TWO MARK QUESTION AND ANSWER UNIT I CONSTITUTION OF ALLOYS ...

TWO MARK QUESTION AND ANSWER

UNIT I

CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS

1. Define solid solution.

A solid solution may be defined as a solid that consists of two or more elements

automatically dispersed in a single-phase structure.

2. Differentiate substitutional and interstitial solid solutions.

Substitutional solid solution Interstitial solid solution

When the solute atoms substitute

for parent solvent atoms in a crystal In interstitial solid solution , the solute

lattice, are called substitutional atoms, atoms fit in to space between the

and the mixture of the two elements is solvent or parent atoms

called a substitutional solid solution

3. State Gibbs’s phase rule.

F=C–P+2

Where,

F = Degrees of freedom

C = number of components

P = number of phases present.

4. What is liquidus line?

Liquidus is the line or boundary that separates liquid and liquid + solid phase regions.

5. What is solidus line?

Solidus is the line or boundary that separates solid and solid + liquid phase regions.

6. What is solvus line?

Solvus is the line or boundary that separates single phase solid regions from two phase

solid regions.

7. Define triple point.

The point at which three phases (solid, liquid, and vapour) of a single material coexist is

called triple point.

8. What is an isomorphous system?

In some binary alloy systems, the two elements are completely soluble in each other in

both the liquid and solid states. In these systems only a single type of crystal structure exists

and therefore they are called isomorphous systems.

9. Define eutectic reaction.

Eutectic reaction is the reversible, isothermal reaction of a liquid which transforms in to

two different solid phases upon cooling.

The eutectic reaction can be written as

Cooling

Liquid Solid 1 + Solid 2

Heating

10. Define peritectic reaction.

Peritectic reaction is the reversible, isothermal reaction in which a solid and liquid phase

transform in to a solid phase upon cooling.

The peritectic reaction can be written as

Cooling

Liquid + Solid 1 Solid 2

Heating

11. Define eutectoid reaction.

Eutectoid reaction is the reversible, isothermal reaction in which one solid phase

transforms in to two mixed solid phases, upon cooling.

The eutectoid reaction can be written as

Cooling

Solid 1 Solid 2 +Solid 3

Heating

12. Define peritectoid reaction.

Peritectoid reaction is the reversible, isothermal reaction in which two solid phases

transform in to a third solid phase upon cooling.

The peritectoid reaction can be written as

Cooling

Solid 1 + Solid 2 Solid 3

Heating

13. Define the terms ‘ferrite’ and ‘austenite’ in iron carbon alloy system.

Ferrite is a primary solid solution based on α iron having BCC structure.

Austenite is a primary solid solution based on γ iron having FCC structure. Both are
interstitial solid solutions of carbon in iron.
14. What do you understand by the term ‘allotropy’?

Allotropy refers to the possibility of existence of two or more different crystal structures
for a substance depending upon temperature.
15. Write down the allotropy forms of pure iron.

α – iron (BCC structure, stable up to 912° C )
γ – iron (FCC structure, stable between 912° C to 1394° C )
δ – iron (BCC structure, stable between 1394° C to 1538 ° C )

16. Define polymorphism.
Allotropy refers to the possibility of existence of two or more different crystal structures

for a substance depending upon temperature. This phenomenon is also known as
polymorphism.
17. What is steel?

Steel is an alloy of carbon and iron, with 0.008 ℅ to 2 ℅ of carbon.
18. What is meant by eutectoid, hypo eutectoid, hyper eutectoid steel?

Steel contain 0.8℅ of carbon is called eutectoid steel.
Steels having less than 0.8℅ of carbon are known as hypo eutectoid steels.

Steels having above 0.8 ℅ of are known as hyper eutectoid steels.
19. What is cast iron?

Cast Iron is an alloy of carbon and iron, with above 2 ℅ of carbon in iron.
20. What is meant by eutectic, hypo eutectic, hyper eutectic cast iron?

Cast iron contain 4.3℅ of carbon is called eutectic cast iron.
Cast iron having less than 4.3℅ of carbon is known as hypo eutectic cast iron.
Cast iron having above 4.3 ℅ of carbon is known as hyper eutectic cast iron.

Unit II

HEAT TREATMENT

1. What is Heat treatment of metal?
a. It is the controlled heating and cooling of metals for the purpose of altering their
properties.

2. Write some objectives of Heat treatment?
a. To Relieve internal stresses
b. To improve Machinability
c. To improve the properties

3. What are the types of heat Treatment?
a. Annealing
b. Normalising
c. Hardening
d. Tempering

4. What are the types of Annealing?
a. Full
b. Stress-relief
c. Recrystallization
d. Spheroidizing
e. Process

5. What is the process in Full Annealing?
a. Heating the steel 15 0 to 40 0 C above critical temperature
b. Hold in that temperature for a period of time, now the steel is austenized
c. Cooling is done very slowly in the furnace itself.

