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GATE 2026 MT – Question 19

Physical Metallurgy · Heat treatment and recrystallization · 1 mark · Multiple choice

Which one of the following options is correct? For Al - 4 % Ag alloy (composition in atom %), the correct sequence of operations involved in precipitation hardening is:

  1. Quenching → Aging → Solution treatment
  2. Solution treatment → Aging → Quenching
  3. Aging → Solution treatment → Quenching
  4. Solution treatment → Quenching → Aging

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Show answer and explanation

Correct answer: (D) Solution treatment → Quenching → Aging

Explanation

Solution treatment dissolves the solute-rich phases. Rapid quenching then retains a supersaturated solid solution, preventing extensive equilibrium precipitation. Controlled aging allows a fine dispersion of strengthening precipitates to form. Hence **solution treatment→quenching→aging, D**. Aging before quenching cannot create the same supersaturated starting condition.