1. Cu – 30wt% Zn (a – Brass) – Cold rolled and recrystallized
2. Al – 12wt% Cu – as cast
3. Al – 33wt% Cu – as cast (eutectic)
4. Sn – 25wt% Cu – slow cooled from liquid
Al – 12wt% Cu
Al – 33wt% Cu

Al – 12% Cu
Al – 33% Cu
Cu – 30wt% Zn

Cu – 30% Zn
Sn – 25wt% Cu

Sn – 25% Cu
Determination of Bulk Composition from SEM Image Procedure
Import the SEM picture into this file on a new slide; adjust the size as needed.
Copy and paste the red grid on top of the picture. Move the grid to a random spot so that all the intersections are on the image
Count the number of intersections that are on the Al2Cu phase (lighter phase)
Calculate the percent of intersections on the Al2Cu phase (number on the Al2Cu divided by the total number of intersections). This is the same as the volume% of the Al2Cu. So the volume % of alpha is just 1-Vol% Al2Cu
Convert volume percent to weight percent using the densities given on the next page (assume 100 ml total for the sample)
Use the lever rule along with the phase diagram and assumptions on the next page to estimate/calculate the bulk composition from the weight percent.
Density of Al2Cu is 4.34 g/cm3
Density of alpha phase is 2.8 g/cm3
Assume composition of alpha is 5 wt% Cu
Assume composition of Al2Cu is 53 wt% Cu
Total intersections = ?
Al2Cu intersections = ?
Vol of Al2Cu = ?
Vol of α Al = ?
Wt of Al2Cu = ?
Wt of α Al = ?
Total weight is = ?
Wt% of Al2Cu = ?
Wt% of α Al = ?
Bulk composition is = Co=? , CB = 53% Cu, CA = 5% Cu
Wt% α Al = (CB-Co)/(CB-CA)
α =5% Cu
Al2Cu = 53% Cu
estimate/calculate the bulk composition from the weight percent.

Leave a Reply