lecture 11 - ME 330 Engineering Materials Lecture 11 Heat...

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Lecture 11 Heat Treatment / Phase Transformations Stephen D. Downing Mechanical Science and Engineering © 2001 - 2010 University of Illinois Board of Trustees, All Rights Reserved ME 330 Engineering Materials
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ME 330 - Lecture 11 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 1 of 41 This Lecture . .. ± Steel Phase Diagram Review ± Reaction kinetics … what happens when time is introduced to solidification ± TTT curves ± CCT curve
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ME 330 - Lecture 11 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 2 of 41 Reminder ± Exam #1 is Thu Oct 7 th ± 1 week from Thursday ± Covers Lectures 1-10 ± Chapters 1-7, 9 ± Review session on Lecture 13 ± Phase Diagrams Lab ± Group Formal Report
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ME 330 - Lecture 11 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 3 of 41 Iron-Iron Carbide Phase Diagram ± Ferrite, α ± BCC structure ± Carbon dissolved in iron (0.02% max.) ± Soft, weak, ductile ± Austenite, γ ± High temperature phase, above 727°C ± FCC crystal structure ± Carbon dissolved in iron (2.14% max.) ± Ferrite, δ ± BCC structure ± Cementite ± Hard, strong, brittle δ , Ferrite (BCC) γ , Austenite (FCC) α , Ferrite (BCC) Cementite (Fe 3 C)
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ME 330 - Lecture 11 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 4 of 41 01 % 1000 800 600 Temperature ° C γ α + γ γ + Fe 3 C α + Fe 3 C α 1076 Steel 6.70% Fe 3 C 727 Composition (wt % C) Eutectoid Solidification ± Start with pure austenite, γ ± Eutectoid Reaction ± ± 0.76 % Carbon at 727 °C ± Develop pearlite microstructure ± Similar to eutectic microstructure from last time ± Alternating lamellae of α and Fe 3 C ± Properties intermediate between constituents () ( ) ( ) C % 7 . 6 C Fe C % 022 . 0 C % 76 . 0 3 + α γ γ γ γ γ
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ME 330 - Lecture 11 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 5 of 41 Hypoeutectoid Solidification ± Hypoeutectoid - compositions before eutectoid (%C < 0.76%) ± Start with pure austenite, γ ± α nucleates on grain boundaries ± Proeutectoid ferrite ± Upon crossing eutectoid isotherm ± Remaining austenite all turns to pearlite. ± Eutectoid ferrite ± Cementite ± Proeutectoid ferrite remains unchanged ± Further cooling will result in only minor microstructural changes 01 % 1000 800 600 Temperature ° C γ α + γ γ + Fe 3 C α + Fe 3 C α 1045 Steel 6.70% Fe 3 C 727 Composition (wt % C) α Fe 3 C α α α γ γ γ γ γ γ γ γ α α γ γ γ γ α α α
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ME 330 - Lecture 11 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 6 of 41 Hypereutectoid Solidification ± Hypereutectoid - compositions after eutectoid (%C > 0.76, %C < 2.14) ± Start with pure austenite, γ ± Fe 3 C nucleates on grain boundaries ± Proeutectoid cementite ± Upon crossing eutectoid isotherm ± Remaining austenite all turns to pearlite.
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This note was uploaded on 10/03/2011 for the course ME 350 taught by Professor Staff during the Spring '08 term at University of Illinois, Urbana Champaign.

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lecture 11 - ME 330 Engineering Materials Lecture 11 Heat...

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