Question

- 20 40 Composition (at"% Sn) 60 327°C Liquid 500 232°C 183°C Temperature (°C) Temperature (°F) 19.3 61.9 20 60 80 100 (Sn) Composition (wt% Sn) A lead-tin alloy of composition Pb-30%Sn is slowly cooled from a temperature of 300°C. Use the phase diagram given to determine... 1. Is the alloy hypo- or hyper-eutectic? 2. What is the composition of the first solid phase to form during freezing? 3. What is the composition of each phase present at 100 °C? 4. What is the amount of each phase present at 100°C? 5. What is the composition of each microconstituent present at 182°C? 6. What is the amount of each microconstituent present at 182°C?

Answer 1

sinu snl is less than eutectic (ie 6lig utt Sn) so it is hypo-eutectic 2) At 30 wt. sn first solid phase will be a composition 14 wty sn. 3) At looc & & ß phases are Present a = 6 wt T. Sn. CB - 99.2 wt% Sn. 634 30 cot's so 99.2 wa = 99.2-36 - 0.7424 99.2 - 6 or 72.24 7. 6119 rooc --- 4) wro 5.) WB = 30 - 6 – 0.2575 on 25.75% 99.2-6 At 182, there will be tooteclat Primary a, & Eutectic & & ß. Primary & - 18.3 wt% Sn. Ceutectic a = 18. 3 wt Y. Su CB 97.8 wt & Su Wenn a = 61.9-30 - 0.73 16 61.9-18.3 6) 6 Wprimary a = 3 0 - 18 = .3 Wenteche a = 0.2683 61.9-18.3 WB = 30-18.3 - 0.1471 97.8- 18.3