Mechanical Engineering MCQs
Types Sintering
1. _________ refers to those processes where solid and liquid coexist during the entire or part of the sintering process.
A. Spark plasma sintering
B. SHS
C. Activated sintering
D Liquid phase sintering
Answer: D
2. Doping of Ni in tungsten compacts is an example of _________
A. Activated sintering
B. Reaction sintering
C. Microwave sintering
D Gas plasma sintering
Answer: A
3. Which of the following characteristic the ‘doping’ additive should not possess?
A. Segregate at the grain boundary
B. Formation of low melting point phase
C. High atomic weight
D High solubility
Answer: C
4. The presence of nickel at grain boundaries greatly increases the grain boundary lattice-diffusion of tungsten.
A. True
B. False
Answer: B
5. _______ takes place when two or more components chemically react during the sintering process to form the final product.
A. Rate controlled sintering
B. Reaction sintering
C. Microwave sintering
D Spark plasma sintering
Answer: B
6. SiN is prepared by _______
A. Reaction sintering
B. Hot forging
C. Solid-state sintering
D Liquid phase sintering
Answer: A
7. _________ has the advantage of producing a finer grain size compared to pressureless sintering.
A. Solid-state sintering
B. Microwave sintering
C. Liquid phase sintering
D Reaction sintering
Answer: B
8. _______ is an exothermic combustion process that uses the heat generated during a reaction to sinter the material.
A. SHS
B. Gas plasma sintering
C. Spark plasma sintering
D Rate controlled sintering
Answer: A
9. _______ is a process similar to the hot uniaxial pressing.
A. Solid-state sintering
B. SHS
C. SPS
D Activated sintering
Answer: C
10. The _______ defines sintering as, “the thermal treatment of a powder or compact at a temperature below the melting point of the main constituent, for the purpose of increasing its strength by bonding together of the particles”.
A. ASME
B. ASTM
C. ISO
D BIS
Answer: C
11. ________ transforms compacted mechanical bonds between powder particles into metallurgical bonds.
A. Sintering
B. SHP
C. Mechanical alloying
D Metal Injection Molding
Answer: A
13. In _________, the densification is a result of atomic diffusion in solid-state.
A. Reaction sintering
B. Solid-state sintering
C. Activated sintering
D Liquid phase sintering
Answer: B
Sintering Theory – 1
1. Which of the following changes do not occur on during recrystallization?
A. Pore shrinkage
B. Phase changes
C. Grain shrinkage
D. Precipitation
Answer: C
2. _______ requires mass transport.
A. Pore expansion
B. Grain shrinkage
C. Densification
D. Adhesion
Answer: C
3. The driving force for sintering is reduction in ________
A. Internal energy
B. Surface tension
C. Surface energy
D. Entropy
Answer: C
4. The initial free energy of the compact before sintering must be _______
A. Positive
B. Negative
C. Zero
D. Infinite
Answer: B
5. To achieve densification during sintering without grain growth, the γSS must be _____, while the γSV must be _____
A. Zero, maximized
B. Maximized, zero
C. Zero, minimized
D. Maximized, minimized
Answer: B
6. It is desirable that sintering stops when ______
A. dASVdASSis close to zero
B. dASSdASV is close to zero
C. γSS >> γSV
D. −dASVdASSis close to zero
Answer: D
7. Sintering can be considered as an irreversible thermodynamic process.
A. True
B. False
Answer: A
8. Sintering involves _____ types of system.
A. Unary
B. Binary
C. Single component andmulticomponent
D. Ternary
Answer: C
9. _______ is the major material transport mechanism in sintering of the single component system.
A. Inter-diffusion
B. Self-diffusion
C. Lattice-diffusion
D. Volume-diffusion
Answer: B
10. Which of the following are the stages of sintering, according to Sauerwald theory?
A. Adhesion, recrystallization
B. Adhesion, crystallization
C. Adhesion
D. Adhesion, bonding
Answer: A
Sintering Theory – 2
1. The ________ gradient is high for small neck size leading to faster sintering.
A. Curvature
B. Linear
C. Volume
D. Velocity
Answer: A
2. The driving force for the various stages of solid-state sintering are ________ and ________
A. Lattice diffusion and capillary force
B. Surface tension forces and diffusional flow
C. Surface tension forces and plastic flow
D. Lattice diffusion and surface tension force
Answer: B
3. ________ is the mechanism by which bulk transportation can take place in solid-state sintering.
