Classification of materials, Basic Metals & Alloys their properties and Applications Properties of Materials

1. Engineering Materials

2. Content
• Basic Metals & Alloys: properties and Applications: Properties
of Materials(Strength, elasticity, stiffness, malleability, ductility,
brittleness, toughness and hardness, Elementary ideas of
fracture, fatigue & creep.)

4. Historical Perspective
• Materials are so important in the
development of human civilization that the
historians have identified early periods of
civilization by the name of most significantly
used material, e.g.: Stone Age, Bronze Age.
• It is obvious that materials have affected and
controlling a broad range of human activities
through thousands of decades.

5. Contd…
• Human civilization started with Stone Age where
people used only natural materials, like stone, clay,
skin, and wood for the purposes like to make weapons,
instruments, shelter, etc.
• The increasing need for better quality tools brought
forth exploration that led to Bronze Age, followed by
Iron Age. When people found copper and how to make
it harder by alloying, the Bronze Age started about
3000 BC. The use of iron and steel, a stronger material
that gave advantage in wars started at about 1200 BC.

6. Contd…
• The next big step in human civilization was the
discovery of a cheap process to make steel around 1850
AD, which enabled the railroads and the building of the
modern infrastructure of the industrial world. One of
the most significant features of the democratic material
is that number of users just exploded.
• It’s being said and agreed that we are presently in
Space Age marked by many technological developments
towards development materials resulting in stronger
and light materials like composites, electronic materials
like semiconductors, materials for space voyage like
high temperature ceramics, biomaterials, etc.

7. Contd….
Each age is marked by the advent of certain
materials.
• The Iron Age brought tools and utensils.
• The Steel Age brought railroads, instruments, and
the Industrial Revolution.
• The Space Age brought the materials for stronger
and light structures (e.g., composite materials).
• The Electronic Age brought semiconductors, and
thus many varieties of electronic gadgets.

11. Why Study Materials Science and
Engineering?
It is vital that the professional engineer should know how
to select materials which best fit the demands of the
design - economic and aesthetic demands, as well as
demands of strength and durability. Beforehand the
designer must understand the properties of materials, and
their limitations.
• To select a material for a given use based on considerations
of cost and performance.
• To understand the limits of materials and the change of
their properties with use.
• To be able to create a new material that will have some
desirable properties.
• To be able to use the material for different application.

12. Mechanical Properties
• Hardness
• Brittleness
• Ductility
• Malleability
• Elastic Deformation
• Strain
• Stress
• Modulus of Elasticity
• Plastic Deformation
• Poisson’s Ratio
• Proportional Limit
• Tensile Strength
• Toughness
• Yielding
• Yield Strength
• Fatigue
• Creep
• Stiffness
• Strength
• Machinability
• Formability
• Weldability

20. Brittleness
• Brittleness of a material indicates that how easily
it gets fractured when it is subjected to a force or
load.
• When a brittle material is subjected to a stress it
observes very less energy and gets fractures
without significant strain.
• Brittleness is converse to ductility of material.
Brittleness of material is temperature dependent.
Some metals which are ductile at normal
temperature become brittle at low temperature.

21. Ductility
• Ductility is a property of a solid material which
indicates that how easily a material gets
deformed under tensile stress.
• Ductility is often categorized by the ability of
material to get stretched into a wire by pulling or
drawing.
• This mechanical property is also an aspect of
plasticity of material and is temperature
dependent. With rise in temperature, the
ductility of material increases.

22. Malleability
• Malleability is a property of solid materials which
indicates that how easily a material gets
deformed under compressive stress.
• Malleability is often categorized by the ability of
material to be formed in the form of a thin sheet
by hammering or rolling.
• This mechanical property is an aspect of plasticity
of material.
• Malleability of material is temperature
dependent. With rise in temperature, the
malleability of material increases.

23. Elastic deformation
• When the stress is removed, the material
returns to the dimension it had before the
load was applied.

