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St. Vincent Pallotti College of Engineering and Technology, Nagpur
Prof. Tushar A Aneyrao Unit I Question Bank 1 | P a g e
Engineering Metallurgy
Unit 1
Question Bank and Model Answers
Q 01: Discuss Classification, properties & application of engineering materials in
detail. (07marks)
Engineering Materials
Metals
FerrousNon
Ferrous
Non metals
Ceramics Polymers Composites
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Metals
Metals are polycrystalline bodies which are having number of differentially oriented
fine crystals. Normally major metals are in solid states at normal temperature.
However, some metals such as mercury are also in liquid state at normal temperature.
All metals are having high thermal and electrical conductivity. All metals are having
positive temperature coefficient of resistance. Means resistance of metals increases
with increase in temperature.
Examples of metals – Silver, Copper, Gold, Aluminum, Iron, Zinc, Lead, Tin etc.
Metals can be further divided into two groups-
1. Ferrous Metals – All ferrous metals are having iron as common element. All
ferrous materials are having very high permeability which makes these materials
suitable for construction of core of electrical machines. Examples: Cast Iron,
Wrought Iron, Steel, Silicon Steel, High Speed Steel, Spring Steel etc.
2. Non-Ferrous Metals - All non-ferrous metals are having very low permeability.
Example: Silver, Copper, Gold, Aluminum etc.
Non-Metals
Non-Metal materials are non-crystalline in nature. These exists in amorphic or
mesomorphic forms. These are available in both solid and gaseous forms at normal
temperature. Normally all non-metals are bad conductor of heat and electricity.
Examples: Plastics, Rubber, Leathers, Asbestos etc. As these non-metals are having
very high resistivity which makes them suitable for insulation purpose in electrical
machines.
1. CERAMICS:
A particle or fibrous which are used in terms of making ceramic products. Ceramics
have regular atomic structure and crystal structure. Ceramics are mainly oxides,
nitrides and carbides. They are non conducting materials, due to its insulating
property they are used as insulators. They are very hard and brittle in nature.
Eg: alumina, silica, silicon carbide, diamond, bricks, etc.
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Applications:
Due to the compressive strength bricks are used in construction
Because of their good thermal insulation ceramic tiles are used in ovens.
Some ceramics are transparent to radar and other electromagnetic waves are
used in radomes and transmitters.
Glass ceramics have high temperature capabilities so they are used in optical
equipment and fiber insulation.
Alumina, silica, silicon carbide are used in making tools.
Diamond is used in ornaments and cutting tool applications.
2. POLYMERS:
Polymers have chain molecule structure of carbon as back bone atoms. They are
mainly made up of tough organic materials. They are low density materials and also
flexible. In some cases polymers are not flexible.
Polymers are not only used as structural materials, they can be used as fiber and
resins in the matrix of composite materials.
Eg : polyester as fibers, phenolics and epoxides as resins.
Elastomers are also polymers but they are considered separately due to their specific
design for certain purposes like shock and vibration absorption.
Natural polymers :
Eg : wool, silk, DNA, cellulose, proteins, etc.
Synthetic polymers:
Thermo plastics
Thermosetting plastics
Eg: nylon, polyethylene, polyester, Teflon, epoxy, Bakelite, etc.
Applications:
Polyethylene is used for making carry bags.
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Polypropylene is used for making high temperature resistance products like
feeding bottle.
Polyether ether ketone and polyethylene ketone are used in mineral water
bottle concept.
Poly carbonate is used to make high performance polymers like transparent
polymers
Polyaniline is a conducting polymer.
Bakelite used for making insulating materials.
3. COMPOSITE:
Composite material is the composition of two or more constituent materials with
different physical and chemical properties to produce a different characteristic
material.
Composite material may be both metals or metal and ceramic or metal and polymer,
depending upon the application requirement the combination is made.
Eg : wood, concrete, fiber glass, CFRP (carbon fiber reinforced plastic), GFRP (glass
fiber reinforced plastic), etc.
