51. A number of solid state phase transformations follow a sigmoidal pattern. In these eases, at any time the fraction transformed can be expressed as
52. From an alloy, two specimens are machined and tested separately under tension and compression. The engineering stress-strain curves as well as the true stress-true strain curves for tension and compression are plotted in the same diagram. Identify the correct statements:
P. The engineering stress-strain curves in tension and compression are identical.
Q. The true stress-true strain curve in compression is lower than the true stresstrue strain curve in tension due to Bauschinger effect.
R. The true stress-true strain curve in tension is above the corresponding engineering stress-strain, curve.
S. The true stress-true strain curve in tension and compression are identical.
P. The engineering stress-strain curves in tension and compression are identical.
Q. The true stress-true strain curve in compression is lower than the true stresstrue strain curve in tension due to Bauschinger effect.
R. The true stress-true strain curve in tension is above the corresponding engineering stress-strain, curve.
S. The true stress-true strain curve in tension and compression are identical.
53. Which one of the following is a ferrite stabiliser in steels?
54. In Cu-Al phase diagram, the solubility of Al in Cu at room temperature is about 10% and that of Cu in Al is less than 1%. The Hume-Rothery rule that justifies this difference is
55. The property of a material that cannot be significantly changed by heat treatment is
56. A binary phase diagram of components P and Q displays an eutectoid reaction with terminal solid solutions a on the P rich side and β on the Q rich side. At the eutectoid temperature, the solubilities of Q in a and β are 5 and 90 wt% respectively. The densities of α and β phases are 9.5 and 2.49 gm/cm3 respectively.
At the eutectoid point, the alloy has α and β in the weight ratio 1 : 1. The eutectoid point occurs at composition . . . . . . . . wt % Q.
At the eutectoid point, the alloy has α and β in the weight ratio 1 : 1. The eutectoid point occurs at composition . . . . . . . . wt % Q.
57. Match the elements is Group I with their corresponding crystal structures in Group II.
Group I
Group II
P. Tungsten
1. HCP
Q. Nickel
2. Simple cubic
R. Magnesium
3. BCC
S. Polonium
4. FCC
| Group I | Group II |
| P. Tungsten | 1. HCP |
| Q. Nickel | 2. Simple cubic |
| R. Magnesium | 3. BCC |
| S. Polonium | 4. FCC |
58. Match each phase in Group 1 with a description in Group 2.
Group 1
Group 2
P. E-carbide
1. A three component eutectic of iron, iron carbide, iron phosphate found in cast iron
Q. Sigma phase
2. An embrittling compound found in ferritic stainless steel
R. E-ferrite
3. Obtained on tempering of hardened steels
S. Steadite
4. Responsible for causing the weld deposit on austenitic stainless steels to be slightly magnetic
| Group 1 | Group 2 |
| P. E-carbide | 1. A three component eutectic of iron, iron carbide, iron phosphate found in cast iron |
| Q. Sigma phase | 2. An embrittling compound found in ferritic stainless steel |
| R. E-ferrite | 3. Obtained on tempering of hardened steels |
| S. Steadite | 4. Responsible for causing the weld deposit on austenitic stainless steels to be slightly magnetic |
59. A liquid phase sintered SiC-Ni composite has a solid-solid grain boundary energy (γSiC-SiC) of 0.80 J.M-2 and a solid-liquid (γSiC-SiC) interfacial energy of 0.45 J.m-2. For a SiC grain size of 20 μm, the average interparticle (SiC-SiC) neck size (in μm) is:
60. If the slip direction is at right angle to the tensile axis, then the value of critical resolve shear stress is
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