6. What is the process in Stress relief annealing?
a. Heating the steel 550 to 650 0 C
b. Hold in that temperature for a period of time, now the steel is austenized
c. Cooled slowly

7. What is the process in Recrystallization or process annealing?
a. Heating the steel 550 to 650 0 C
b. Hold in that temperature for a period of time, now the steel is austenized, then
Cooled at any desired rate.

8. What is the Spheroidizing?
a. The cementite is hard to machine because of its needle like structure. So heated
to about 700°C.

b. Now the Cementite becomes globular structure called Spheroids which will be
easy to machine.

9. What is Normalising?
Similar to FullAnnealing but cooling established in still air called normalizing.
Heating the steel 50 to 600 C above critical temperature
Hold for a short time. Now the steel is Austenized
Cool down in still air

10 What is the purpose of normalizing?
To refine the grain size
To produce more uniform structure and desirable size distribution.

11 .What is TTT diagram?
TTT diagram is a plot of temperature versus the logarithm of time for a steel alloy of
definite composition.

12 .what are the other names of TTT diagram?
Isothermal Transformation(IT-diagram) curves and S-curve,C-curve, Bain’s curve due to
their shapes

13. what are the co-ordinates of IT-diagram?
Amount of Austenite transformed in vertical axis(Y-axis)
Time(Logirathamic scale,so we can use for days,weeks,months) in X-axis

14. What are the products you came to know from IT-diagram?
At 700 0 C Coarse Pearlite
At 600 0 C upper Bainite ( Sorbite )
At 500 to 550 0 C Fine Pearlite(Troosite)
At 550 to 300 0 C Lower Bainite (acicular troosite)

15.What is Hardness?
It is the property of a material by virtue of which it is able to resist abrasion, indentation
and scratching.

16.What is Hardening?
It refers to the heat treatment which increases the hardness by quenching.

17.What is the reason for Hardening?
Martensite is formed from Austenite directly .This is a complex structure formed due
to sudden cooling.

18.What is Critical Cooling Rate(CCR)?
The slowest rate of cooling of austenite that will result in 100% Martensite transformation
is known as the critical cooling rate

19.What is Tempering?
In Hardening the metal becomes too brittle and with lot of internal stresses which
would affect the property of metal. To remove this and to get desired property we
reheat the hardened metal. This process is called Tempering.

20.What is Martempering?
If we reheat the metal after Martensite formation is called martempering.

21.What is Austempering?
It is the quenching technique that the metal is quenched to the temp just above the
Martensite start(Ms) temp and keep that temp until complete transformation of
austenite to Bainite structure.

22.What is Martempering?

It is the quenching technique that the metal is reheated after Martensite formation

23.What are the three types of Tempering?
Low temperature
High temperature
Medium Temperature

24.What are the types of hardening process?
Work Hardening
Age Hardening
Air Hardening
Hardening by heating and quenching

25.What is Hardenability?
Ability of the metal to get hardened is known as Hardenability.

26.What is the test to find Hardenabilty?
Jominy End Quench Test

27.What are the various types of case Hardening?
Carburizing, Cyaniding, Nitriding, Flame and Induction Hardening

28.What is Nitriding?
It is the process of introducing nitrogen atoms to obtain hard surface of the steel
components.

29.What is Carbonitriding?
It is the process of introducing both carbon and nitrogen atoms to obtain hard surface of
thes teel components.

30.What is selective hardening technique?
It is the technique in which different properties are obtained simply by varying the
temperature of various regions.

31.What is Flame hardening?
It is a selective hardening process in which combustible gas flame is used as the source of
heat.

32.What is Induction hardening?
It is a selective hardening process using ‘resistance to induced eddy currents’ as the
source of heat.

SIX MARK QUESTIONS

UNIT I

CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS

1. What is allotropy? Explain the allotropic forms of pure iron.
2. List the micro constituents of iron carbon equilibrium diagram and

explain any one.
3. Explain the factors affecting solid solubility of a solution (or) Explain

Hume Rothery rules.
4. Explain about cooling curves.
5. Explain eutectic and eutectoid reactions.
6. Write short note about ferrite ,austenite, cemintite

UNIT II

HEAT TREATMENT

1 What is meant by Normalizing? List the objectives of normalizing
2. What is Austempering? Explain the Austempering process.
3. Explain the factors affecting hardness of a material.
4. Explain martempering.
5. Explain about cyaniding.
6. What are the purpose of heat treatment

TEN MARK QUESTIONS

UNIT I

CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS

1.Draw Iron-Iron carbide equilibrium diagram and mark on it all salient
temperatures and composition fields.
2. What is solid solution? Explain the type of solid solutions with sketch.
3. Explain the transformation of cast iron.
4. Explain the transformation of steel.
5. Explain the steps involved in phase diagram problems.

UNIT II

HEAT TREATMENT

1. Draw a neat sketch of the TTT diagram.

2. Draw CCT diagram for eutectoid steel which is superimposed on IT
diagram.
3. Explain the carbo nitriding process with neat sketch.
4. Define hardenability. Explain Jominy End-Quench Test.
5. Explain any one thermal method of surface hardening
6.Explain about various type of annealing