Question 1
Iron-Carbon phase diagram is a ___________
A. Unary phase diagram
B. Binary phase diagram
C. Tertiary phase diagram
D. Ternary phase diagram
View Answer
Answer: Option B
Explanation:
Binary phase diagrams are based on two component systems. Here, the two components may be mixed in an infinite number of different proportions, which indicates that composition also becomes a variable, along with pressure and temperature. Iron-carbon phase diagram, Pb-Sn diagram are the best examples of this category.
Question 2
The melting point of iron (in oC) is?
A. 768
B. 1535
C. 1410
D. 910
View Answer
Answer: Option B
Explanation:
Melting point of iron in degree centigrade is 1535oC.
Question 3
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
View Answer
Answer: Option C
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.
Question 4
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
View Answer
Answer: Option D
Explanation:
Percentage of carbon at peritectic point = 0.18%. Peritectic reaction in iron-carbon phase diagram takes place at constant temperature of 1493oC.
Question 5
The temperature (in oC) of eutectic reaction in iron-carbon phase diagram is?
A. 1539
B. 1493
C. 910
D. 1150
View Answer
Answer: Option D
Explanation:
The invariant eutectic reaction (while cooling) in Fe-C phase diagram is given by:L (4.3%C) \(_{\overrightarrow{1150^o C}}\) γ (FCC, 2.11%C) + Cementite (Orthorhombic, 6.67%C)
Question 6
The temperature (in oC) of eutectoid reaction in iron-carbon phase diagram is?
A. 1120
B. 725
C. 910
D. 820
View Answer
Answer: Option B
Explanation:
The invariant peritectoid reaction (while cooling) in Fe-C phase diagram is given byγ (FCC, 0.77%C) \(_{\overrightarrow{725^o C}}\)Ferrite (BCC, 0.02%C)+ Cementite (Orthorhombic, 6.67%C).
Question 7
The temperature (in oC) of peritectic reaction in iron-carbon phase diagram is?
A. 1539
B. 1493
C. 910
D. 1175
View Answer
Answer: Option B
Explanation:
The invariant peritectic reaction (while cooling) in Fe-C phase diagram is given by:L (0.53%C) + δ-ferrite (BCC, 0.09%C) \(_{\overrightarrow{1493^o C}}\) γ (FCC, 0.17%C)
Question 8
Which of the following material has the carbon varying from 2.1 to 4.3%?
A. Dead steel
B. Mild steel
C. Medium carbon steel
D. Cast iron
View Answer
Answer: Option D
Explanation:
Cast irons are the alloy of iron and carbon that contains 2.1 to 4.3% C, along with other varying amounts of silicon and manganese. This varying carbon range makes them easily castable, asking them to call cast irons.
Question 9
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
View Answer
Answer: Option A
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.
Question 10
γ form of iron is?
A. Magnetic
B. Non magnetic
C. Occurs below 768oC
D. Occurs above 1410oC
View Answer
Answer: Option A
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.