Question

Problem 1 (Chapter 10). For a lead-tin alloy of composition 45 wt% Sn - 55 wt% Pb at 180°C, do the following (except (e)); (a) Determine the mass fractions of the a and 3 phases. (b) Determine the mass fractions of primary (pro-eutectic) a and eutectic micro-constituents. (c) Determine the mass fraction of eutectic a. (d) For a photomicrograph of the alloy shown below, please label all micro-constituents and indicate their approximate compositions. (e) Draw the sketch of a photomicrograph of the alloy at 185°C based on the one in (d). Composition % 560 60 100 327°C 600 300 Liquid 500 2320 . 200 183°C 400 Temperature 183 61.9 Temperature (72 978 300 100 200 100 20 100 40 60 Composition wtSA Adapted from Bray Aloy Prase Diagrams and edition to a 1 B. Massalok(Editor-in-Chief)1990 Reprinted by permission of ASM raional Materiais Park OH Phi IS

Answer 1

X+L BtL TA 183C B s 'E B - 18.37.87 61.9% 591 97.8% 5n 1451.59 %sn +55% lb s is our sample point a mass fraction of a SB AB [By in verse lever rule] 97.8-45 97.8-18:3 = 0.664 mass fraction of ß AS AB 45-18.3 97.8.18.3 = 0.336 a =

b mass fraction of primary a Glog-45 Glog-18.3 - 0.387 SE AE = mass fraction of entectie mixture 45- 183 Glig-18.3 - AS AE 6.613 mass fraction of entectic a = 0.451 E B AB 97.8-Glig 97.8-18.3 the micrograph a In the Given photo microstrueture is composed of primary lead- rich a phase (large dark region with in a lommellar entectic structure consisting of tin-rich ß phase (light layers) and a phase (dark layer). Kod approximate composition (50%sn +501.pb) a lead-rich