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Diagramas de Equilíbrio   e TransformacoesComposicao + Processamento = Microestrutura + Propriedades                      ...
GOL• Esbocar diagramas de fases simples (isomorfos,  euteticos e eutetoides);• Identificar as regioes de fases, linhas liq...
Sumario•   Contextualizacao•   Introducao (aplicacao, limitacao)•   Diagramas de Fases/Equilibrio (X,T,P)•   Conceitos (co...
CONTEXTUALIZAÇÃO• Aplicacao: –   Quimico-Fisica –   Engenharia –   Mineralogia –   Ciencia dos Materiais                  ...
INTRODUÇÃOEXEMPLOS “PRÁTICOS” – Brasagem com ligas Pb-Sn
INTRODUÇÃOEXEMPLOS “PRÁTICOS” - Brasagem de Chips de Si
Diagramas de Fases/EquilibrioMapas para Determinação da MicroestruturaRepresentação gráfica de dados:    informações sobr...
DIAGRAMAS DE EQUILIBRIORepresentacoes graficas dos estados de equilibrio disponivel paraum sistema e a influencia dos esta...
CONCEITOSComponente: elementos quimicos e compostosestoiquiometricos (Al, H2O, Cu, Fe3C) 8                                ...
DIAGRAMA UNARIO                                                                   composicao quimica fixa,                ...
DIAGRAMA UNARIO
ALOTROPIA              composicao              quimica fixa,              T e P variaveis            I - XV: alotropos    ...
ENERGIA LIVRE                 GsolidoG [kJ/mol]                                          G(T,p)= H - T.S                  ...
LEI DAS FASES DE GIBBS                Graus de liberdade (F) de um sistema fechado em equilibrio, em                termos...
Solubility Limit: Water-Sugar                   Solubilidade do Açúcar em Água• Changing T can change # of phases: path A ...
Sistemas Eutéticos Binários  Concept Check 9.5 (SEM solubilidade no estadoO–NaClEx: NaCl-H2O) Below is a portion of the H2...
SOLUBILIDADE SÓLIDA     ELEMENTOS PUROS           Regra Hume-Rothery:           •Razao raio atomico (± 15%)           •Est...
SOLUBILIDADE SÓLIDA      INTERSTICIAIS
DIAGRAMA - experimental                           "#!$%&()*+!,-%!,)&%!./)0!1$&!,-%!23$(%0!.*4!$%56.                       ...
REGRA DA ALAVANCA              R         Co    S    α                                   LWα = S/(R+S) = Co - CL / Cα - CLW...
SISTEMA ISOMORFO Cu-Ni                                                9.7 Binary Isomorphous Systems • 259  Figure 9.3 (a)...
6T_c09_252-310 11/29/05 11:33 Page 265                                                                                    ...
DIAGRAMA BINÁRIO  SOLUÇÃO SÓLIDA TOTAL
MICROESTRUTURAS DE LIGAS     COM SOLUÇÃO SÓLIDA TOTAL
alloys are affected by composition as other structural variables (e.g., grain size) are                                   ...
SISTEMA EUTÉTICO  SEM SOLUÇÃO SÓLIDA
MICROESTRUTURAS DE LIGAS       SEM SOLUÇÃO SÓLIDA
molten at about 185ЊC (365ЊF), which makes this material especially attractive as a                               SISTEMA ...
tion at the point where ww¿ crosses the solidus line. The resulting alloy is poly-  crystalline with a uniform composition...
MICROESTRUTURA MONOFÁSICA
(C3 in Figure 9.13). Consider an alloy having this composition that is cooled from   a temperature within the liquid-phase...
1496T_c09_252-310 1/9/06 13:00 Page 280                                                                                   ...
DIAGRAMA Pb-Sn (liga hipoeutética)
Representação Esquemática                 phase field. To distinguish one a from the other, that which resides in theutect...
apter 9 / Phase Diagrams                     DIAGRAMA Pb-Sngure 9.13 chematic ations of                                   ...
Microestrutura EUTETICA
ENERGIA LIVRE             H = Href + ∫CpdT    S = Sref + ∫CpdlnT                                                          ...
austenite                                                    912ЊC (1674ЊF). This austenite persists to 1394ЊC (2541ЊF), a...
Microestruturas Fe-C                            9.18 The Iron–Iron Carbide (Fe–Fe3C) Phase Diagram • 291e 9.25phs of(90ϫ)t...