A. Surface diffusion
B. Plastic flow
C. Adhesion
D. Evaporation-condensation
Answer: B
4. Which of the following is not a mechanism of by which surface transportation occur during solid-state sintering?
A. Plastic flow
B. Volume diffusion
C. Viscous flow
D. Surface diffusion
View Answer
Answer: D
5. Solid-state sintering can be broadly divided into _____ stages.
A. Adhesion, and Densification
B. Adhesion, Densification, and spheroidization of isolated pores
C. Adhesion, and grain growth
D. Initial bonding, and spheroidization of isolated pores
Answer: B
6. In final stage of solid-state sintering, _____ become isolated and are no longer _______
A. Grains, connected
B. Grains, interconnected
C. Pores, open
D. Pores, interconnected
Answer: D
7. The first stage of solid-state sintering, includes _______ of vacancies and ________ between surface regions with different radii of curvature.
A. Surface diffusion, volume diffusion
B. Volume diffusion, surface diffusion
C. Lattice diffusion, surface diffusion
D. Plastic flow, surface diffusion
Answer: B
8. In which stage of solid-state sintering the pores are interconnected and pore shape is irregular?
A. 1st
B. 2nd
C. 3rd
D. 4th
Answer: A
9. In the second stage of sintering, with sufficient neck growth, the pore channels become more _______ in nature.
A. Spherical
B. Cylindrical
C. Cubical
D. Linear
Answer: B
Sintering Mechanism – 1
1. The equilibrium vapor pressure over the neck _____ particle surface.
A. < B. >
C. =
D. >>
Answer: A
2. Diffusion occurs as a result of _______ gradient.
A. Velocity
B. Vacancy concentration
C. Pressure
D. Momentum
Answer: B
3. Vacancy concentration causes _______
A. The outflow of vacancies from the curved surface towards the flat region
B. The outflow of vacancies from the flat surface towards the curved region
C. The outflow of atoms from the curved surface towards the flat region
D. The influx of vacancies from the curved surface towards the flat region
Answer: A
4. The vacancy concentration is given by Dvac= ______
A. D.C0
B. D.C
C. d.C
D. D.c
Answer: A
5. What is the empirical relationship for the rate of neck growth when a sphere is in contact with a flat surface?
A. Rate of neck growth ∝ t16
B. Rate of neck growth ∝ t17
C. Rate of neck growth ∝ t27
D. Rate of neck growth ∝ t18
Answer: B
7. Which of the following are the main types of material transport mechanisms proposed to be operating during sintering?
A. Evaporation
B. Dislocation movement
C. Evaporation-condensation, viscous flow, plastic flow and diffusion
D. Viscous flow, metal flow
Answer: C
8. _______ is the ‘liquid-like’ movement of individual atoms under stress while _______ is the slip of entire planes of atoms.
A. Plastic flow, viscous flow
B. Volume diffusion, plastic flow
C. Viscous flow, volume diffusion
D. Viscous flow, plastic flow
Answer: D
9. ________ mechanism operates in a system having materials with a high vapor pressure at sintering temperature.
A. Viscous flow
B. Volume diffusion
C. Evaporation and condensation
D. Plastic flow
Answer: C
10. The driving force for evaporation-condensation mechanism is given by ________
A. μ-μ0=(γΩ)/r1=RT lnp0p
B. μ-μ0=(-γΩ)/r1=RT lnpp0
C. μ0-μ=(-γΩ)/r1=RT lnpp0
D. μ-μ0=(γΩ)/r1=RT lnpp0
Answer: B
11. The mass transport during evaporation-condensation mechanism occurs from _______ particle surface to the ______ necks.
A. Concave, convex
B. Convex, bi-concave
C. Convex, concave
D. Bi-convex, concave
Answer: C
Sintering Mechanism – 2
1. Which of the following mechanism does not lead to shrinkage?
A. Viscous flow
B. Surface diffusion
C. Volume diffusion
D. Grain boundary diffusion
Answer: B
2. ________ mechanism alters the shape of the neck and particle surface.
A. Viscous flow
B. Volume diffusion
C. Evaporation-condensation
D. Plastic flow
Answer: C
3. According to ______, there are six stages of sintering.
A. Schroter
B. Nabarro and Herring
C. Kuczynsky
D. Hutteg
Answer: D
4. Which of the following transport mechanisms can occur for two spheres in contact with one another during sintering?
A. Evaporation-condensation, surface diffusion and volume diffusion
B. Evaporation-condensation, surface diffusion, volume diffusion, volume diffusion of vacancies, and grain boundary diffusion
C. Surface diffusion
D. Volume diffusion
Answer: B
1. Coble developed rate equations for three stage sintering assuming the compact to be made of packed spheres and in the final stage form interlocking ___________
A. Tetrakaioctahedrons
B. Tetrakaidecahedrons
C. Tetracontagons
D. Tetrakaitetrahedrons
Answer: B
2. Entrapment of gas within the pores is an important reason for not achieving theoretical density in practice during sintering.
