The GATE Grind

GATE 2026 MT – Question 34

Metallurgical Thermodynamics · Phase equilibria and phase diagrams · 1 mark · Numerical answer

For an equilibrium phase diagram of a binary A-B alloy at a constant pressure as shown in the figure, the degree of freedom at ‘X’ is (answer in integer) _______________.

Diagram for GATE 2026 MT question 34

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: 1 to 1

Explanation

Point X lies between the liquidus and solidus, so two phases coexist: solid and liquid. At fixed pressure, the reduced Gibbs phase rule is $F=C-P+1$.

For two components and two phases, $F=2-2+1=1$. The answer is **1**. Changing the overall alloy composition within this region changes phase amounts rather than adding a phase-equilibrium degree of freedom.