EM-Unit-1-cooling curve

UNIT I CONSTITUTION OF ALLOYS

1. COOLING CURVE Unit -1

2. Cooling curve The solidification of molten metal is plotted as a graph is called cooling curve. X – axis – Time Y – axis -Temperature

3. Types of cooling curve Cooling curve for Pure metal or compound (liquid , solid) Cooling curve of a binary solution (liquid, solid ,liquid + solid) Cooling curve of a binary Eutectic system (liquid, solid ,liquid + solid)

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5. 1.Cooling curve for Pure metal or compound PQ -- Molten Metal Looses Its Temp Q – Starting Point For Crystal Structure QR –Latent heat is liberated Temp remains constant RS – Solid metal formation

6. 2.Cooling curve of a binary solution PQ -- Molten Metal Looses Its Temp Q – Starting Point For Crystal Structure QR –The slope of cooling curve will change due to evolution of latent heat of crystallization. RS – Solid metal formation

7. 3.Cooling curve of a binary Eutectic system PQ -- Molten Metal Looses Its Temp Q – temperature drops along QR and crystallization of one component starts. R –the liquid composition reaches such level that two components crystallise simultaneously from the solution and temperature remains constant until all the liquid solidifies. ST – Solid metal formation

8. CONSTRUCTION OF PHASE DIAGEAMS

9. Interpretation of phase diagrams Using a phase diagram, one can obtain at least the following three transformations. The phases that are present The composition of each phase The amount of each phase present.

10. Types of Equilibrium Phase Diagram Plot the composition of phases as a function of temperature in any alloy system under equilibrium conditions. Phase diagrams for complete solid solubility Phase diagrams for partial solid solubility Phase diagrams containing reactions

11. 1. Phase diagrams for complete solid solubility Two elements are completely soluble in each other in both in liquid and solid states is known as isomorphous system. Examples Cu-Ni System Sb-Bi System Au-Ag System Cu-Au System

12. 2. Phase diagrams for partial solid solubility If the two metals A and B are not completely soluble through all ranges in composition, the second phase will form at grain boundaries. Examples Cu-Ag System Al-Cu System

13. 3. Phase diagrams containing reactions Eutectic reaction Peritectic reaction Eutectoid reaction Peritectoid reaction

14. Eutectic reaction

15. Peritectic reaction

16. Eutectoid reaction

17. Peritectoid reaction

18. Summary