Class 6 CHE 333
Phase Diagrams Continued
Prov08
Copper Zinc Phase Diagram
1085C
420C
Peritectic reaction Liquid + solid 1 -> solid 2.
Eutectoid reaction Solid 1 -> solid 2 + solid 3
Maximum solid solubilty of zinc in copper is 38% at around 450C
Substitutional Solid Solubilty
How much one element will dissolve in another is determined by the Hume Rothery rules
1.
Atomic radii should be within 15% of each other
2
Crystal structure should be the same for each element for good solubility
3
Electronegativities should be similar.
4
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.
Iron Carbon Phase Diagram
1538C
Fe - a then  then d
912C 1394C
Steels
Eutectoid
S1 -> S2 + S3
-> a + F e3C
Peritectic
S1+L -> S2
d + L -> 
3367 SUBLIMES
Fe3C- cementite
A compound
Stainless Steel Phase Diagram
Ternary phase diagram for stainless steels. In this case an isothermal section at a constant
temperature is used.
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 53-45 / 58-45 = 8/13 = 0.615= 61.5%
Amount of liquid at 1300C is therefore 58-53 / 58-45 = 5/13 = 0.385 = 38.5%
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 50-45 / 58-45 = 5/13 = 0.385= 38.5%
Amount of liquid at 1300C is therefore 58-50 / 58-45 = 8/13 = 0.615 = 61.5%
Microstructures and Composition
Lead Tin Microstructures
90 %Pb 10%Sn
70% Pb 30%Sn
38.1%Pb 61.9% Sn
50%Pb 50%Sn
Lead Tin Microstructures
15%Pb 85%Sn
Equiaxed Single Phase Grain Structure
Homework
• Using the Cu-Ni phase diagram, for a 5050 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?