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GATE 2019 ME (ME2) – Question 44

Engineering Materials · Phase diagrams and heat treatment · 2 marks · Multiple choice

The binary phase diagram of P and Q is shown. Alloy X contains 60 wt% P and 40 wt% Q and cools from liquid to solid. Find solid and liquid weight percentages respectively at 1250°C.

Diagram for GATE 2019 ME (ME2) question 44
  1. 77.8% and 22.2%
  2. 22.2% and 77.8%
  3. 68.0% and 32.0%
  4. 32.0% and 68.0%

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Correct answer: (B) 22.2% and 77.8%

Explanation

The tie-line liquid and solid compositions are 32 and 68 wt% Q. Lever rule gives $f_s=(40-32)/(68-32)=8/36=22.2\%$. Liquid fraction is 77.8%. **B**.