A. True
B. False
Answer: A
3. Bulk flow of material by movement of dislocations is a possible mechanism for densification during sintering only if the two conditions are met.
A. True
B. False
Answer: A
4. Nabarro and Herring supported ________ as the dominant mechanism in sintering.
A. Evaporation-condensation
B. Viscous flow
C. Diffusion
D. Recrystallization
Answer: C
5. ___________ are structural arrangement of dislocations and are not perfect sinks.
A. Pores
B. Grain boundaries
C. Vacancies
D. Necks
Answer: B
6. Which of the following mechanisms operate during sintering, according to Bal’shin theory?
A. Particle re-arrangement, particle shape change, and grain shrinkage
B. Particle shape change, particle size change, and grain growth
C. Particle re-arrangement, particle shape change, and grain growth
D. Particle re-arrangement and grain growth
Answer: C
Structure and Property Changes during Sintering
1. Densification cannot be treated as equal to the amount of porosity removed.
A. True
B. False
Answer: A
2. Sintering results in ________
A. Change in structure of compact
B. Structural change, recrystallization, and grain shrinkage
C. Structural change, reduction of surface oxides, and grain growth
D. Pore growth
Answer: C
Sintering of Multicomponent System – 1
1. _________ is an example of multicomponent sintering.
A. Liquid phase sintering
B. Solid-state sintering
C. Microwave sintering
D. Reaction sintering
Answer: A
2. Which of the is the must consideration for liquid phase sintering to occur?
A. Incomplete wetting of liquid in solid
B. Appreciable insolubility of solid in liquid
C. Presence of a limited amount of liquid phase
D. Appreciable solubility of solid in liquid
Answer: D
3. ______ is the form of liquid phase sintering where liquid formed is temporary in nature.
A. Transient liquid phase sintering
B. Persistent liquid phase sintering
C. Transistor liquid phase sintering
D. Progressive liquid phase sintering
Answer: A
4. Which of the following is the correct sequence for liquid phase sintering?
A. Liquid flow stage → Precipitation stage → Solid-state sintering stage
B. Liquid flow stage → Condensation stage → Liquid-state sintering stage
C. Liquid flow stage → Solution and reprecipitation stage → Liquid-state sintering stage
D. Liquid flow stage → Solution and reprecipitation stage → Solid-state sintering stage
Answer: D
5. In sintering of multicomponent systems, the material transport mechanisms involve ______
A. Self-diffusion
B. Self-diffusion and inter-diffusion
C. Inter-diffusion
Answer: B
6. Enhanced volume diffusion is the reason for adding Ni for activated sintering of refractory metals.
A. True
B. False
Answer: B
7. The __________ is the motion of the interface that occurs due to the difference in diffusion rates of the metal atoms.
A. Darkens effect
B. Schroter effect
C. Kirkendall effect
D. Harmer effect
Answer: C
8. ______ dihedral angle, will hinder further densification.
A. Negative
B. Zero
C. Positive
D. Infinite
Answer: C
9. In liquid phase sintering, ______ stresses are developed at the contact point of two particles when the dihedral angle is zero.
A. Bending
B. Shear
C. Tensile
D. Compressive
Answer: D
10. ______ amount of liquid phase must be present to penetrate the adjoining grains.
A. Minimum
B. Sufficient
C. Maximum
D. Unlimited
Answer: B
11. Liquid phase sintering is advantageous over solid phase sintering due to ______
A. Temperature
B. Microstructure
C. Kinetics
D. Economy
Answer: C
12. The greater the ______ more will be the driving force for the liquid flow stage in the liquid phase sintering.
A. Wetting
B. Temperature
C. Pressure
D. Diffusion
Answer: A
13. For liquid phase to sinter successfully, the contact angle should be _______
A. more than 90°
B. less than 90°
C. equal to 90°
D. equal to 0°
Answer: B
14. Initial particle size must be small for liquid phase sintering.
A. True
B. False
Answer: A
15. Which of following is the correct set of material variables in sintering?
A. Particle structure and sintering atmosphere
B. Particle composition, particle shape, green density and sintering temperature
C. Green density and sintering time
D. Green density and particle size
Answer: D
16. ________ particle size leads to increased sintering.
A. Finer
B. Coarse
C. Medium
D. Ultra-coarse
Answer: A
17. A _______ in green density signifies a greater driving force for sintering.
A. Maximum
B. Sufficient
C. Decrease
D. Increase
Answer: C
18. Heterogenous nature of powders improve sintering kinetics.
A. True
B. False
Answer: A
19. ________ sphericity and ________ macro or micro-surface roughness promote sintering.
