An alloy containing 90wtPb10wtSn is cooled from 200OC to roo

An alloy containing 90wt%Pb-10wt%Sn is cooled from 200OC to room temperature. Name the major phase in the material and give its composition at room temperature. On cooling a second phase precipitates. What temperature does the phase diagram suggests that the second phase should appear for the first time. How much of the second phase is present at room temperature?

400 300 200 100 Pb Liquidus Solidus Liquidus Solidus L A L 61.9 19 183 97.5 Solvus Solvus- B 20 60 80 40 Sn Weight percent tin (c)2003 Brooks Cole, a division of Thomson Leaming, Inc. Thomson Leaming,Mis a

Solution

By using tie line concept

from phase diagram

Beta is the major phase at room temperature=25 degree and 10 wt% Sn

its composition at room temp is 97.5 wt % Pb

at 183 degree second phase appears for first time.

amount of second phase ie.alpha= 9*100/95=9.5 %(approximately)