24. Engineering Strain
• There is a change in dimensions, or
deformation elongation, đL as a result of a
tensile or compressive stress. To enable
comparison with specimens of different
length, the elongation is also normalized, this
time to the length L. This is called strain, e.
• It is the deformation of material due to stress
• e = đL/L

27. Engineering Stress
• In solid mechanics, stress is a physical quantity
that express the internal force per unit area
that neighboring particles of a continuous
material exert on each other.
• Resistance against deformation.

37. Poisson’s ratio
• Materials subject to tension shrink laterally.
Those subject to compression, bulge. The ratio
of lateral and axial strains is called the
Poisson's ratio n.
• n = elateral/eaxial
• The elastic modulus, shear modulus and
Poisson's ratio are related by E = 2G(1+n)

38. Modulus of Elasticity
• In tensile tests, if the deformation is elastic,
the stress strain relationship is called Hooke's
law:
• s = E e
• That is, E is the slope of the stress-strain curve.
E is Young's modulus or modulus of elasticity.

40. Yield point
• Yield point. If the stress is too large, the strain deviates
from being proportional to the stress. The point at
which this happens is the yield point because there the
material yields, deforming permanently (plastically).
• Yield stress. Hooke's law is not valid beyond the yield
point. The stress at the yield point is called yield stress,
and is an important measure of the mechanical
properties of materials. In practice, the yield stress is
chosen as that causing a permanent strain of 0.002
• The yield stress measures the resistance to plastic
deformation.

41. Tensile strength
• When stress continues in the plastic regime, the
stress-strain passes through a maximum, called
the tensile strength (sTS) , and then falls as the
material starts to develop a neck and it finally
breaks at the fracture point .
• Note that it is called strength, not stress, but the
units are the same, MPa.
• For structural applications, the yield stress is
usually a more important property than the
tensile strength, since once the it is passed, the
structure has deformed beyond acceptable limits.

42. Toughness
• It is the ability of a material to absorb the energy and
gets plastically deformed without fracturing. Its
numerical value is determined by the amount of
energy per unit volume. Its unit is Joule/ m3.
• For good toughness, materials should have good
strength as well as ductility.
• For example: brittle materials, having good strength
but limited ductility are not tough enough. Conversely,
materials having good ductility but low strength are
also not tough enough. Therefore, to be tough, a
material should be capable to withstand both high
stress and strain.

43. Yielding
• For structural applications, the yield stress is
usually a more important property than the
tensile strength, since once the it is passed,
the structure has deformed beyond
acceptable limits.

44. Fatigue
• Fatigue is the weakening of material caused by the
repeated loading of the material.
• When a material is subjected to cyclic loading, and
loading greater than certain threshold value but
much below the strength of material (ultimate
tensile strength limit or yield stress limit),
microscopic cracks begin to form at grain
boundaries and interfaces. Eventually the crack
reaches to a critical size.
• This crack propagates suddenly and the structure
gets fractured. The shape of structure affects the
fatigue very much. Square holes and sharp corners
lead to elevated stresses where the fatigue crack
initiates.

45. Creep
• Creep is the property of a material which
indicates the tendency of material to move slowly
and deform permanently under the influence of
external mechanical stress.
• It results due to long time exposure to large
external mechanical stress with in limit of
yielding.
• Creep is more severe in material that are
subjected to heat for long time. Slip in material is
a plane with high density of atoms.

46. Stiffness
• Ability of an object to resist deformation in
response to an applied force; rigidity; opposite
to flexibility

47. Strength
• It is the property of a material which opposes
the deformation or breakdown of material in
presence of external forces or load.
• Materials which we finalize for our
engineering products, must have suitable
mechanical strength to be capable to work
under different mechanical forces or loads.

48. Resilience
• Capacity to absorb energy elastically. The energy per unit
volume is the area under the strain-stress curve in the
elastic region.
• Resilience is the ability of material to absorb the energy
when it is deformed elastically by applying stress and
release the energy when stress is removed.
• Proof resilience is defined as the maximum energy that
can be absorbed without permanent deformation.
• The modulus of resilience is defined as the maximum
energy that can be absorbed per unit volume without
permanent deformation. It can be determined by
integrating the stress-strain cure from zero to elastic
limit. Its unit is joule/m3.

