31. Match the scientist pairs listed in Group I with phenomena listed in Group II.
Group I
Group II
P. Hall-Patch
1. Dislocation reaction product
Q. Nabarro-Herring
2. Diffusional creep
R. Lomer-Cottrell
3. Dislocation source
S. Frank-Read Group
4. Grain boundary strengthening
| Group I | Group II |
| P. Hall-Patch | 1. Dislocation reaction product |
| Q. Nabarro-Herring | 2. Diffusional creep |
| R. Lomer-Cottrell | 3. Dislocation source |
| S. Frank-Read Group | 4. Grain boundary strengthening |
32. The diffusion couple shown below is made from two A-B alloys. The initial compositions of the two alloys are indicated in the diagram. The centreline is at x = 0. The couple is held at an elevated temperature for 40 hours. Diffusivity; D = 3 × 10-11 m-2 s-1. Assume the diffusion couple to be infinitely long.
Which of the parameters give the composition profile in the following form?
$$C\left( {x,t} \right) + {c_1} + {c_2}\,erf\left( {\frac{1}{{2\sqrt {Dt} }}} \right)$$
Which of the parameters give the composition profile in the following form?
$$C\left( {x,t} \right) + {c_1} + {c_2}\,erf\left( {\frac{1}{{2\sqrt {Dt} }}} \right)$$
33. In order to double its yield strength, the grain size of a steel of ASTM grain size number 2 should be changed to ASTM grain size number (neglect friction stress)
34. Ratio of tetrahedral to octahedral voids in FCC
35. The effective number of lattice points in the unit cell of end centered monoclinic lattice is
36. Which of the following phenomenon/phenomena is/are diffusion controlled?
37. Maraging steels derive their strength from the following mechanism:
38. Yield strength ofapolycrystalline metal with an average grain size, d, is proportional to
39. Under application of stress, when a straight dislocation (radius of curvature, r = ∞) tries to bow out around precipitates of spacing L, there is an instability during changing of curvature at
40. Which one of the following is an equilibrium defect?
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