Question

The solidification of an alloy starts in a phase diagram from

• A. Liquidus line
• B. Solidus line
• C. At equilibrium
• D. At freezing point

Hint:

For alloys: {Liquidus = start of solidification}, {Solidus = end of solidification}.

Answer 1

The Correct Option is A

Step 1: Understanding solidification in alloys.
Solidification of an alloy begins when the first solid phase starts to form from the liquid during cooling. In a phase diagram, this transformation is represented by a specific boundary line.
Step 2: Role of the liquidus line.
The liquidus line separates the fully liquid region from the liquid + solid region. As soon as the temperature crosses this line during cooling, solidification begins.
Step 3: Elimination of other options.
(B) Solidus line: Represents the completion of solidification, not the beginning.
(C) At equilibrium: Equilibrium is a condition, not a boundary for phase change.
(D) At freezing point: Pure metals freeze at a point, but alloys solidify over a range of temperatures.
Step 4: Conclusion.
Hence, the solidification of an alloy starts from the liquidus line.