1. Phase Diagrams Continued
Class 6 CHE 333
Phase Diagrams Continued
Prov08

2. 1085C
420C

3. Substitutional Solid Solubilty
How much one element will dissolve in another is determined by the Hume Rothery rules
Atomic radii should be within 15% of each other
Crystal structure should be the same for each element for good solubility
Electronegativities should be similar.
The valences of the atoms should be similar.
Good solubility Cu –Ni, Cu-Au; Cu r=0.128A, Ni r=0.125, Au r=0.144
Crystal structure Ti- HCP, Al - FCC
Poor soluility Na-Cl Na electronegativity 0.9, Cl 3.0
Valences – Zn 2+, Cu 1+
Only indicate solubility from these rules.
DOES NOT APPLY TO THE ELEMENTS H,C,O,N,B THESE FORM INTERSTITIAL
SOLID SOLUTIONS.

4. Iron Carbon Phase Diagram
Fe - a then g then d
912C 1394C
Steels
Eutectoid
S1 -> S2 + S3
-> a + F e3C
Peritectic
S1+L -> S2
d + L -> g
3367 SUBLIMES
Fe3C- cementite
A compound

5. Stainless Steel Phase Diagram
Ternary phase diagram for stainless steels. In this case an isothermal section at a constant
temperature is used.

6. Lever Arm Rule
Determine the AMOUNTS of each phase use the Inverse Lever Arm Rule.
Amount of solid = wa-wl/ws-wl
Amount of liquid = ws-wa/ws-wl
Amount of solid at 1300C is therefore / = 8/13 = 0.615= 61.5%
Amount of liquid at 1300C is therefore / = 5/13 = = 38.5%

7. Change Average Composition 50%
Determine the AMOUNTS of each phase use the Inverse Lever Arm Rule.
Amount of solid = wa-wl/ws-wl
Amount of liquid = ws-wa/ws-wl
Amount of solid at 1300C is therefore / = 5/13 = 0.385= 38.5%
Amount of liquid at 1300C is therefore / = 8/13 = = 61.5%

8. Microstructures and Composition

9. Lead Tin Microstructures
38.1%Pb 61.9% Sn
90 %Pb 10%Sn
70% Pb 30%Sn
50%Pb 50%Sn

10. Lead Tin Microstructures
15%Pb 85%Sn
Equiaxed Single Phase Grain Structure

11. Homework
Using the Cu-Ni phase diagram, for a Cu-Ni what are the compositions of the phases at 1400, 1300 and 1200 C and what phases would be present.
Using the Pb- Sn phase diagram,what are the compositions for points “a,c and e” on the diagram?