Applications:
CFRP and GFRP are used for automotive body parts.
CRPF and honeycomb composites are used for chassis.
Some fuel tanks are made up of Kevlar reinforced fiber.
Reinforced thermosets are used in springs and bumper system.
Fibreglass reinforced plastic has been used for boat hulls, fishing rods, tennis
rackets, helmets, bows and arrows.
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Q 02: Calculate atomic packing factor for FCC Crystal Structure. (07marks)
Face Centered Cubic : An arrangement of atoms in crystals in which the atomic
centers are disposed in space in such a way that one atom is located at each of the
corners of the cube and one at the center of each face. This structure also contains
the same particles in the centers of the six faces of the unit cell, for a total of 14
identical lattice points.The face-centered cubic unit cell is the simplest repeating unit
in a cubic closest-packed structure.
The atomic packing factor [A.P.F]:
It can be defined as the ratio between the volume of the basic atoms of the
unit cell (which represent the volume of all atoms in one unit cell ) to the
volume of the unit cell it self.
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Q03: Define the terms a)Space Lattice b) Unit Cell. Name important crystal
structure for metals, Draw neat sketch of any one. (06 marks)
A) Space lattice: In a solid crystalline material, the atoms or molecules are
arranged regularly and periodically in three dimensions. To explain crystal
symmetries easily, it is convenient to represent an atom or a group of atoms
that repeats in three dimensions in the crystal as a unit. If each such unit of
atoms or atom in a crystal is replaced by a point in space, then the resultant
points in space are called space lattice. Each point in space is called a lattice
point and each unit of atoms or atom is called basis or pattern. A space lattice
represents the geometrical pattern of crystal in which the surroundings of each
lattice point is the same.
If the surroundings of each lattice point is same or if the atom or all the atoms
at lattice points are identical, then such a lattice is called Bravais lattice. On
the other hand, if the atom or the atoms at lattice points are not same, then it
is said to be a non-Bravais lattice.
B) Unit Cell: Unit cells for most of the crystals are parallelopipeds or cubes
having three sets of parallel faces. A unit cell is the basic structural unit or
building block of the crystal. A unit cell is defined as the smallest
parallelopiped volume in the crystal, which on repetition along the
crystallographic axes gives the actual crystal structure or the smallest
geometric figure, which on repetition in three-dimensional space, gives the
actual crystal structure called a unit cell. The choice of a unit cell is not unique
but it can be constructed in a number of ways.
Following are the important unit cells in a crystal Lattice
1. Simple Cubic (SC)
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2. Body Centered Cubic (BCC)
3. Face Centered Cubic (FCC)
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Q04: Calculate the atomic packing factor for BCC and FCC
structure.(08marks)
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Q 05: Differentiate between microscopic and macroscopic examination of
materials. (04 marks)
Macroscopic Examination Microscopic Examination
1 Involves the study of the metal
structure & their alloys by naked
eye or by low power
magnification up to 15X. & the
observed structure is called
macrostructure.
1 Involves the study of the metal
structure & their alloys under
microscope at magnification from
20X to 2000X & the observed
structure is called microstructure.
2 Involves much smaller areas &
brings out information which can
never be revealed by macro
examination. Gives broad picture
of the interior of a metal by
studying relatively large
sectioned area
2 Magnification on a microscope
refers to the amount or degree to
which the object observed is
enlarged. It is measured by
multiples, such as 2x, 4x and 10x,
indicating that the object is
enlarged to twice as big, four times
as big or 10 times as big,
respectively
3 AIM :
To reveal the size, form & arrangement of crystallites
in cast metals.
To reveal cracks appearing during certain fabrication
processes.
To reveal fibers in deformed metals.
To reveal shrinkage porosity & gas cavities.
To find cause of failure of a component part.
3 AIM :
To determine chemical content of alloy
To discover micro defects
To Reveal structures characteristic
To determine the size & shape of the crystallites
To indicate quality of Heat treatment etc…..
