Phase Transformation MCQ

Test your knowledge with important Phase Transformation MCQ and their applications. These MCQs are beneficial for competitive exams too. Explore 30+ more Phase Transformation MCQs on Bissoy. Bissoy App

• Nucleation on dislocations may also be assisted by solute segregation which can raise the composition of the matrix to nearer that of the precipitate.
  ক

  True

  খ

  False
• Which among the following curve represent the grain boundary?
  ক

  1

  খ

  2

  গ

  3

  ঘ

  Cannot be predicted
• In FCC crystals the a/2* unit dislocations can dissociate to produce a ribbon of stacking fault. Which among the following is as an example of the same? ->a/6* + a/6 b) a/2*->a/6* + a/6 c) a/2*->a/6* + a/6 d) a/2*->a/6* + a/6
  ক

  unit dislocations can dissociate to produce a ribbon of stacking fault. Which among the following is as an example of the same? ] a/2*->a/6* + a/6

  খ

  110

  গ

  110

  ঘ

  110
• A coherent nucleus with a negative misfit can reduce the critical volume free energy by forming a region of _________
  ক

  Compressive strain

  খ

  Compressive stress

  গ

  Tensile strain

  ঘ

  Tensile stress
• At very small driving forces, when activation energy barriers for nucleation are high, the highest nucleation rates will be produced by grain corner nucleation.
  ক

  False

  খ

  True
• The relative magnitudes of the heterogeneous and homogeneous volume nucleation rate is given as 0.5. Calculate the factor C/C1 (the number of atoms on heterogeneous sites relative to the number within the matrix)? (Consider exp (ΔG*(hom) – ΔG*(het)/kT) to be 1)
  ক

  0.5

  খ

  1.2

  গ

  0.25

  ঘ

  1.25
• What is special about the dark-field electron microscope micrograph?
  ক

  Precipitates can be imaged bright and matrix dark

  খ

  360 degree rotation is possible

  গ

  High speed imaging is possible

  ঘ

  Anti roller scheme available
• Excess vacancies are retained during the quench if the age hardening alloys are retained from______
  ক

  Dark texture

  খ

  Room temperature

  গ

  Low temperature

  ঘ

  High temperature
• If the ΔG* heterogeneous is given as 5kJ/mol and ΔG* homogeneous is given as 10kJ/mol. Calculate the shape factor?
  ক

  0.5

  খ

  1

  গ

  2

  ঘ

  2.5
• Calculate the shape factor if the angle tends to 90 degree?
  ক

  0

  খ

  1

  গ

  2

  ঘ

  4
• The ability of the grain boundary to reduce the value of critical free energy ΔG* depends on
  ক

  CosΦ

  খ

  SinΦ

  গ

  TanΦ

  ঘ

  CotΦ
• If we ignore the effect of misfit strain energy, which among the following could minimize the interfacial free energy?
  ক

  Optimum embryo texture

  খ

  Optimum embryo shape

  গ

  Optimum embryo volume

  ঘ

  Optimum embryo length
• Which among the following equation satisfies heterogeneous nucleation?
  ক

  ΔGhet = – V*(ΔGv – ΔGs) + Aγ – ΔGd

  খ

  ΔGhet = – V*(ΔGv – ΔGs) – ΔGd

  গ

  ΔGhet = – V*(ΔGv – ΔGs) + Aγ + ΔGd

  ঘ

  ΔGhet = – V*(ΔGv – ΔGs) + Aγ
• If the creation of a nucleus results in the destruction of a defect this will result in the_______
  ক

  Destruction of new nuclei

  খ

  Mass production of new nuclei

  গ

  Change of phase

  ঘ

  Reduction of activation energy barrier
• Nucleation in solids, as in liquids, in most cases is always __________
  ক

  Homogeneous

  খ

  Heterogeneous

  গ

  Mixed

  ঘ

  Semi heterogeneous
• In most systems the α and β phases have such different crystal structures that it is impossible to form coherent low-energy interfaces and homogeneous nucleation of the equilibrium β phase is then impossible.
  ক

  True

  খ

  False
• Driving force for precipitation (ΔGv) is the main factor in controlling_________
  ক

  The energy barrier or critical free energy

  খ

  Size of the nuclei

  গ

  Surface energy

  ঘ

  Rate of fusion
• Equilibrium phase is probably formed homogeneously at a few tens of degrees undercooling is at the precipitation of Ni3Al in many Ni-rich alloys.
  ক

  False

  খ

  True
• Which among the following can make the homogeneous reaction feasible?
  ক

  Contraction relationship

  খ

  Circuit orientation

  গ

  Orientation relationship

  ঘ

  It is not possible
• If each nucleus can be made supercritical at a rate of f per second the homogeneous nucleation rate is given as f*C (Assume C to be the concentration of critical-sized nuclei). The value of f depends on ______
  ক

  Vibrational frequency of atoms

  খ

  Radius of atoms

  গ

  Texture of the phase

  ঘ

  Nothing can be predicted
• If each nucleus can be made supercritical at a rate of f per second the homogeneous nucleation rate will be given by________ (Assume C to be the concentration of critical-sized nuclei)
  ক

  N (hom) = f*C

  খ

  N (hom) = f/C

  গ

  N (hom) = f+C

  ঘ

  N (hom) = f-C
• In which among the following system does the equilibrium phase nucleate homogeneously?
  ক

  Cu-Co

  খ

  S-P

  গ

  Cu-Ag

  ঘ

  Au-Cu
• If we ignore the variation of γ with interface orientation and assume the nucleus is spherical with a radius of curvature r, determine the value of γ if the value of (ΔGs-ΔGv) tends to zero? (ΔG represents the total energy)
  ক

  ΔG/4πr2

  খ

  ΔG/4πr3

  গ

  ΔG/((4/3)*πr2)

  ঘ

  ΔG/4πr
• Calculate the concentration of critical sized nuclei if the critical free energy tends to 0? (Assume the number of atoms per unit volume in the phase is given as Cx)
  ক

  Cx

  খ

  Cx*exp (1)

  গ

  Cx*exp (-1)

  ঘ

  Nothing can be predicted
• Consider the precipitation of B-rich β from a supersaturated A-rich α solid solution. Which among the following will lead to the creation of activation energy barrier?
  ক

  Creation of α/β interface

  খ

  Diffusion of α matrix

  গ

  Diffusion of β matrix

  ঘ

  Nothing can be predicted
• Calculate the value of critical free energy if the value of (ΔGs (misfit strain)-ΔGv) is given as 22/7? (γ represents the surface free energy?
  ক

  (16/7) γ3

  খ

  (76/3) γ3

  গ

  (16/3) γ3

  ঘ

  (3/16) γ3
• What will happen to critical radius if the value of ΔGs, ΔGv becomes same?
  ক

  Tends to infinity

  খ

  Tends to 0

  গ

  Unity

  ঘ

  No relation
• If values of the misfit energy term and reduction of volume free energy are the same then the total free energy during a homogeneous transformation is given as______
  ক

  0

  খ

  VΔGs + VΔGv

  গ

  Aγ

  ঘ

  Cannot be determined
• For both coherent and incoherent inclusion the misfit strain energy is proportional to____
  ক

  Shape of the inclusion

  খ

  Mass of the inclusion

  গ

  Density of the inclusion

  ঘ

  Volume of the inclusion
• Which among the following is not an example of permanent mold casting?
  ক

  Gravity

  খ

  Slush

  গ

  Vacuum

  ঘ

  Sand casting