Introduction to the Science and Engineering of Materials
Introduction to the Science and Engineering of Materials MSE 2090
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This 19 page Class Notes was uploaded by Jamison Kirlin on Monday September 21, 2015. The Class Notes belongs to MSE 2090 at University of Virginia taught by James Groves in Fall. Since its upload, it has received 65 views. For similar materials see /class/209589/mse-2090-university-of-virginia in Materials Science Engineering at University of Virginia.
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Date Created: 09/21/15
CHAPTER 10 PHASE TRANSFORMATIONS ISSUES TO ADDRESS 0 Transforming one phase into another takes time YD Eu tectoid Fe 30 transformation cementite Austenite 0L ferrite How does the rate of transformation depend on time and T 0 How can we slow down the transformation so that we can engineering nonequilibrium structures 0 Are the mechanical properties of nonequilibrium structures better Chapter 101 FRACTION OF TRANSFORMATION Fraction transformed depends on time 1 Avrami Eqn y Adapted from Z ktn Fig10191 e fraction y 1 e xed 0 t 639 transformed time A T t05 3909 t 0 Transformation rate depends on T activ tion energy Ex recrycstalcl igaction of Cu Adapted from Fig 0 0 o0 102 Caster6e 1 N YM vs 8516quot q Fig102adapted r b u AeQ 10 from BF Decker and t D Harker 05 50 quotRecrystallization in Rolled Copperquot 0 4 Trans AIME 188 1 10 102 1950 p 888 Chapter 10 2 10 log t min 0 r often small equil not possible TRANSFORMATIONS amp UNDERCOOLING Eutectoid transf FeC System y gt q Fe3C Can make it occur at 077wtC 7 67Jhc 727 C cool it slowly 22Wtc below 727 C undercool it T C 1 cu Adapted from Fig 921 Caster 6e Fig 1 40 L 921 adapted from Binary Aoy Phase Diagrams 2nd ed Vol 1 TB 1 20c y Fe3C Massalski EdinChief ASM International aUStemt Materials Park OH 1990 1000 F C OK Eu ctoid 7 e3 ferrltwg uil cooling Ttrans 7277OC le33 VAT 0 quot93C cementite 60 N Undercoolmg by AT Ttrans lt 727 C 40 k quot o I 2 3 4 5 6 9 Fe co wt 0 Chapter 10 3 EUTECTOID TRANSFORMATION RATE AT 0 Growth of pearlite from austenite Diffusive ow Austenite Y cementite Fe 36 of C needed graind ferrite a oun ar y 7 Adapted from p rlite Fig 913 Caster 6e growth direction 0 Reaction rate increases with 3100 U a AT 3 600 C 39 3 AT larger 6 0 C 3 a 75 C g Adapted from of AT smaller g ESTIlgeiib e gt o 100 1 10 102 103 time 3 Chapter 10 4 NUCLEATION AND GROWTH Reaction rate is a result of nucleation and growth of crystals 10 Pearlite Growth regime 50 Nucleation regime 0 t50 Examples pearlite colony W v Nucleation rate increases wl AT Growth rate increases w T Adapted from log time Fig 101 Caster 6e Tjust below TE T moderately below TE T way below TE Nucleation rate low Growth rate high Nucleation rate med Growth rate med Nucleation rate high Growth rate low Chapter 10 5 ISOTHERMAL TRANSFORMATION DIAGRAMS FeC system Co 077wtC Transformation at T 6750 A T675 C Y transformed time s T C E 727 C transformation at 67560 Pearme Adapted from Fig 104 Caiister 6e Fig 104 adapted from H Boyer Ed Atas of Isotherma Transformation and