ME Processing and Manufacturing 2 — Questions and Answers
Question 1: Chemical vapor deposition (CVD) is used in materials processing to:
- Remove material by chemical etching
- Deposit thin solid films from gaseous precursors onto a substrate (Correct answer)
- Join metals using a filler material
- Electroplate thick metal coatings
Correct answer: Deposit thin solid films from gaseous precursors onto a substrate
CVD involves chemical reactions of gaseous precursors at or near a heated substrate surface, depositing a solid thin film with excellent thickness uniformity.
Question 2: The main purpose of a Sendzimir (Z-mill) rolling configuration is to:
- Increase rolling speed for thick plates
- Allow rolling of hard, thin strips using small-diameter work rolls backed by many support rolls (Correct answer)
- Apply heat to the strip during rolling
- Reduce friction between rolls and material
Correct answer: Allow rolling of hard, thin strips using small-diameter work rolls backed by many support rolls
Z-mills use a cluster of backup rolls to support small-diameter work rolls, enabling rolling of hard alloys (stainless steel, titanium) into thin strip with high rolling forces.
Question 3: Forging produces parts with superior mechanical properties compared to casting primarily because:
- It eliminates all porosity
- It refines grain structure and aligns grain flow with part geometry (Correct answer)
- It uses lower temperatures
- It allows more complex shapes
Correct answer: It refines grain structure and aligns grain flow with part geometry
Forging aligns metal grains along the part geometry (grain flow), refines grain size, and eliminates casting defects, resulting in superior strength, toughness, and fatigue resistance.
Question 4: In welding metallurgy, the heat-affected zone (HAZ) is the region:
- Where the base metal melted and resolidified
- Adjacent to the weld that was not melted but experienced microstructural changes due to heat (Correct answer)
- Where filler metal was deposited
- Unaffected by the welding process
Correct answer: Adjacent to the weld that was not melted but experienced microstructural changes due to heat
The HAZ is the base metal region that did not melt but reached temperatures high enough to alter its microstructure, often resulting in grain growth or property changes.
Question 5: Physical vapor deposition (PVD) techniques such as sputtering differ from CVD primarily in that PVD:
- Requires temperatures above 1000 degrees C
- Deposits material from a solid or liquid source without chemical reactions in the vapor phase (Correct answer)
- Cannot produce metallic coatings
- Uses liquid precursors
Correct answer: Deposits material from a solid or liquid source without chemical reactions in the vapor phase
PVD physically converts a solid or liquid source material into vapor by sputtering or evaporation and deposits it on a substrate without gas-phase chemical reactions.
Question 6: A key challenge unique to additive manufacturing (AM) metal parts produced by selective laser melting (SLM) is:
- Parts have too low density
- High residual stresses and anisotropic microstructure from rapid solidification (Correct answer)
- Parts cannot be heat treated after printing
- Impossible to use titanium alloys in AM
Correct answer: High residual stresses and anisotropic microstructure from rapid solidification
Rapid, directional solidification in SLM creates columnar grain structures and high residual stresses that require post-processing such as stress relief annealing or HIP to achieve isotropic properties.
ME Processing and Manufacturing 2
Chemical vapor deposition (CVD) is used in materials processing to: