Introduction to Engineering Metallurgy

1. Engineering Metallurgy
Lecture I
 Materials Science & Engineering.
 Materials Performance.
 Classification of Materials.

2. Materials Science and Engineering
 Material science: the relation between the
structures and properties of materials.
 Material Engineering: the use of the material to
produce a predetermined set of properties.
Selecting the best material is usually a difficult task
Tradeoffs between different material
properties, including cost.

3. Properties: mechanical, physical, electrical, thermal,
magnetic, optical, deteriorative, production and
aesthetic.

4. Choose a material for a cup to
hold a liquid

6.  Performance
 Life and deterioration
 Cost
 Appearance
 Durability

7. Material selection
 High modulus.
 High yield strength
 Hard
 Tough

8. Material selection
 High modulus.
 Strong
 Hard
 Tough

9. Atomic Structure
 Atoms: nucleus, protons, neutrons, electrons.
 Electron configuration and the quantum
numbers.
 Atomic number.
 Atomic mass and Atomic mass unit.
 Valence electrons.

10. Periodic Table

11. Of the 106 elements:
 82 metals.
 18 nonmetals.
 6 metalloids.

12. Bonding Force and Energy
The net force between the two atoms:
Fn=Fa+Fr
At equilibrium:
Fa+Fr=0
The bonding energy for these
two atoms, E0, corresponds to
the energy at the minimum
point; it represents the energy
that would be required to
separate these two atoms to an
infinite separation.

13. Types of Bonding
 Primary Bonds
 Ionic bonding.
 Covalent bonding.
 Metallic bonding.
 Secondary Bonds
 Van der Walls (London, Dipole-Dipole) Bonding.
 Hydrogen bonding.

14. Ionic Bonds
•In compounds that are
composed of both metallic and
non metallic.
•The attractive bonding forces
are coulombic.
•Nondirectional: the magnitude
of the bond is equal in all
directions around an ion.
•Bonding energy (600-1500
kJ/mol) are relatively
large….High melting
temperatures.
•Ceramics.

15. Covalent Bonding
•Stable electron configurations are assumed by
the sharing of electrons between adjacent
atoms.
•Directional: between specific atoms and may
only exist only in direction between one atom
and another that participate in the electron
sharing.
•Silicate ceramics, glasses, diamond, polymers,
water.
•It is possible to have interatomic bonds that are
partially ionic and partially covalent, and in fact,
very few compounds exhibit pure ionic or
covalent bonding: the higher the difference in
electronegativity, the more ionic the bond, and
vice versa.

16. Metallic Bonding
•Valence electrons are not
bound to any particular atom
in the solid and are more or
less free to drift throughout
the entire metal forming a sea
of electrons or an electron
cloud.
•Energies range from
68 kJ/mol for mercury to
850 kJ/mol for Tungesten.
•For all elemental metals and
their alloys.

17. Van der Waals Bonding
•From atomic or
molecular dipoles.
•Coloumbic attraction
between the positive end
of one dipole and the
negative end of another.
•10 kJ/mol.

18. Hydrogen Bonding
•The hydrogen, less
electronegative than the
oxygen acquire a positive
charge.
•An attraction between
the positively charged
hydrogen and the
negatively charged
oxygen of another
molecule.
•Keeps water liquid at
room temperature.

19. Bonding energies and melting temperatures
for various substances
Bonding type Substance Bonding energy
(kJ/mol)
Melting
temperature (0C)
Ionic
NaCl 640 801
MgO 1000 2800
Covalent
Si 450 1410
C (diamond) 713 >3550
Metallic
Hg 68 -39
Al 324 660
Fe 406 1538
W 849 3410
Van der Waals
Ar 7.7 -189
Cl2 31 -101
Hydrogen
NH3 35 -78
H2O 51 0

20. Classification of Materials

21. Metals
 Solid at normal temperature (except Mercury).
 Large number of nonlocalized electrons.
 Good conductors of electricity and heat.
 Non transparent to visible light.
 Most metals are magnetic.
 Strong, yet deformable.

22.  Iron and steels
 Aluminium and its alloys
 Copper and its alloys
 Nickel and its alloys
 Titanium and its alloys

23. Ceramics
 Compounds between metallic and nonmetallic
elements.
 Most frequently: oxides, nitrides and carbides.
 Insulative and poor heat conductors.
 More resistant to high temperatures and hursh
environments than metals and polymers.
 Hard, but brittle.

24.  Alumina (Al2O3, emery, sapphire)
 Magnesia (MgO)
 Silicon carbide (SiC)
 Silicon nitride (Si3N4)
 Cement and concrete

25. Polymers
 Plastic and rubber materials.
 Many of them are organic compounds that are
based on carbon, hydrogen …
 Very large molecular structure.
 Low density and may be extremely flexible.

26.  Polyethylene (PE)
 Polymethylmethacrylate (PMMA)
 Polyamide (PA)
 Polystyrene (PS)
 Polyurethane (PU)
 Polyvinylchloride (PVC)
 Polyethylene tetraphthalate (PET)
 Polyethylether Ketone (PEEK)
 Epoxies (EP)
 Elastomers, such as natural rubber (NR)

27. Glasses
 What is a glass material:
super-cooled liquid.
(highly viscous)
 All of the above materials can be produced in a glassy
form (non crystalline) using fast cooling.

29. Composites
 An engineered material to display a combination
of the best characteristics of each of the
component materials.
 Glass Fibre Reinforced Polymer (GFRP):
Strength: glass fibre
flexibility: polymer matrix

31. New types of materials
 Semiconductors & Superconductors: it has
revolutionized our life.
 Biomaterials: must be compatible with body tissues and
not to produce toxic substances.
 Advanced Materials: materials for HiTec applications.
 Smart Materials: sensor – processor – actuator:
piezoelectric ceramics, magnetoresistive materials.
 Nanomaterials: design new materials built from simple
atomic level constituents – carbon nanotubes.

32. Crystalline vs. Amorphous
 A crystalline material is the one in which the
atoms are situated in a repeating or periodic
array over large atomic distances (long range
order).
 Amorphous solids lack a systematic and regular
arrangement of atoms over relatively large
atomic distances (non-crystalline, super-cooled
liquid).

33. Rapid cooling through the freezing temperature
favours the formation of a noncrystalline solid.

34.  Anistropy: directionality of properties.
 Substances in which measured properties are
independent of the direction of measurement
are termed isotropic.