Cooing Transformation Diagrams American Society for Metals 1977 p 369 105time S Chapter106 1 101 1 1 EX COOLING HISTORY FeC SYSTEM Eutectoid composition Co 077wtC Begin atT gt 727C Rapidly cool to 625C and hold isothermally T C Austenite stable TE 727 C 700 Adapted from Fig 1 05 Caiister 6e Fig 105 adapted from H Boyer Ed Atas of isotherma Transformation and Cooing Transformation Diagrams American Society for Metals 1997 p 28 Pearl ite rage 600 1 1o 102 103 104 105 tlmes Chapter 10 7 PEARLITE MORPHOLOGY Two cases Ttransfjust below TE Larger T diffusion is faster Pearlite is coarser 10pm Adapted from Fi 106 a and bCaister 6e Fig 10 from RM Ralls et al An39introduction to Ttransf well below TE Smaller T diffusion is slower Pearlite is finer Materias Science and Engineering p 361 John Wiley and Sons Inc New York 1976 Smaller AT colonies are larger IHIIIQR Larger AT colonies are w smaller Chapter 10 8 NONEQUIL TRANSFORMATION PRODUCTS FeC Bainite quotX lathes strips with long rods of Fesc diffusion controlled F930 Isothermal Transf Diagram cement39te 800 Austenite stable I T C 39E a p I 600 1 007 earlite p egrlitelbainite boundary Hm I Adapted from Fig 108 Caiister 6e Fig 1 00 balmte 108 from Metas Handbook 8th ed 400 Vol 8 Metaiography Structures and A Phase Diagrams American Society for Metals Materials Park OH 1973 200 ol 3 gt0 Bainite reaction rate a 0 co I 7 I 7 o o Q I RT 10 1 10 103 105 rbalmte e time s Adapted from Fig 109Caiister 6e Fig 109 adapted from H Boyer Ed Atas of isotherma Transformation and Chapter 10 9 Cooing Transformation Diagrams American Society for Metals 1997 p 28 OTHER PRODUCTS FeC SYSTEM 1 Spheroidite oc crystals with spherical Fe3C 0L7 diffusion dependent ferrite heat bainite or pearlite for long times reduces interfacial area driving force F93 Isothermal Transf Diagram cemeniho soq Austenite stable 0 T C A quot E p 600 1 00 spheroidite 60 pm SpherOIdlte Adapted from Fig 1010 Caiister 4 o 6e Fig 1010 copyright United B IOOA Sphero39d39te States Steel Corporation 1971 400 A Adapted from FIg 109 Cailster 6e Fig 109 adapted from H Boyer Ed Atas of Isotherma Transformation and Cooing Transformation Diagrams American Society for 200 oz 6 o Metals 1997 p 28 o a 7 101 10 103 105time 3 Chapter 10 10 OTHER PRODUCTS FeC SYSTEM 2 Martensite yFCC to Martensite BCT involves single atom jumps 60 um sites 0 atom sites x Adapted from Fig 1 1011 Caster 6e Isothermal Transf Diagram Austenite Martentite needles T C A E I Austenite Adapted from Fig 1012 Caster 6e Fig 1012 courtesy United States Steel Corporation Fe atom potential OI Ad apted from Fig 1 01 3 Caster 6e y to M transformation is rapid transf depends on T only 5time 3 10 Chapter1011 COOLING EX FeC SYSTEM 1 39 C0 Ceutectoid Rapid Hold Rapid Hold Rapid 0 Three histories cool to for cool to for cool to H HidJ no iiigtim39iiii 350 C 104s Troom casel 250 C 1028 Troom iik kfl ii yi s iiimmiw 800 Austenite stable 0 650 C 208 400 C 10 8 39room P 60 mu S A B 40 o 1 003 6 o Adapted 7 03 lt my from Fig v 0 1015 20 M I A 50 Caster 6e M A 90 i i10 Bamute 101 10 103 105 time 3 Chapter 1012 COOLING EX FeC SYSTEM 2 39 C0 