For a solid embryo in contact with a perfectly flat mould wall as shown in the schematic, the wetting angle $\theta$ is __________ degrees. (Round off to one decimal place). Given: Surface tension between liquid and mould wall = $0.35 \text{ J.m}^{-2}$ Surface tension between solid and mould wall = $0.02 \text{ J.m}^{-2}$ Surface tension between liquid and solid = $0.40 \text{ J.m}^{-2}$
Given:
γLM = 0.35 J/m²
γSM = 0.02 J/m²
γLS = 0.40 J/m²
Young’s equation:
cosθ = (γLM − γSM) / γLS
cosθ = (0.35 − 0.02) / 0.40 = 0.33 / 0.40 = 0.825
θ = cos−1(0.825) = 34.3°
Important Questions from Solidification Directional Solidification
A hypothetical binary eutectic phase diagram of A – B is shown below. An alloy with 5 wt.% B solidifies with no convection. Assuming steady state, the critical temperature gradient (in K $mm^{-1}$) required to maintain planar solidification front is: ________ (round off to nearest integer).
Given:
Diffusivity of B in liquid = $10^{-9}$ $m^2$ $s^{-1}$
Velocity of solidification front = 4 $\mu m$ $s^{-1}$The constitutional undercooling condition for a hypothetical binary alloy of A with solute B during solidification is shown in the figure along with its binary phase diagram. Based on these two schematics, one can conclude that the solute concentration in region X will be _______________ the average composition of the initial liquid phase.
In continuous casting of steel, mould flux is used for ______________
The critical radius (in $nm$, rounded off to one decimal place) of nickel nucleus during solidification at $1673 \text{ K}$ is ________.
Given: Enthalpy of fusion of nickel = $2.65 \times 10^9 \text{ J.m}^{-3}$;
Liquid-solid interfacial energy = $0.5 \text{ J.m}^{-2}$, and
Equilibrium melting temperature of nickel = $1728 \text{ K}$.
Single crystal turbine blades of nickel-based superalloys for aero-engines are manufactured using:
