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Chapter 4 Equilibrium Phase Diagrams and The Iron-Carbon system

Chapter 4 Equilibrium Phase Diagrams and The Iron-Carbon system. Kanchala Sudtachat. Phases. A phases is simply a form of material possessing a characteristic structure and properties. A phases has a definable structure, a uniform and identifiable chemistry.

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Chapter 4 Equilibrium Phase Diagrams and The Iron-Carbon system

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  1. Chapter 4Equilibrium Phase Diagrams and The Iron-Carbon system Kanchala Sudtachat

  2. Phases • A phases is simply a form of material possessing a characteristic structure and properties. • A phases has a definable structure, a uniform and identifiable chemistry. • And distinct boundaries or interfaces that separate it from other different phases.

  3. Equilibrium Phase Diagrams • is a graphic mapping of the natural tendencies of a material or a material system. • There are three primary variable to be considered: temperature, pressure and composition

  4. Pressure-Temperature (P-T) diagram • Diagram maps the stable form of water for various conditions. • The region boundaries denote the melting and boiling point. • It has important to make freeze drying.

  5. Temperature-Composition(T-C) diagram • At atmospheric pressure and variations more likely to occur in temperature and composition.

  6. Cooling Curves • The equilibrium phase diagram is collective presentation of cooling-curve data for an entire range of alloycompositions

  7. Solubility Studies • Can ice retain some salt in a single phase solid solution? • Can solid salt hold some waterand remain a single-phase? • How much, and does the amount vary with temperature? • We called solubility limit.

  8. Lead-tin equilibrium phase diagram Solvus line: เส้นแบ่งระหว่างของแข็งเฟสเดียวและของแข็ง 2 เฟส

  9. Complete solubility in both liquid and solid states • Liquidus line – เหนือเส้นนี้เป็นสารละลายในเฟสเหลว • Solidus line – ด้านล่างของเส้นนี้เป็นสารละลายในเฟสของแข็ง Freezing range: Between the liquidus and Solidus

  10. Partial solid solubility • At the point of max solubility, 183oC • Lead can hold up to 19.2 wt% • If T is decreased, the amount of solute that can be held in solution decreased.

  11. Insolubility

  12. Utilization of diagram • ที่อุณหภูมิและส่วนผสมหนึ่งๆนั้นจะบอกได้ว่า • The phase presentเป็นเฟสของอะไร – ของแข็ง?, ของเหลว?, ของแข็งโครงสร้าง? • The composition of each phaseปริมาณของแต่ละเฟส – ของแข็ง ?%, ของเหลว ?% • The amount of each phase presentส่วนผสมในแต่ละเฟส – ในของแข็งมีสาร A อยู่ ?% สารB อยู่ ?%, ในของเหลวมีสาร A อยู่ ?% สารB อยู่ ?%

  13. Equilibrium Phase Diagrams: T-C Diagram ปริมาณของแต่ละเฟส – ของแข็ง ?%, ของเหลว ?%

  14. Equilibrium Phase Diagrams: T-C Diagram • ส่วนผสมในแต่ละเฟส –ในของเหลวมีสาร A อยู่ ?% สารB อยู่ ?% a – S2 x 100% L2 – S2

  15. Three-phase reactions

  16. Peritectic Eutectic Eutectoid Iron-Carbon Equilibrium Diagram • Steel, compose primarily of iron and carbon

  17. Iron-Carbon Equilibrium Diagram • a body-cubic solid that is stable down to 1394oC, know as delta-ferrite. • From 1394oC to 912oC (FCC), know as austenite. • Alpha-ferrite (BCC) below 912oC

  18. Iron-Carbon Equilibrium Diagram • At 1495oC, a peritectic reaction. • At 1148oC, a eutectic with composition of 4.3% carbon • 2.11% carbon are classified by the general term cast iron • At 727oC, a eutectoid with composition of 0.77% carbon. Alloy with less than 2.11% carbon, know as steels

  19. Steels and the simplified iron-carbon diagram • The key transition will be the conversion of austenite to the two-phase ferrite plus carbide mixture.

  20. Steels and the simplified iron-carbon diagram • Pearlite (ferrite + cementite) Eutectoid composition (0.77%C) Austenite0.77%C; FCC Ferrite0.02%C; BCC + Cementite6.67%C

  21. Steels and the simplified iron-carbon diagram • Hypoeutectoid steels (ferrite + pearlite) less than eutectoid composition • Hypereutectoid steels (cementile + pearlite) greater than eutectoid composition

  22. Cast Irons • Iron-carbon alloys with more than 2.11% • Wide variety properties. • Contains iron, carbon, silicon, manganese, sulfur, phosphorous • อาจทำให้เกิด Graphite หรือ Cementite • Graphite form by slow cooling • Cementite form by fast cooling

  23. Cast Irons

  24. Graphite เย็นตัวลงช้าๆ ปริมาณคาร์บอน C, Si สูง ใช้เวลาบ่มตัว มีส่วนผสมของ S, P, Al, Mg, Sn, Cu, Co Cementite เย็นตัวลงเร็ว ปริมาณคาร์บอน C, Si ต่ำ มีส่วนผสมของ Ti, V, Cr, Zr, Mn, Mo Cast Irons

  25. Gray Cast Iron 0.5-4.0%C, 1.0-3.0%Si, 0.4-1.0%Mn ผลของ Graphite ทำให้ Brittle Excellent compressive strength Excellent machinability Good resistance to adhesive wear Outstanding vibration damping Cast Irons

  26. White Cast Iron 1.8-3.6%C, 0.5-1.9%Si, 0.25-0.8%Mn ผลของ Cementite ทำให้ Very hard & brittle High abrasion resistance Cast Irons

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