Week8Ch10

Week8Ch10 - Jiuhua Chen, Associate Professor chenj@fiu.edu...

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Jiuhua Chen, Associate Professor henj@fiu.edu chenj@fiu.edu Tel. 348-3140 ffice EC 3471 and Office EC 3471 and VH 140, UP campus Office Hours: M11:00-12:00 F 10:00-11:00 or by appointment Course web site: http://web.eng.fiu.edu/~chenj/fall2008EGN3365 Chapter 10 - 1
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Chapter 10: hase Transformations 0 1 Introduction: ISSUES TO ADDRESS Phase Transformations 10.1 Introduction: ISSUES TO ADDRESS. .. Transforming one phase into another takes time. Fe γ (Austenite) Eutectoid transformation C CC Fe 3 C (cementite) α + CC) How does the rate of transformation depend on me and FCC (ferrite) (BCC) time and T ? How can we slow down the transformation so that we can engineering non-equilibrium structures? Are the mechanical properties of non quilibrium Chapter 10 - 2 Are the mechanical properties of non-equilibrium structures better?
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Learning Objectives Make a schematic fraction transformation- ersus- garithm of time plot for a typical versus logarithm of time plot for a typical solid-solid transformation; cite the equation that describes this behavior. Briefly describe the microstructure for y each of the following microconstituents that are found in steel alloys: fine pearlite, coarse pearlite, spheroidite, bainite, martensite, and tempered martensite. Chapter 10 - 3
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Learning Objectives Cite the general mechanical characteristics for each of the following microconstituents: fine pearlite, coarse pearlite, spheroidite, bainite, martensite, and tempered martensite. Now, in rms of microstructure (or crystal structure) terms of microstructure (or crystal structure), briefly explain these behaviors. Given the isothermal transformation (or continuous cooling transformation) diagram for ome iron arbon alloy design a heat treatment some iron-carbon alloy, design a heat treatment that will produce a specified miscrostructure. Chapter 10 - 4
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Homework assignments Question and Problems 10.3 uestion and Problems 10.6 Question and Problems 10.6 Question and Problems 10.14 Question and Problems 10.15 Question and Problems 10.20 Question and Problems 10.23 Question and Problems 10.34 Question and Problems 10.D4 Homework assignments will be discussed in Wednesday Class. (TA: Shadab Siddiqui, EC2767 Tel. 305-336-7716) Chapter 10 - 5 (q , )
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Phase Transformations 10.2 Basic Concepts iffusion- ependent transformation 1 (no composition Diffusion dependent transformation 1 (no composition change): solidification… Diffusion-dependent transformation 2 (composition hange): eutectoid reaction change): eutectoid reaction… Diffusionless transformation: matensitic transition 10.3 The Kinetics of Phase Transformations Nucleation – nuclei (seeds) act as template to grow crystals – for nucleus to form rate of addition of atoms to nucleus must be faster than rate of loss – once nucleated, grow until reach equilibrium Chapter 10 - 6
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Solidification: Nucleation Processes • Homogeneous nucleation – nuclei form in the bulk of liquid metal – requires supercooling (typically 80-300°C max) 3 4 V=3/4 π r 3 , S=3 π r 2 υ π G r G V 3 G v = volume free energy difference γ π = 2 4 r G S γ = surface free energy Chapter 10 - 7
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Week8Ch10 - Jiuhua Chen, Associate Professor chenj@fiu.edu...

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