4 Need not be taken to such a high
degree of surface finish & so the
final stages of polishing can be
omitted.
4 Requires proper surface
preparation of the specimen. Final
stage of polishing is requires
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Q 06: What is plastic deformation? Explain Slip mechanism in detail with
suitable sketch. (06 marks)
Plastic deformation is accompanied by changed in both internal & external state and
it is not reversible. Permanent deformation involves distortion of the crystal &
microstructure. It carried out as in working and shaping processes such as bending,
stamping, drawing, spinning, rolling, forging, Extruding etc. The stamping of
automobile parts, pressing of ship shafting, spinning of Al pans, rolling of boiler
plates, rails, I beams, drawing of wire, extension of telephone cables & forging of
crankshaft all operations involve plastic deformation of metals & alloys.
Plastic deformation by Slip:
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Slip is defined as that mechanism of deformation where in one part of
the crystal moves/ slips over another part along certain planes known as slip
plane. Slip due to pure shearing stresses that are acting across the specimen
irrespective of whether the crystal is subjected to tensile/ compressive
stresses.
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Slip is governed by the following major rules:
1. It occurs only along certain crystallograpohic planes and directions
2. Slip occurs only along the most closely packed set of planes
3. Slip direction is that direction on when the atoms are most closely
spaced. Slip occurs on that system where the shear stress is maximum
i.e., at 45o to the applied tensile load.
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Q 07: Explain the concept of slip and twinning with related to plastic
deformation. (05marks)
For slip answer refer to above explanation
Plastic deformation by twining:
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In twinning each plane of atoms move through a definite distance and in the same
direction. The extent of movement of each plane is proportional to its distance from
the twining plane, as shown in fig. The distance moved by each successive atomic
plane is greater than the previous plane by a few atomic spacings. When a shear
stress is applied the crystal will twin about the twinning plane in such a way that the
region to the left of the twinning plane is not deformed where as the region to the
right is deformed. The atomic arrangement on either side of the twinned plane is in
such a way they are mirror reflections of each other. Twins are known as anneling
twins when they are produced during annealing heat treatment and mechanical twins
when they are produced by mechanical deformation of metals.
Mechanism of twinning:
Partial dislocation line moves up (or) down by one plane each time the twinning
dislocation goes round it. Twinning may be caused by impact, by thermal treatment
(or) by plastic deformation.
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Q 08: Explain in brief various imperfection found in crystal structure.
(07marks)
Any irregularity in the crystal structure is known as crystal imperfection or crystal
defects.
Defects can be classified as:
1. Points defects (Zero dimensional defects):
A point defect in a crystal is an entity that causes an interruption in the lattice
periodicity. This can occur due to many events.
If an atom is removed from its regular lattice site; the defect is a vacancy.
If an atom is in a site different from a regular lattice (substitutional) lattice
site; the defect is an interstitial. An interstitial defect can be of the same
species as the atoms of the lattice (it is an intrinsic defect, the self-interstitial)
or of a different nature (it is then an extrinsic defect, an interstitial impurity).
An impurity can occupy a substitutional site.
Anything other than a silicon atom on crystal lattice constitutes a Point defect.
Crucial role in diffusion & ion implantation and very less in oxidation
kinetics.
2. Line defects (One dimensional defects):
One-dimensional defects in crystals are known as dislocations. The crystal
contains an extra plane of atoms, which terminates at a dislocation.
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The dislocation itself then is a linear defect in the direction into the paper.
Dislocations either terminate at the edge of the crystal (edge dis- location or
they form a closed loop within the crystal (dislocation loops).
Dislocations are active defects in crystals, i.e. they can move when subjected
to stresses or when excess point defects are present. The process of "climb"
occurs when excess point defects are absorbed by the dislocation.
3. Surface or plane defects (Two dimensional defects):
The most common kind of 2D or area defect found in silicon is the stacking
fault.
Stacking faults always forms along {111} planes and are simply the insertion
or removal of an extra {111} plane.
