1. The percentage of carbon at eutectoid point in Fe-C phase diagram is?
a) 2.1
b) 4.3
c) 0.83
d) 0.02
Explanation: During cooling, austenite of 0.77% C, at a temeprature 725oC undergoes eutectoid transformation and forms a eutectoid a mixture of ferrite and cementite, known as pearlite.
2. The percentage of carbon at peritectic point in Fe-C phase diagram is?
a) 2.1
b) 4.3
c) 0.83
d) 0.18
Explanation: Percentage of carbon at peritectic point = 0.18%. Peritectic reaction in iron-carbon phase diagram takes place at constant temperature of 1493oC.
3. Which of the following reaction does not exhibit mushy zone in Fe-C phase diagram?
a) Eutectic reaction
b) Peritectic reaction
c) Eutectoid reaction
d) Peritectoid reaction
Explanation: A mushy zone is nothing but a solid-liquid mix in a two-phase region. The alloys or reactions, which exhibits lower melting points than the two pure metals are known as eutectic alloy systems taking eutectic reaction does not exhibit mushy zone.
4. γ form of iron is?
a) Magnetic
b) Non magnetic
c) Occurs below 768
d) Occurs above 1410oC
Explanation: γ form of iron is known as austenite (named after ‘Sir Austin), which is an interstitial solid solution of carbon in FCC iron. Austenite is soft, ductile, tough, malleable and non-magnetic.
5. Which of the following equation represents the Gibbs phase rule?
a) F = C + P + 2
b) F = C – P + 2
c) F = C + P + 1
d) F = C + P – 1
Explanation: The Gibbs phase rule is represented as: F = C – P + 2, where F = number of intensive degrees of freedom, P = number of phases and C = minimum number of independent constituents.
6.Number of degrees of freedom at a triple point in unary phase diagram is?
a) 1
b) 10
c) 0
d) -1
Explanation: A unary phase diagram has a single component thus, at triple point, the number of degrees of freedom, according to Gibbs phase rule F = 1 – 3 + 2 = 0.
7. The invariant reaction involving, a liquid phase decomposing into two different solids on cooling is known as _________
a) Eutectoid point
b) Eutectic point
c) Peritectic point
d) Peritectoid point
Explanation: The eutectic invariant reaction in general can be represented as:
L \(_{\overrightarrow{Cooling}}\) S1 + S2
where, L represent the liquid of eutectic composition and S1 and S2 are two different solids of fixed composition each.
8. The invariant reaction involving a solid phase decomposing into two different solids on cooling is known as ____________
a) Eutectoid point
b) Eutectic point
c) Peritectic point
d) Peritectoid point
Explanation: The eutectoid invariant reaction is a solid-state version of the eutectic reaction and in general, can be represented by an equation:
S1 \(_{\overrightarrow{Cooling}}\) S2 + S3
where, S1, S2 and S3 are three different solids each of fixed composition.
9. The invariant reaction involving a liquid phase and a solid phase changing into a single solid phase on cooling is known as ____________
a) Eutectoid point
b) Eutectic point
c) Peritectic point
d) Peritectoid point
Explanation: A peritectic reaction in general can be represented by an equation:
L + S1 \(_{\overrightarrow{Cooling}}\) S2
where, L represents a liquid of fixed composition, S1 and S2 are two different solids of fixed composition each.
10. The invariant reaction involving two solid phases changing into a single solid phase on cooling is known as ___________
a) Eutectoid point
b) Eutectic point
c) Peritectic point
d) Peritectoid point
Explanation: The peritectoid invariant reaction is a solid-state version of the peritectic reaction and in general, can be represented by an equation:
S1 + S2 \(_{\overrightarrow{Cooling}}\) S3
where, S1, S2 and S3 are three different solids each of fixed composition.