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. |
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. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 2. |
Driving force for precipitation (ΔGv) is the main factor in controlling_________ |
| A. | The energy barrier or critical free energy |
| B. | Size of the nuclei |
| C. | Surface energy |
| D. | Rate of fusion |
| Answer» B. Size of the nuclei | |
| 3. |
Which among the following curve represents the surface energy term? |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» B. 2 | |
| 4. |
Equilibrium phase is probably formed homogeneously at a few tens of degrees undercooling is at the precipitation of Ni3Al in many Ni-rich alloys. |
| A. | False |
| B. | True |
| Answer» C. | |
| 5. |
Which among the following can make the homogeneous reaction feasible? |
| A. | Contraction relationship |
| B. | Circuit orientation |
| C. | Orientation relationship |
| D. | It is not possible |
| Answer» D. It is not possible | |
| 6. |
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 ______ |
| A. | Vibrational frequency of atoms |
| B. | Radius of atoms |
| C. | Texture of the phase |
| D. | Nothing can be predicted |
| Answer» B. Radius of atoms | |
| 7. |
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) |
| A. | N (hom) = f*C |
| B. | N (hom) = f/C |
| C. | N (hom) = f+C |
| D. | N (hom) = f-C |
| Answer» B. N (hom) = f/C | |
| 8. |
In which among the following system does the equilibrium phase nucleate homogeneously? |
| A. | Cu-Co |
| B. | S-P |
| C. | Cu-Ag |
| D. | Au-Cu |
| Answer» B. S-P | |
| 9. |
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) |
| A. | ΔG/4πr2 |
| B. | ΔG/4πr3 |
| C. | ΔG/((4/3)*πr2) |
| D. | ΔG/4πr |
| Answer» B. ΔG/4πr3 | |
| 10. |
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) |
| A. | Cx |
| B. | Cx*exp (1) |
| C. | Cx*exp (-1) |
| D. | Nothing can be predicted |
| Answer» B. Cx*exp (1) | |
| 11. |
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? |
| A. | Creation of α/β interface |
| B. | Diffusion of α matrix |
| C. | Diffusion of β matrix |
| D. | Nothing can be predicted |
| Answer» B. Diffusion of α matrix | |
| 12. |
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? |
| A. | (16/7) γ3 |
| B. | (76/3) γ3 |
| C. | (16/3) γ3 |
| D. | (3/16) γ3 |
| Answer» D. (3/16) γ3 | |
| 13. |
What will happen to critical radius if the value of ΔGs, ΔGv becomes same? |
| A. | Tends to infinity |
| B. | Tends to 0 |
| C. | Unity |
| D. | No relation |
| Answer» B. Tends to 0 | |
| 14. |
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______ |
| A. | 0 |
| B. | VΔGs + VΔGv |
| C. | Aγ |
| D. | Cannot be determined |
| Answer» D. Cannot be determined | |