Class 5

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Class 5

• Phase Diagrams Continued

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(D2.34), Cu-Au(D11) Cu
  r0.128A, Ni r0.125, Au r0.144
• Crystal structure Ti- HCP, Al - FCC
• Poor solubility 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.

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Iron Carbon Phase Diagram
Liquid
1538C
3367 SUBLIMES
Fe - a then g then d 912C 1394C
g L

• Steels
• Eutectoid
• S1 -gt S2 S3
• -gt a F e3C
• Peritectic
• S1L -gt S2
• d L -gt g

Fe3C- cementite A compound
g Fe3C
a Fe3C
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Stainless Steel Phase Diagram
Ternary phase diagram for stainless steels. In
this case an isothermal section at a
constant temperature is used.
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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
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Change Average Composition 50
Determine the NEW 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
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Microstructures and Composition
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Lead Tin Microstructures
38.1Pb 61.9 Sn
90 Pb 10Sn
70 Pb 30Sn
50Pb 50Sn
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Lead Tin Microstructures
15Pb 85Sn
Equiaxed Single Phase Grain Structure
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Homework

• Using the Cu-Ni phase diagram, for a 50-50 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?
• Due next Monday.