In a perfect crystal, the stacking order is ABCABC, and so on. When a
stacking fault is present, either an extra plane is inserted (ABCACBC, etc.) or
a plane is missing (ABCABABC, etc.).
Such faults are referred to as "extrinsic" if there is an extra plane of atoms, or
"intrinsic" if a plane is missing.
Stacking faults are bounded by dislocations and, when they intersect the wafer
surface, are usually referred to as surface stacking faults.
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4. Volume defects (Three dimensional defects):
Volume or Bulk defects occur on a much bigger scale than the rest of crystal
defects.
Void is a common bulk defect. Voids are regions where there is large number
of atoms missing from the lattice.
When void occur due to air bubbles becoming trapped when a material
solidifies, it is commonly called porosity.
When a void occurs due to shrinkage of a material as it solidifies, it is called
cavitation.
Q 9: Differentiate between metal and non metal in brief with application.
(07marks)
Metals
Most elements are metals. This includes the alkali metals, alkaline earth metals,
transition metals, lanthanides, and actinides. On the periodic table, metals are
separated from nonmetals by a zig-zag line stepping through carbon, phosphorus,
selenium, iodine, and radon. These elements and those to the right of them are
nonmetals. Elements just to the left of the line may be termed metalloids or
semimetals and have properties intermediate between those of the metals and
nonmetals. The physical and chemical properties of the metals and nonmetals may
be used to tell them apart. Zinc Dust manufacturer in India
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Metal Physical Properties:
Lustrous (shiny)
Good conductors of heat and electricity
High melting point
High density (heavy for their size)
Malleable (can be hammered)
Ductile (can be drawn into wires)
Usually solid at room temperature (an exception is mercury)
Metal Chemical Properties:
Have 1-3 electrons in the outer shell of each metal atom and lose electrons
readily
Corrode easily (e.g., damaged by oxidation such as tarnish or rust)
Lose electrons easily
Form oxides that are basic
Fave lower electronegativities
Are good reducing agents
Nonmetals
Nonmetals, with the exception of hydrogen, are located on the right side of the
periodic table. Elements that are nonmetals are hydrogen, carbon, nitrogen,
phosphorus, oxygen, sulfur, selenium, all of the halogens, and the noble gases.
Nonmetal Physical Properties:
Not lustrous (dull appearance)
Poor conductors of heat and electricity
Nonductile solids
Brittle solids
Maybe solids, liquids or gases at room temperature
Transparent as a thin sheet
Nonmetals are not sonorous
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Nonmetal Chemical Properties:
Usually, have 4-8 electrons in their outer shell
Readily gain or share valence electron
Form oxides that are acidic
Have higher electronegativities
Are good oxidizing agents
BASIS FOR COMPARISON
METALS NON-METALS
Meaning Metals refers to the natural elements that are hard, shiny, opaque and dense.
Non-metals implies those chemical substances that are soft, non-shiny, transparent and brittle.
Example
Nature Electropositive Electronegative
Structure Crystalline Amorphic
Physical State at room temperature
Solid (except mercury and gallium)
Solid or gas (except Bromine)
Density High density Low density
Appearance Lustrous Non-lustrous
https://keydifferences.com/wp-content/uploads/2017/01/metal.jpghttps://keydifferences.com/wp-content/uploads/2017/01/non-metal.jpg
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BASIS FOR COMPARISON
METALS NON-METALS
Hardness Most metals are hard, except sodium.
Most metals are soft, except diamond.
Malleability Malleable Non-malleable
Ductility Ductile Non-ductile
Sonorous Sonorous Non-sonorous
Conduction Good conductor of heat and electricity
Poor conductor of heat and electricity
Melting and Boiling point
Very high melting and boiling point.
Low melting and boiling point.
Electrons 1 to 3 electrons in the outer shell.
4 to 8 electrons in the outer shell.
Oxygen React with oxygen and form basic oxides.
React with oxygen and form acidic oxides.
Acid React with acids and produce hydrogen gas.
Do not usually react with acids.
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