This set of Phase Transformation Interview Questions and Answers for freshers focuses on “Diffusion in Multiphase Binary Systems”.
1. Which of the following is an example of Diffusion in multi-phase binary system?
a) Alcohol in water
b) Aldehyde in water
c) Ketone in water
d) Galvanized iron and hot-dipped tin plate
View Answer
Explanation: In case of a hot dipped tin plate and galvanized iron the welding takes place between the two metals that are not completely miscible in each other and in this diffusion couples the multi-phase diffusion arises.
2. Non equilibrium diffusion couples, a situation often encountered at ________
a) High temperature
b) Low temperature
c) When nucleation is perfect
d) Annealing time is too long
View Answer
Explanation: This is situation often encountered when the annealing time is short, or when the nucleation problems exist or when the interface energy plays a significant role and it can also arise when the temperature is low.
3. If the diffusion couple technique is not used in a proper way which of the following error is most likely to occur?
a) The necessity to use the decremented couples
b) Small roles played by impurities
c) Steep concentration gradient may occur in the growing phases
d) No errors are likely to occur
View Answer
Explanation: If the diffusion couple technique is not used in a proper way then steep concentration gradient may occur in the growing phases. Unleβ the role played by the impurities are large it doesn’t create an error in the system. The necessity to use the incremental couples because of the problem of missing plane.
4. Which among the following can give an extra information on layer growth mechanism and concentration limit of various phases?
a) Edges and free surface of diffusion couple
b) Positions of dislocation
c) Composition ratio
d) Shape of the interface
View Answer
Explanation: Generally, the edges and free surface of diffusion couple can give an extra information on layer growth mechanism and concentration limit of various phases. Often the surface diffusion or evaporation/condensation give rise to the formation of larger number of phases rich in substrate material compared to regular diffusion zone because of impeded supply of diffusion material.
5. Under some circumstances the interface migration is said to be interface controlled.
a) True
b) False
View Answer
Explanation: Under some circumstances the interface migration is said to be interface controlled. In some cases the interface migration can be slow and there are virtually no concentration gradient in the two phases. These are some extreme cases.
6. The flux of atoms to the interface balance the________
a) Rate of accumulation due to the boundary migration
b) Mass of the system
c) Volume of the system
d) Stability of the grain boundary
View Answer
Explanation: Here the rate of transfer across the interface can be balanced along with the rate of accumulation due to migration and the rate of diffusion away into the other phase, this is done by the flux of atoms to the interface.
7. Accurate microbe analysis near the interfaces are very difficult if the fluorescent effect affects the concentration measurements at distance as large as 40*10-6m from the interface.
a) True
b) False
View Answer
Explanation: Accurate microbe analysis near the interfaces are very difficult if the fluorescent effect affects the concentration measurements at distance as large as 40*10-6m from the interface. In binary couples, usually one of the elements does not affect from the fluorescent effect and one could measure the concentration of that element by the microbe analysis to describe the penetration plot.
8. The direction of the longest crystallographic axis is invariably oriented __________
a) Parallel to diffusion direction
b) Perpendicular to interface
c) Perpendicular to diffusion direction
d) Cannot be predicted
View Answer
Explanation: The direction of the longest crystallographic axis is invariably oriented perpendicular to the diffusion direction, which is parallel to the interface. Very often the crystals of phases in the diffusion-grown layers have a preferred orientation in the growth (Diffusion) direction.
9. If a single crystalline layer of γ is growing between single crystalline substrate α and β, one might expect a completely_____
a) Straight α/γ and γ/β interfaces
b) Curved α/γ and γ/β interfaces
c) Straight γ/α and γ/β interfaces
d) Curved γ/α and γ/β interfaces
View Answer
Explanation: If a single crystalline layer of γ is growing between single crystalline substrate α and β, one might expect a completely straight α/γ and γ/β interfaces, provided that no orientation related effect occur which might cause a faceted interface. In a polycrystalline layer grown between polycrystalline end members, the interfaces are not completely straight.
10. The shortest repeat-distance is aligned parallel to the direction of diffusion (fiber texture). This statement is known as____
a) Perkin rule
b) Thumb rule
c) Henrys rule
d) Marks direction principle
View Answer
Explanation: According to the rule of Thumb the shortest repeat-distance is aligned parallel to the direction of diffusion (fiber texture). These textures are most pronounced at the growth front of the reaction layer. In the oldest part of the layer sometimes change in texture are found due to recrystallization.
Sanfoundry Global Education & Learning Series – Phase Transformation.
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