engineering metallurgy unit 1 question bank and model answers · prof. tushar a aneyrao unit i...

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



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.



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.



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.



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.



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)



2. Body Centered Cubic (BCC)

3. Face Centered Cubic (FCC)



Q04: Calculate the atomic packing factor for BCC and FCC

structure.(08marks)



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



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:



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.



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.



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:



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.



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.



The dislocation itself then is a linear defect in the direction into the paper.

Dislocations either terminate at the edge of the crystal (edge dislocation 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.



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



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



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



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.

engineering metallurgy unit 1 question bank and model answers · prof. tushar a aneyrao unit i...

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