Q.1
Name the process by which the migration of rough interfaces takes place?
  • a) Lateral growth
  • b) Vertical wipe
  • c) Batch growth
  • d) Continuous growth
Q.2
In the continuous growth process the driving force for solidification ΔG is given as ______
  • a) ΔG= L(ΔTi/Tm)
  • b) ΔG= L(Tm/ΔTi)
  • c) ΔG= ΔTi/(Tm*L)
  • d) ΔG= Tm/(L*ΔTi)
Q.3
The equation related to the net rate of solidification is given as_______ (K has the properties of boundary mobility)
  • a) R = K*ΔTi
  • b) R = K*ΔTi/Tm
  • c) R = K*Tm
  • d) R = K*(Tm/ΔTi)
Q.4
The surface nucleation rate governs the rate of growth normal to the interface .A theoretical treatment shows that this is proportional to_______
  • a) ΔTi
  • b) Exp (k/ΔTi)
  • c) 1/ΔTi
  • d) Exp (-k/ΔTi)
Q.5
Materials with a high entropy of melting prefer to form atomically smooth, close-packed interfaces. For this type of interface the minimum free energy also corresponds to the minimum internal energy.
  • a) True
  • b) False
Q.6
Calculate the interfacial undercooling if the melting temperature isand the latent heat of melting is given as 30kJ/kg? (Assume the driving force for solidification as 45kJ/kg?
  • a) 150K
  • b) 600K
  • c) 900K
  • d) 450K
Q.7
Calculate the extent of interfacial undercooling if the value of k (Mobility) is given as 0.05(m/ (sec*Kelvin)) and the rate of solidification(R) is given as 5m/sec?
  • a) 100K
  • b) 1000K
  • c) 200K
  • d) 2000K
Q.8
If the solid contains dislocations that intersect the S/L interface the problem of creating new interfacial steps can be circumvented. A complete theoretical treatment of this situation shows that for spiral growth the normal growth rate v and the undercooling of the interface ΔTi are related by an expression given as_______ (K material constant)
  • a) R = K(ΔTi)
  • b) R = K(ΔTi)3
  • c) R = K(ΔTi)2
  • d) R = K/(ΔTi)2
Q.9
In solidification it is quite common for materials showing faceting to solidify as two crystals in twin orientations.
  • a) False
  • b) True
Q.10
In pure metals solidification is controlled by the rate at which the latent heat of solidification can be conducted away from the solid/liquid interface. Which among the following equation satisfies the heat flow and the interface stability? (Kl, Ks are respective thermal conductivities of liquids and solids, L the latent heat of fusion per unit volume, v growth rate).
  • a) KsTs = Kl*Tl /(v*L)
  • b) KsTs = Kl*Tl – v*L
  • c) KsTs = Kl/(Tl +v*L)
  • d) KsTs = Kl*Tl +v*L
Q.11
Let us now take a closer look at the tip of a growing dendrite. The situation is different from that of a planar interface because heat can be conducted away from the tip in three dimensions. As a result of the Gibbs-Thomson effect equilibrium across a curved interface occurs at an undercooling ΔTr below Tm given by______ (Latent heat of fusion per unit volume)
  • a) ΔTr = 2γTm/(L*r)
  • b) ΔTr = 2Tm/(L*r)
  • c) ΔTr = 2Tm/(L*γ*r)
  • d) ΔTr = 2γTm/L
Q.12
Let’s take the tip of a growing dendrite. Here in this case it can be seen that the tip velocity tends to zero for a particular value of r known as______
  • a) Critical radius
  • b) Open radius
  • c) Closed radius
  • d) Extended radius
Q.13
When the solidification takes place from the mould wall (cooler than melt), this leads to the heat conduction through the solids. However the heat flow into the liquid arises if a certain condition is satisfied. Which among the following corresponds to the same?
  • a) If the liquid is supercooled below Tm
  • b) If the liquid is brought in contact with mould wall
  • c) If the liquid is supercooled at any temperature
  • d) Superheated above Tm
Q.14
Calculate the value of latent heat of fusion per unit volume if the thermal conductivities of solid and liquid are given asandkW/mK respectively and the temperature gradient of liquid and solid are given as 2K/m and 1.5K/m respectively? (Assume the rate of growth as 5m/s)
  • a) 0
  • b) 5
  • c) 25
  • d) 100
Q.15
The maximum velocity at the tip of growing dendrite occurs when ______ (r* is the critical radius)
  • a) R = 2r*
  • b) R = 3r*
  • c) R = r*
  • d) R = 4r*
0 h : 0 m : 1 s