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Interactive MENG 426 Lab Tutorials Experiment (4) Eutectoid, Hyper- & Hypo- Alloys

The American University in Cairo Mechanical Engineering Department MENG 426: Metals, Alloys & Composites. Interactive MENG 426 Lab Tutorials Experiment (4) Eutectoid, Hyper- & Hypo- Alloys. Prepared by Eng. Moataz M. Attallah Fall 2002. Outline. Review: phase diagrams & invariant reactions

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Interactive MENG 426 Lab Tutorials Experiment (4) Eutectoid, Hyper- & Hypo- Alloys

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  1. The American University in CairoMechanical Engineering DepartmentMENG 426: Metals, Alloys & Composites Interactive MENG 426 Lab Tutorials Experiment (4) Eutectoid, Hyper- & Hypo- Alloys Prepared by Eng. Moataz M. Attallah Fall 2002

  2. Outline • Review: phase diagrams & invariant reactions • Fe-Fe3C System: major features • Eutectoid reaction • Controlling parameters • Specimens • Lab report

  3. Review: Phase diagrams Equilibrium Diagrams • Phase Diagram: Graphical representation for the material (pure/mixture/binary alloy/tertiary alloy) within a temperature range at a range of compositions, showing the existing phases & any transformation reactions. • Equilibrium cooling: slow cooling that does not deform the structure.

  4. Eutectic Eutectoid Peritectic Peritectoid Montectic Review: Invariant reactions • Phase transformation reactions that take place at a specific temperature and composition (zero degree of freedom). • Types:

  5. Fe-Fe3C SystemIron-Iron Carbide System

  6. Fe-Fe3C System phases (1)Iron-Iron Carbide System • Fe3C • Cementite or Iron Carbide • 6.67% C, 93.33% Fe • Stoichiometric Intermetallic • Ionic & covalent bonding • Hard and brittle

  7. Austenite • Gamma iron, FCC, ISS • Maximum solubility 2% http://info.lu.farmingdale.edu/depts/met Fe-Fe3C System phases (2)Iron-Iron Carbide System

  8. Ferrite • Alpha iron, BCC, ISS • Maximum solubility 0.02% http://info.lu.farmingdale.edu/depts/met Fe-Fe3C System phases (3)Iron-Iron Carbide System

  9. Delta Ferrite • Alpha iron, BCC, ISS • Maximum solubility 0.1% Fe-Fe3C System phases (4)Iron-Iron Carbide System

  10. Ledeburite • Eutectic (Fe3C+ ) • Cast iron eutectic Fe-Fe3C System phases (5)Iron-Iron Carbide System

  11. Pearlite Eutectoid Reaction

  12. Eutectoid Microstructure

  13. Hypo/Eutectoid/Hyper

  14. Hyper- & Hypo-Eutectoid

  15. Hypo- & Hyper- Eutectoid

  16. Objective • Get acquainted with Fe-Fe3C phase diagram. • Study the effect of the eutectoid invariant reaction on steel microstructure. • Differentiate between eutectoid, hypo-eutectoid, and hyper-eutectoid microstructures. • Study the effect of cooling on microstructure

  17. Specimens • Specimen (1): 0.35%C, etched for 15 sec. in 2% HNO3 alchoholic solution (nital) • Specimen (2): 0.8% C, furnace cooled, ground and polished with diamond paste and finishing with a 1 micron grade, followed by etching with nital. • Specimen (3): same as specimen (2), with air-cooling • Specimen (4): 1.3%C etched in nital

  18. Lab Report Required: • A "neat" sketch for the viewed microstructures. • Describe the phase transformation for each specimen from the liquid state to the solid state with the aid of the (Fe-Fe3C) phase diagram.

  19. Questions?

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