A. Decreasing, decreasing
B. Increasing, decreasing
C. Decreasing, increasing
D. Increasing, increasing
Answer: C
20. The degree of sintering _______ with increasing time, though the effect is small in comparison to the effect of temperature.
A. Unaffected
B. Constant
C. Decreases
D. Increases
Answer: D
Sintering Practice and Sintering Furnace – 1
1. ________ type furnaces require large volumes of protective gases.
A. Ram-up
B. Roller hearth
C. Mesh-belt
D. Pulley-lift
Answer: C
2. By measuring _________ of effluent gas from the furnace continuously, the completeness of purge can be identified.
A. Dew point
B. Specific gravity
C. Carbon potential
D. Gas content
Answer: B
3. In _______, the analysis takes place in two phases, the absorption phase, and the burning phase.
A. Ortab type analyzer
B. Orsat type analyzer
C. Infrared type analyzer
D. Orson type analyzer
Answer: B
4. ________ works on the principle that each constituent of the sintering atmosphere absorbs infrared energy at a characteristic wavelength.
A. Infrared analyzer
B. Orsat type analyzer
C. Energy analyzer
D. Wave analyzer
Answer: A
5. The compacts entering into the burn-off zone must be heated ________
A. Slowly
B. Moderately
C. Rapidly
D. Any desired rate
Answer: A
6. Incomplete burnout leads to ________ and discoloration of the components.
A. Pungent smell
B. Reduction
C. Cracking
D. Sooting
Answer: D
7. The sintering zone must be ________ in length in relation to the burn-off zone.
A. Shorter
B. Longer
C. Moderate
D. Equal
Answer: B
8. The cooling zone of a sintering furnace is made up of _______
A. A short-insulated cooling zone
B. A short conductive cooling zone and longer oil jacketed cooling zone
C. A longer water-jacketed cooling zone
D. A short-insulated cooling zone and longer water-jacketed cooling zone
Answer: D
9. Which of the following condition is necessary for obtaining consistent and satisfactory sintered components?
A. More labor cost
B. Long sintering time
C. High power consumption
D. Short sintering time
Answer: D
10. On the basis of which of the following factors a sintering furnace is selected?
A. Cost
B. Furnace lining
C. Working temperature range
D. Shape
Answer: C
11. Which of the following are the essential parts of a sintering furnace?
A. Burn-on zone, sintering zone, and cooling zone
B. Burn-off zone, sintering zone, and cooling zone
C. Preheat zone and sintering zone
D. Sintering zone and cooling zone
Answer: B
Sintering – Infiltration
1. A _____ wetting angle promotes infiltration.
a) low
b) 0°
c) 90°
d) large
Answer: A
2. The infiltration process is used to prepare ____ kinds of material.
a) Single phase materials
b) Duplex materials
c) Single phase, and duplex materials
d) Multicomponent materials
Answer: C
4. Erosion of the contact surfaces of the skeleton metal can be reduced by ______ method.
a) Bridge method
b) Oil method
c) Flyover method
d) Compensation method
Answer: A
5. Why alloy infiltrant is used for the production of copper-infiltrated ferrous base materials?
a) Cost-saving
b) Reduce erosion of contact surfaces of the skeleton
c) Material saving
d) Variety production
Answer: B
6. Why infiltrated pump cylinder blocks are popular in use?
a) Mechanical strength
b) Resistance to thermal stress
c) Pressure- tightness
d) Light-weight
Answer: C
7. ______ process involves preparing a porous metallic body and filing its pores with a molten metal having a lower melting point.
a) Liquid phase sintering
b) Infiltration
c) Densification
d) Alloying
Answer: B
8. A continuous network of infiltrant metal is a must.
a) True
b) False
Answer: A
9. How many stages occur in the process of infiltration?
a) 5
b) 2
c) 3
d) 4
Answer: B
10. Which of the following is not a characteristic of infiltrant?
a) Melting point lower than the skeleton metal
b) High surface tension
c) Good or perfect wetting
d) Must not alloy or react with the skeleton metal
Answer: B
11. For infiltration, the porosity in the skeleton should be ________
a) Closed
b) Interconnected
c) Open
d) Intermittent
Answer: B
12. __________ are among the most important P/M parts produced by infiltration.
a) Electrical contacts
b) Cermet
c) Sintered carbides
d) Porous P/M parts
Answer: A
13. Which of the following changes does not improve the process of infiltration?
a) Lowering the interfacial tension between skeleton and infiltrant
b) Removing dissolved or adsorbed elements in the skeleton
c) Increasing surface energy of the infiltrant
d) Increasing the interfacial tension between skeleton and infiltrant
Answer: D