Ceutectoid Rapid Hold Rapid Hold Rapid 0 Three histories cool to for cool to for cool to 350 C 104s Troom H 01 545 W iixwmiimi Case II 250 C 102s Tmom H i Austenite stable 650 C 208 400 C 103S Troom Ad apted from Fig v 1 01 5 50 Caster 6e 30 MA MTItracdof A 10139 1390 13903 39 105times Chapter 10 13 COOLING EX FeC SYSTEM 3 Co Ceutectoid Three histories Case III no Austenite stable 7 100 P50A x S ZN 50P 50A g Rapid Hold Rapid Hold Rapid cool to for cool to for cool to 350 C 104s Troom M Hivltogtltom 250 C 102 Troom 0134 U nxogxxam 650 C 20s 400 C 103s Troom 50P 50B 7 Adapted 0 5 n from Fig 20 M A vnn 1015 M A 12 Caster 6e M A 39 nol 101 1o 1 iv00105 time s 1 500 Chapter 10 14 8 MECHANICAL PROP V SYSTEM 1 Effect Of Wtc 1 1 7 35 quot Pearlite med Pearlite med a lquot 39 7 Cementite ferrite so hard Adapted from Fig 927Caster c lt03977Wtc C0gt3977W1quot C Adapted from Fig 930Caster 6e Fig 927 courtesy Republic 39 6e Fig 930 copyright 1971 by Steel Corporation HyperteCtOId HypereUteCtOId United States Steel Corporation Ll Tswpa Hypo lypcl EL Hypo Hyper3 Y8 MP 1100 80 a 100 339 Adapted from Fig 396 1020 Caster Ga 900 o i FIg 1020 based on rdness 40 g data from Metas 7oo a Handbook Heat L Treating Vol 4 9th 50 2 ed V Masseria 500 f o 3 Managing Ed 8 American Society for 300 E Metals 1981 p 9 r1 HENth 05 C o 05 Is 1 c5 wtC c wtC More wtC TS and Y8 increase EL decreases Chapter 10 15 MECHANICAL PROP FeC SYSTEM 2 Fine vs coarse pearlite vs spheroidite Hypo Hyper 320 g 1Frjggrlite 240 coarse E pearlite f spheroidite 3 160 S a m 80 1 05 wtC Hardness ne gt coarse gt spheroidite AR ne lt coarse lt spheroidite Ductility AR go Hypo Hyper 60 spherondlte 30 coarse pearlite ne 0 1pearI39te 0 05 wtC Adapted from Fig 1021 Caster 6e Fig 1021 based on data from Metas Handbook Heat Treating Vol 4 9th ed V Masseria Managing Ed American Society for Metals 1981 pp 9 and 17 Chapter 10 16 MECHANICAL PROP FeC SYSTEM 3 0 Fine Pearlite vs Martensite Hypo Hyper in 600 martensite 395 E 400 s E1 200 fine pearlite I I1 05 wtC Adapted from Fig 1023 Caster 6e Fig 1023 adapted from Edgar C Bain Functions of the Aoy39ng Eements I39n Stee American Society for Metals 1939 p 36 and RA Grange CR Hribal and LE Porter MetaL Trans A Vol 8A p 1776 Hardness fine pearlite ltlt martensite Chapter 10 17 TEMPERING MARTENSITE reduces brittleness of martensite reduces internal stress caused by quenching TSMPa YSMPa 1800 1 600 Adapted from Fig 1025 Caster 6e Fig 1025 adapted from Fig furnished courtesy of 1 000 Republic Steel Corporation 800 1400 200 400 o Tempering T C 60 V Adapted from V Fig 1024 71 7quot Caster 6e Fig 1024 T a copyright by 7 United States 39 Steel Corporation 1971 0 produces extremely small Fe3C particles surrounded by d 0 decreases TS YS but increases AR Chapter 10 18 M Q a D g q 3 f a 133 in C Austenite y f39x slow mod rate rapid g a coax quench gr quotL gagk Pearlite Bainite Martensite 0 Fe3C layers a 0L Fe3C platesneedles BCT phase proeutectoid phase diffusionless transformation re at 5 5 V 2 Tempered 9 I 2 g MartenSIte a Q at very fine Fe30 particles
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