49. WELDING
• Welding is a materials joining process which
produces coalescence of materials by heating them
to suitable temperatures with or without the
application of pressure or by the application of
pressure alone, and with or without the use of filler
material.

50. WELDABILITY
• The weldability, also known as joinability, of a
material refers to its ability to be welded.
Many metals and thermoplastics can be welded,
but some are easier to weld than others. A
material's weldability is used to determine the
welding process and to compare the final weld
quality to other materials.

51. Forming
Large group of manufacturing processes in
which plastic deformation is used to change
the shape of metal workpieces
• The tool, usually called a die, applies stresses
that exceed the yield strength of the metal
• The metal takes a shape determined by the
geometry of the die

53. Formability
• Formability is the ability of a
given metal workpiece to undergo plastic
deformation without being damaged. The
plastic deformation capacity
of metallic materials, however, is limited to a
certain extent, at which point, the material
could experience tearing or fracture
(breakage).

54. Machining
• Machining is a process in which a material (often
metal) is cut into a desired final shape and size by a
controlled material-removal process. The processes
that have this common theme, controlled material
removal, are today collectively known as subtractive
manufacturing, in distinction from processes of
controlled material addition, which are known
as additive manufacturing.
• Machining is a part of the manufacture of
many metal products, but it can also be used on
materials such as wood, plastic, ceramic,
and composites.

57. • Properties, Composition, and Industrial
Applications of materials: metals (ferrous- cast
iron, tool steels, stainless steels and non-
ferrous - Aluminum, brass, bronze ),

58. Classification of Materials

59.  Two important contributing factors to the properties of materials is the nature of bonding
and the atomic structure.
 Both of these are a result of electron interactions and resulting distribution in the material.
 Note: the energies listed in the table below are approximate.
Effect of Bonding on properties: a broad flavour
Bond
Bond
Energy eV
Melting
point
Hardness
(Ductility)
Electrical
Conductivity
Examples
Covalent ~1-10 High Hard (poor) Usually Low
Diamond, Graphite,
Ge, Si
Ionic ~5-15 High Hard (poor) Low NaCl, ZnS, CsCl
Metallic ~0.5-8 Varies Varies High Fe, Cu, Ag
Van der
Waals
~0.05-0.5 Low Soft (poor) Low Ne, Ar, Kr
Hydrogen ~0.05-1.5 Low Soft (poor) Usually Low Ice
* For comparison thermal energy at RT (300K) is 0.03 eV
(Note: 1eV = 1.6021019)

60. Various Properties of Materials
• All important properties of solid materials may be grouped as:
Mechanical, Electrical, Thermal, Magnetic, Optical, Deteriorative.
For each there is a characteristic type of stimulus capable of
provoking different response.

61. Metals
• These materials are characterized by high thermal and
electrical conductivity; strong yet deformable under
applied mechanical loads; opaque to light (shiny if
polished). These characteristics are due to valence
electrons that are detached from atoms, and spread in
an electron sea that glues the ions together, i.e. atoms
are bound together by metallic bonds and weaker van
der Waalls forces. Pure metals are not good enough for
many applications, especially structural applications.
Thus metals are used in alloy form i.e. a metal mixed
with another metal to improve the desired qualities.
E.g.: aluminum, steel, brass, gold.

64. polymers (natural and synthetic , thermoplastic and
thermosetting), ceramics (glass, optical fiber glass,
cements), composites ( fiber reinforced, metal matrix),
smart materials (piezoelectric, shape memory, thermo
chromic, photochromic, magneto rheological), Conductors,
Semiconductors and insulators, Organic and Inorganic
materials. Selection of Materials for Engineering
Applications.

