MCQOPTIONS
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MCQOPTIONS
This section includes 14 Mcqs, each offering curated multiple-choice questions to sharpen your Phase Transformation knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Nucleation on dislocations may also be assisted by solute segregation which can raise the composition of the matrix to nearer that of the precipitate. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 2. |
In FCC crystals the a/2*[110] unit dislocations can dissociate to produce a ribbon of stacking fault. Which among the following is as an example of the same? |
| A. | a/2*[110]->a/6*[121] + a/6[211] |
| B. | a/2*[110]->a/6*[101] + a/6[201] |
| C. | a/2*[110]->a/6*[821] + a/6[911] |
| D. | a/2*[110]->a/6*[161] + a/6[221] |
| Answer» B. a/2*[110]->a/6*[101] + a/6[201] | |
| 3. |
A coherent nucleus with a negative misfit can reduce the critical volume free energy by forming a region of _________ |
| A. | Compressive strain |
| B. | Compressive stress |
| C. | Tensile strain |
| D. | Tensile stress |
| Answer» B. Compressive stress | |
| 4. |
At very small driving forces, when activation energy barriers for nucleation are high, the highest nucleation rates will be produced by grain corner nucleation. |
| A. | False |
| B. | True |
| Answer» C. | |
| 5. |
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 ( G*(hom) G*(het)/kT) to be 1) |
| A. | 0.5 |
| B. | 1.2 |
| C. | 0.25 |
| D. | 1.25 |
| Answer» B. 1.2 | |
| 6. |
What is special about the dark-field electron microscope micrograph? |
| A. | Precipitates can be imaged bright and matrix dark |
| B. | 360 degree rotation is possible |
| C. | High speed imaging is possible |
| D. | Anti roller scheme available |
| Answer» B. 360 degree rotation is possible | |
| 7. |
Excess vacancies are retained during the quench if the age hardening alloys are retained from______ |
| A. | Dark texture |
| B. | Room temperature |
| C. | Low temperature |
| D. | High temperature |
| Answer» E. | |
| 8. |
If the G* heterogeneous is given as 5kJ/mol and G* homogeneous is given as 10kJ/mol. Calculate the shape factor? |
| A. | 0.5 |
| B. | 1 |
| C. | 2 |
| D. | 2.5 |
| Answer» B. 1 | |
| 9. |
Calculate the shape factor if the angle tends to 90 degree? |
| A. | 0 |
| B. | 1 |
| C. | 2 |
| D. | 4 |
| Answer» C. 2 | |
| 10. |
The ability of the grain boundary to reduce the value of critical free energy G* depends on |
| A. | Cos |
| B. | Sin |
| C. | Tan |
| D. | Cot |
| Answer» B. Sin | |
| 11. |
If we ignore the effect of misfit strain energy, which among the following could minimize the interfacial free energy? |
| A. | Optimum embryo texture |
| B. | Optimum embryo shape |
| C. | Optimum embryo volume |
| D. | Optimum embryo length |
| Answer» C. Optimum embryo volume | |
| 12. |
Which among the following equation satisfies heterogeneous nucleation? |
| A. | Ghet = V*( Gv Gs) + A Gd |
| B. | Ghet = V*( Gv Gs) Gd |
| C. | Ghet = V*( Gv Gs) + A + Gd |
| D. | Ghet = V*( Gv Gs) + A |
| Answer» B. Ghet = V*( Gv Gs) Gd | |
| 13. |
If the creation of a nucleus results in the destruction of a defect this will result in the_______ |
| A. | Destruction of new nuclei |
| B. | Mass production of new nuclei |
| C. | Change of phase |
| D. | Reduction of activation energy barrier |
| Answer» E. | |
| 14. |
Nucleation in solids, as in liquids, in most cases is always __________ |
| A. | Homogeneous |
| B. | Heterogeneous |
| C. | Mixed |
| D. | Semi heterogeneous |
| Answer» C. Mixed | |