CMS Industrial Materials & Metallurgy 2 — Questions and Answers
Question 1: Which heat treatment process involves heating steel above its critical temperature and then cooling it slowly in the furnace to reduce hardness and improve machinability?
- Normalizing
- Annealing (Correct answer)
- Quenching
- Tempering
Correct answer: Annealing
Annealing involves heating steel above its critical temperature and then furnace-cooling it slowly, which softens the metal and improves machinability.
Question 2: What is the primary purpose of adding chromium to stainless steel?
- Increase electrical conductivity
- Provide corrosion resistance through passive oxide layer (Correct answer)
- Reduce the melting point
- Improve weldability
Correct answer: Provide corrosion resistance through passive oxide layer
Chromium (minimum 10.5%) reacts with oxygen to form a thin, stable Cr₂O₃ passive layer on the steel surface that prevents corrosion.
Question 3: A manufacturer needs a material with high strength-to-weight ratio for aerospace components. Which material family is most appropriate?
- Cast iron
- Carbon steel
- Titanium alloys (Correct answer)
- Brass
Correct answer: Titanium alloys
Titanium alloys offer exceptional strength-to-weight ratios and corrosion resistance, making them the preferred choice for aerospace structural components.
Question 4: What does the Rockwell hardness test measure differently from the Brinell hardness test?
- It measures the diameter of an indentation
- It measures the depth of penetration under a fixed load (Correct answer)
- It measures surface reflectivity
- It measures tensile strength directly
Correct answer: It measures the depth of penetration under a fixed load
Rockwell hardness measures the depth of indentation under a prescribed load, while Brinell measures the diameter of the indentation left by a hardened ball.
Question 5: Which phase diagram feature indicates the temperature at which a single-phase liquid transforms directly into two solid phases simultaneously?
- Liquidus line
- Solidus line
- Eutectic point (Correct answer)
- Peritectic point
Correct answer: Eutectic point
The eutectic point is the specific temperature and composition at which a liquid transforms simultaneously into two distinct solid phases.
Question 6: What manufacturing defect occurs when dissolved gases are trapped in molten metal during solidification, creating voids in the casting?
- Hot tears
- Porosity (Correct answer)
- Cold shuts
- Shrinkage cavities
Correct answer: Porosity
Porosity is caused by dissolved gases (typically hydrogen) coming out of solution during solidification and becoming trapped as small voids in the casting.
Question 7: Which type of composite material uses carbon fibers embedded in an epoxy resin matrix and is commonly used in high-performance structural applications?
- Metal matrix composite (MMC)
- Ceramic matrix composite (CMC)
- Carbon fiber reinforced polymer (CFRP) (Correct answer)
- Glass fiber reinforced polymer (GFRP)
Correct answer: Carbon fiber reinforced polymer (CFRP)
Carbon fiber reinforced polymer (CFRP) combines high-strength carbon fibers in an epoxy matrix to produce lightweight, high-stiffness structural components.
CMS Industrial Materials & Metallurgy 2
Which heat treatment process involves heating steel above its critical temperature and then cooling it slowly in the furnace to reduce hardness and improve machinability?