If a Pb-Sn liquid solution with 61.9% (Wt%) Sn is cooling down slowly from 200 d
ID: 530071 • Letter: I
Question
If a Pb-Sn liquid solution with 61.9% (Wt%) Sn is cooling down slowly from 200 degree C to 183 degree C, what new phases will be formed? What is Sn weight percentage in each of the newly formed phases? What is the weight ratio between the newly formed phases? Will the original liquid solution completely transform to the new phases at 183 degree C? If the Pb-Sn liquid solution with 40% (Wt%) Sn is cooling down slowly from 300 degree C to room temperature, please use schematic graph to show what will the microstructure in the final product looks like?Explanation / Answer
b)Cooling down from 200 to 1830 C.
So, TE= 1830C
Just above TE,
C = 18.3 wt% Sn
CL= 61.9 wt% Sn
W=S/(R+S)= 50 wt%
WL= 100-50 %= 50%
W/WL = 1
Just below TE:
C= 18.3 wt% Sn
C= 97.8 wt% Sn
W =S/(R+S) = 73 wt%
W= 27 wt%
W/W = 2.70
c)For a 40 wt% Sn-60 wt% Pb alloy at 300°C,
CO= 40 wt% Sn
C= 6 wt% Sn
CL= 14 wt% Sn
W= (CL-Co)/ (CL-C) = 3.25 wt%
WL = 96.75 wt%