MATERIAL SCIENCE MCQ SET 6
Q1. The hardness of steel can be increased by:
A) Annealing
B) Normalizing
C) Quenching
D) Softening
Answer: C) Quenching
Explanation: Rapid cooling forms martensite, a hard and brittle phase, increasing hardness.
Q2. Which metal has a hexagonal close-packed (HCP) structure?
A) Iron (at room temperature)
B) Copper
C) Zinc
D) Aluminum
Answer: C) Zinc
Explanation: Zinc crystallizes in HCP structure, limiting slip systems and reducing ductility.
Q3. The material most suitable for electrical insulation is:
A) Copper
B) Aluminum
C) Ceramic
D) Steel
Answer: C) Ceramic
Explanation: Ceramics are excellent insulators due to high resistivity and low free electrons.
Q4. Which of the following is a quaternary alloy?
A) Brass
B) Steel
C) Stainless steel
D) Inconel
Answer: D) Inconel
Explanation: Inconel contains nickel, chromium, iron, and other elements; hence, quaternary.
Q5. The main constituent of gray cast iron is:
A) Pearlite
B) Ferrite
C) Graphite
D) Cementite
Answer: C) Graphite
Explanation: Gray cast iron has flake graphite in a pearlitic or ferritic matrix, giving good damping properties.
Q6. Which test measures a materialโs resistance to indentation?
A) Tensile test
B) Hardness test
C) Impact test
D) Fatigue test
Answer: B) Hardness test
Explanation: Rockwell, Brinell, and Vickers tests measure hardness by indentation depth or size.
Q7. Which phase in steel is soft and ductile?
A) Ferrite
B) Cementite
C) Martensite
D) Bainite
Answer: A) Ferrite
Explanation: Ferrite (ฮฑ-Fe) is soft, ductile, and magnetic at room temperature.
Q8. Bainite offers:
A) Maximum hardness
B) Maximum toughness
C) Moderate strength and toughness
D) Only ductility
Answer: C) Moderate strength and toughness
Explanation: Bainite is formed at intermediate temperatures, balancing strength and toughness.
Q9. The process of adding carbon to steel at high temperature is called:
A) Nitriding
B) Carburization
C) Annealing
D) Tempering
Answer: B) Carburization
Explanation: Carburization increases surface carbon content to improve hardness and wear resistance.
Q10. The fracture of brittle materials occurs:
A) Slowly with plastic deformation
B) Suddenly without plastic deformation
C) Only under tension
D) Only under compression
Answer: B) Suddenly without plastic deformation
Explanation: Brittle fracture occurs almost instantaneously with minimal plastic deformation.
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