(i) Explain the circumstances in which a pure liquid might solidify with the growth of dendrites rather than by the movement of a planar liquid-solid interface. [40%]

(ii) Why is it possible to obtain dendritic solidification of an alloy when the temperature increases as a function of distance ahead of the solidification front? [40%]

(iii) Which of these would reduce the tendency to form dendrites?

Large solute concentration.

Low growth rate.

Large, positive temperature gradient in the liquid ahead of the solidification front.

Small partition coefficient.