65. Ceramics
• These are inorganic compounds, and usually made
either of oxides, carbides, nitrides, or silicates of
metals.
• Ceramics are typically partly crystalline and partly
amorphous. Atoms (ions often) in ceramic materials
behave mostly like either positive or negative ions, and
are bound by very strong Coulomb forces between
them.
• These materials are characterized by very high strength
under compression, low ductility; usually insulators to
heat and electricity. Examples: glass, porcelain, many
minerals.

67. Polymers
• Polymers in the form of thermo-plastics (nylon, polyethylene,
polyvinyl chloride, rubber, etc.) consist of molecules that have
covalent bonding within each molecule and van der Waals forces
between them.
• Polymers in the form of thermo-sets (e.g., epoxy, phenolics, etc.)
consist of a network of covalent bonds. They are based on H, C
and other non-metallic elements.
• Polymers are amorphous, except for a minority of
thermoplastics. Due to the kind of bonding, polymers are
typically electrical and thermal insulators. However, conducting
polymers can be obtained by doping, and conducting polymer-
matrix composites can be obtained by the use of conducting
fillers. They decompose at moderate temperatures (100 – 400
C), and are lightweight. Other properties vary greatly.

69. Composite materials
• Composite materials are multiphase materials obtained by artificial
combination of different materials to attain properties that the
individual components cannot attain.
• An example is a lightweight brake disc obtained by embedding SiC
particles in Al-alloy matrix. Another example is reinforced cement
concrete, a structural composite obtained by combining cement
(the matrix, i.e., the binder, obtained by a reaction known as
hydration, between cement and water), sand (fine aggregate),
gravel (coarse aggregate), and, thick steel fibers.
• However, there are some natural composites available in nature, for
example – wood. In general, composites are classified according to
their matrix materials. The main classes of composites are metal-
matrix, polymer-matrix, and ceramic-matrix.

70. •Poly-paraphenylene terephthalamide (K29) – branded Kevlar
•Kevlar is a heat-resistant and strong synthetic fiber
•Kevlar has many applications, ranging from bicycle tires and racing sails to bulletproof vests, all
due to its high tensile strength-to-weight ratio; by this measure it is five times stronger than
steel.

71. Semiconductors
• Semiconductors are covalent in nature. Their atomic structure
is characterized by the highest occupied energy band (the
valence band, where the valence electrons reside
energetically) full such that the energy gap between the top
of the valence band and the bottom of the empty energy
band (the conduction band) is small enough for some fraction
of the valence electrons to be excited from the valence band
to the conduction band by thermal, optical, or other forms of
energy.
• Their electrical properties depend extremely strongly on
minute proportions of contaminants. They are usually doped
in order to enhance electrical conductivity. They are used in
the form of single crystals without dislocations because grain
boundaries and dislocations would degrade electrical
behavior. They are opaque to visible light but transparent to
the infrared. Examples: silicon (Si), germanium (Ge), and
gallium arsenide (GaAs, a compound semiconductor).

72. Biomaterials
• These are any type material that can be used for
replacement of damaged or diseased human body
parts.
• Primary requirement of these materials is that they
must be biocompatible with body tissues, and must not
produce toxic substances.
• Other important material factors are: ability to support
forces; low friction, wear, density, and cost;
reproducibility.
• Typical applications involve heart valves, hip joints,
dental implants, intraocular lenses. Examples: Stainless
steel, Co-28Cr-6Mo, Ti-6Al-4V, ultra high molecular
weight poly-ethelene, high purity dense Al-oxide, etc

73. Contd….
• Among the cobalt chromium based alloys, the Co-28Cr-
6Mo (also termed ASTM F75) is the most applied alloy on
the biomedical field over the last decades.
• This alloy shows a good combination of mechanical
strength, fatigue and wear resistance, corrosion resistance
and biocompatibility
• Ti-6Al-4V (UNS designation R56400), also sometimes
called TC4, Ti64, or ASTM Grade 5, is an alpha-
beta titanium alloy with a high specific strength and
excellent corrosion resistance.
• It is one of the most commonly used titanium alloys and is
applied in a wide range of applications where low density
and excellent corrosion resistance such as aerospace
industry and biomechanical applications (implants).