The GATE Grind

GATE 2024 MT – Question 41

Physical Metallurgy · Nucleation solidification and transformations · 2 marks · Multiple choice

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.

Diagram for GATE 2024 MT question 41
  1. less than
  2. greater than
  3. same as
  4. independent of

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (A) less than

Explanation

The supplied phase diagram has a positive liquidus slope and solid preferentially takes up B.

Liquid adjacent to the interface is therefore depleted in B.

Its local liquidus temperature is below the far-field liquidus and rises with distance, as shown.

Thus region X has **less B than the initial average, A**.