material can be defined as a
combination
of
a
matrix
and
a
reinforcement, which when combined
gives properties superior to the properties
of the individual components.
Ceramics
Composites
“If two heads
are better than
one, could two
materials be
better than
one?”
Composite Materials
Composite: Contains at least two phases, a multiphase material.
Combination of 2 or more materials
Each of the materials must exist more than 5%
Presence of interphase
The properties shown by the composite materials
are differed from the initial materials
• Can be produced by various processing techniques
•
•
•
•
Composite materials - a new emerging class of materials to
overcome a current limits of monolithic of conventional
materials
Materials
Metals
 Ferrous Metals
 Steels,
stainless steels,
tool and die
steels, cast irons
 Nonferrous Metals
 Aluminium,
copper,
titanium, zinc,
etc.
Polymers
 Thermoplastics
 PVC, nylon,
etc.
 Thermosets
 Epoxies,
phenolics, etc.
 Elastomers
 Rubbers,
silicones, etc.
Ceramics
Composites
 Advanced Ceramics
 Functional
ceramics
 Structural
Ceramics
 Traditional
Ceramics
 Whitewares,
cement, tiles,
bricks, etc.
 Metal matrix
composites
 Ceramic matrix
composites
 Polymer matrix
composites
 Amorphous Metals
General Categories of Engineering Materials Used Today in
Manufacturing Industries
• Hard, low density, corrosion and wear resistant, unreactive, very
high elastic modulus
Ceramics
• Brittle, low weibull modulus
• Soft, conductive, high fracture toughnes, ductile, reactive
Metals
• High density, low temperature use
• Easy to shape, very low density
Polymers
• Low modulus, low temperature use, very reactive, low melting
point
Introduction to Materials
A comparison of the properties of ceramics, metals, and polymers
Material Properties
Fracture Behavior
Very
Ductile
Modulate
Ductile
Large
Moderate
Brittle
Ductile fracture is
desirable !
Ductile: Warning before
fracture
Brittle : No warning
% RA or %EL :
Small
Materials Tetrahedron
Structure
Materials science and engineering tetrahedron : A tetrahedron diagram
showing how the performance-to-cost ratio of materials depends upon
the composition, structure, synthesis, and processing.
Structure
 arrangement of internal components
 subatomic
 atomic
 microscopic
 macroscopic (bulk)
Different ways for
shaping
materials
into
useful
components
or
changing
their
properties.
Processing
 method of preparing
material
Performance
Properties
 material characteristic
 response
to
external
stimulus
 mechanical,
electrical,
thermal,
magnetic,
optical, deteriorative
 behavior in a particular
application
Structure of Materials
STRUCTURE (length scale)
Subatomic
Atomic
Microscopic
Macroscopic
< 0.2 nm
0.2-10 nm
1-1000 µm
> 1 mm
The structure of a material usually relates to the arrangement
of its internal components
Subatomic
Structure
Atomic
Structure
Microscopic
Structure
Macroscopic
Structure
Electrons
within
individual atom
and interaction
with nuclei
Organization of
atoms or
molecules
related to one
another
Large groups of
atoms, direct
observation by
microscope
Structural
elements may
be viewed with
naked eye
Atomic Structure : Arrangement of atoms in materials (for the
same atoms can have different properties, e.g. two forms of
carbon: graphite and diamond)
An allotrope is a variant of a substance consisting of only one type of atom. It
is a new molecular configuration, with new physical properties.
Elemental carbon exists in nature mainly as two allotropes,
diamond and graphite.
Substances that have allotropes include carbon, oxygen, sulfur, and
phosphorous.
Allotropes of a given substance will often have substantial differences between
each other. For example, one allotrope of carbon, fullerene, is many times
stronger and lighter than steel. An allotrope should not be confused
with phase, which is a change in the way molecules relate to each other, not
in the way that individual atoms bond together.
An allotrope is a variant of a substance
consisting of only one type of atom. It is
a new molecular configuration, with new
physical properties.
Graphite
layer structure
Diamond
* weak van der Waal’s forces
between layers
* planes slide easily, good
lubricant
Polymorphs are compounds that have the same chemical composition
but different crystal structures.
Many ceramic materials show this behavior, including SiO2, BN,
BaTiO3, ZrO2 and BeO.
Transitions between the different polymorphs may occur as a result of
changes in temperature or pressure.
Polymorph
Tridymite
Cristobalite
Quartz (Beta)
Quartz (Alpha)
two polymorphs of silica (SiO2)
Density (g/cm3)
2.28
2.33
2.53
2.65
Crystal Structure
Hexagonal
Cubic
Hexagonal
Rhombohedral
hexagonal boron nitride (BN)
cubic boron nitride (BN)
A solid is a material that retains both its shape and volume over time. If a solid
possesses long range, regularly repeating units, it is classified as a crystalline
material. Crystalline solids are only produced when the atoms, ions, or
molecules have an opportunity to organize themselves into regular
arrangements, or lattices.
If there is no long-range structural order throughout the solid, the material is
best described as amorphous. Quite often, these materials possess considerable
short-range order over distances of 1–10 nm or so. However, the lack of
longrange translational order (periodicity) separates this class of materials
from their crystalline counterparts.
Two-dimensional illustrations of the structures of (a) crystalline
silica, (b) liquid or glassy silica and (c) glassy or vitreous silica
containing some sodium oxide
Microstructure
Single Crystals
Polycrystalline
 Periodic and repeated arrangement
of atoms is perfect or extends
through the entirety of the specimen
 Unit cells interlock in the same way
and have the same orientation
 Can be produced naturally and
artificially
 Difficult to grow, environment
must be tightly controlled
 Many small crystals or grains
 Small crystals misoriented with respect
to each other
 Several crystals are initiated and grow
towards each other
 Grain boundary: some atomic mismatch
within the region where two grains meet
Microstructure
Anisotropy: directionality of properties
Isotropic: properties independent of the direction of
measurement
Anisotropic
Having different physical and mechanical properties in
various directions. Anisotropy of single crystals is a
result of crystalline anisotropy, whereas that of a
polycrystal is dependent on crystallographic texture
(and so on the crystalline anisotropy) as well as on the
microstructural anisotropy as, e.g., banded structure
or carbide stringers in steels or an elongated grain
structure in heat-resistant alloys. Anisotropy can be
observed not only in crystalline solids but also in some
liquids.
Isotropic
Possessing mechanical or physical properties independent of or slightly dependent
on the direction in a sample. The observed isotropy in non-textured polycrystals is
macroscopic because it results from averaging the anisotropic properties of many
crystallites over the specimen volume. Thus, strictly speaking, nontextured
polycrystals are quasi-isotropic.
Composition, Bonding, Crystal Structure
and Microstructure DEFINE Materials Properties
Composition, Bonding, Crystal Structure
and Microstructure DEFINE Materials Properties
Aluminum oxide may be transparent, translucent, or opaque
depending on the material structure
single crystal
polycrystal:
low porosity
polycrystal:
high porosity
A better understanding of structure-composition-properties relations has
lead to a remarkable progress in properties of materials.
Example is the dramatic progress in the strength to density ratio of
materials, that resulted in a wide variety of new products, from dental
materials to tennis racquets.
QUESTIONS

İleri Kompozit Malzemeler

Transcription

Similar documents

Viva la Savings!

Our Family Happy Thanksgiving

29 April 2016

Auction - Ulmer Auctions

$299 $549 $559 $199 $499 $399 $129

Workshop on Case Method of Teaching at ICFAI University

ICU promo flyer final - Hospital zum Heiligen Geist Kempen

BEEPER_1981-01

Lil Rascals.indd