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Week12  Phase Diagram @ Www.07 Met.Tk
Week12  Phase Diagram @ Www.07 Met.Tk
Week12  Phase Diagram @ Www.07 Met.Tk
Week12  Phase Diagram @ Www.07 Met.Tk
Week12  Phase Diagram @ Www.07 Met.Tk
Week12  Phase Diagram @ Www.07 Met.Tk
Week12  Phase Diagram @ Www.07 Met.Tk
Week12  Phase Diagram @ Www.07 Met.Tk
Week12  Phase Diagram @ Www.07 Met.Tk
Week12  Phase Diagram @ Www.07 Met.Tk
Week12  Phase Diagram @ Www.07 Met.Tk
Week12  Phase Diagram @ Www.07 Met.Tk
Week12  Phase Diagram @ Www.07 Met.Tk
Week12  Phase Diagram @ Www.07 Met.Tk
Week12  Phase Diagram @ Www.07 Met.Tk
Week12  Phase Diagram @ Www.07 Met.Tk
Week12  Phase Diagram @ Www.07 Met.Tk
Week12  Phase Diagram @ Www.07 Met.Tk
Week12  Phase Diagram @ Www.07 Met.Tk
Week12  Phase Diagram @ Www.07 Met.Tk
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Week12 Phase Diagram @ Www.07 Met.Tk

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  • 1. Phases present L α ferrite δ Bcc structure Bcc structure Ferromagnetic Paramagnetic Fairly ductile γ austenite Fe3C cementite Fcc structure Orthorhombic Non-magnetic Hard Reactions ductile brittle Peritectic L + δ = γ Max. solubility of C in ferrite=0.022% Eutectic L = γ + Fe3C Max. solubility of C in austenite=2.11% Eutectoid γ = α + Fe3C
  • 2. Steel is an interstitial solid solution of carbon in iron. Theoretically steel has a maximum of 2.11% carbon. In practice, the amount of carbon rarely exceeds 0.8% Classification/Nomenclature Low carbon steels up to 0.2%C AISI 1020: Last two numbers indicate Medium carbon steels 0.2-0.4%C Amount of carbon :0.2%C 10 indicates plain carbon steel High carbon steels >0.4% C AISI 4340: 0.4%C 43 indicates alloy steel
  • 3. IRON-CARBON (Fe-C) PHASE DIAGRAM • 2 important T(°C) 1600 points δ -Eutectic (A): 1400 L L ⇒ γ + Fe 3 C γ+L γ A 1200 1148°C L+Fe 3 C -Eutectoid (B): (austenite) R S Fe 3 C (cementite) γ ⇒ α + Fe 3 C 1000 γ γ γ γ γ+Fe 3 C 800 α+ +γ α γ B 727°C = T eutectoid R S 6 00 α+Fe 3 C 4 00 0 1 2 3 4 5 6 6.7 (Fe) 0.77 4.30 C o , wt% C 120 µm Result: Pearlite = Fe 3 C (cementite-hard) C eutectoid alternating layers of α and Fe 3 C phases. α (ferrite-soft) (Adapted from Fig. 9.24, Callister 6e. (Fig. Adapted from Fig. 9.21,Callister 6e. (Fig. 9.21 adapted 9.24 from Metals Handbook, 9th ed., Vol. 9, from Binary Alloy Phase Diagrams, 2nd ed., Metallography and Microstructures, American Vol. 1, T.B. Massalski (Ed.-in-Chief), ASM International, Society for Metals, Materials Park, OH, Materials Park, OH, 1990.) 1985.)
  • 4. IRON-CARBON (Fe-C) PHASE DIAGRAM BCC crystal structure FCC crystal structure Note: δ phase is also called δ ferrite and is a BCC phase 1
  • 5. ALLOYING STEEL WITH MORE ELEMENTS • Teutectoid changes: • Ceutectoid changes: (wt%C) 0.8 (°C) 1200 Ti Si Mo W 0.6 Ni 10 00 Cr T Eutectoid C eutectoid Cr 0.4 Si 8 00 Mn Mn 0.2 W Ti Mo 600 Ni 0 0 4 8 12 0 4 8 12 wt. % of alloying elements wt. % of alloying elements
  • 6. Above, a syntectic reaction lurks within the diagram. This is a rare beast among alloy systems, occurring in systems like K-Zn, Na-Zn, K-Pb, Pb-U and Ca-Cd. The pertinent reaction is: L1 + L2 -> alpha

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