16 A leadtin alloy with 30 pounds of tin and 70 pounds oflea

16) A lead-tin alloy with 30 pounds of tin and 70 pounds oflead is heated to 300 degrees C and slowly cooled. What is the fraction of proeutectic alpha at 182.9 degrees C? a) 0.72 b) 0.95 c) 0.28 d) 0.55

Solution

For 70% Pb 30% Sn, a phase if formed in a+liquid range, called pro eutectic alpha.

Amount of proeutectic alpha and eutectic alpha+beata is obtained from inverse lever arm rule

Amount of pro eutectic a = 61.9-30.0/61.9-18.3 = approximatly 72% = 0.72

Answer A