Section 9.12 and illustrated in Figure 9.16 for the eutectic system. Consider a com-                                      ...
from grain to grain; some of the pearlite appears dark because the many close      spaced layers are unresolved at the mag...
Representação Esquemática                    Reação Eutetoide               9.19 Development of Microstructure in Iron–Car...
phase field (Figure 9.24) are relatively complex and similar to those described for the eutectic systems in Section 9.12. ...
MICROESTRUTURA EUTETOIDE
2nd REVISE PAGE                                    DIAGRAMA Fe-C298 • Chapter 9 / Phase Diagrams       (liga hipereutetoid...
MICROESTRUTURA of Microstructure in Iron–Carbon A               9.19 Development HIPEREUTETOIDEgure 9.33crograph4 wt% C ha...
REAÇÃO EUTETÓIDE   Sistema Fe-C
REAÇÃO EUTETÓIDE         Sistema Fe-CMEV                     MO
Sistema Ferro-Carbono   Digrama de Equilíbrio
Ferro-Fundido Branco     Sistema Fe-C
Sistema Ferro-Carbono   Digrama de Equilíbrio
Ferro-Fundido Cinzento      Sistema Fe-C
eutectoid reaction but also the relative fra                                    Influencia de outros Elementos            ...
required for the transformation to proceed halfway to completion, t0.5, or                                                ...
CONCEITOSTransformacao de fase: difusiva ou displaciva.Difusiva: solidificacao, alotropicas, recristalizacao,crescimento d...
ters 10 and 11.                                                                                                           ...
2nd REVISE PAGES                                                                                                system has...
REAÇÃO EUTETÓIDE - Perlita8 • Chapter 10 / Phase Transformations in Metals        Sistema Fe-C        Figure 10.15 otomicr...
Diagramas de Equilibrio e Transformações
Diagramas de Equilibrio e Transformações
Diagramas de Equilibrio e Transformações
Diagramas de Equilibrio e Transformações
Diagramas de Equilibrio e Transformações
Diagramas de Equilibrio e Transformações
Diagramas de Equilibrio e Transformações
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Diagramas de Equilibrio e Transformações

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EMC 5719/5712 - Materiais e Microestruturas (/Fundamentos de Engenharia de Materiais 2), prof. Paulo Wendhausen.
Curso de Engenharia de Materiais
Departamento de Engenharia Mecânica
Universidade Federal de Santa Catarina

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  1. 1. Diagramas de Equilíbrio e TransformacoesComposicao + Processamento = Microestrutura + Propriedades EMC5712-Materiais e Microestrutura Prof. Wendhausen Daphiny Pottmaier, posdoc Fonte figuras: Callister 7ed. Agosto & Dezembro 2011.
  2. 2. GOL• Esbocar diagramas de fases simples (isomorfos, euteticos e eutetoides);• Identificar as regioes de fases, linhas liquidus- solvus-solidus e pontos de coexistencia;• Calcular composicoes das fases (linha de amarracao) e fracoes massicas (regra da alavanca);• Localizar as temperaturas e composicoes das transformacoes (pontos/linhas);• Escrever as reacoes para as transformacoes e desenvolvimento das microestruturas.
  3. 3. Sumario• Contextualizacao• Introducao (aplicacao, limitacao)• Diagramas de Fases/Equilibrio (X,T,P)• Conceitos (componente, fase, sistema, solucao)• Unario (H2O)• Isomorfo (Cu-Ni)• Eutetico (Pb-Sn)• Eutetoide (Fe-C)• Conceitos (difusiva/displaciva, cinetica)• Diagramas Tempo-Temperatura-Transformacao
  4. 4. CONTEXTUALIZAÇÃO• Aplicacao: – Quimico-Fisica – Engenharia – Mineralogia – Ciencia dos Materiais • Limitacoes: – Taxa de Transformacao – TTT
  5. 5. INTRODUÇÃOEXEMPLOS “PRÁTICOS” – Brasagem com ligas Pb-Sn
  6. 6. INTRODUÇÃOEXEMPLOS “PRÁTICOS” - Brasagem de Chips de Si
  7. 7. Diagramas de Fases/EquilibrioMapas para Determinação da MicroestruturaRepresentação gráfica de dados:  informações sobre os compostos puros  natureza das interações entre mais de um componenteInformações disponíveis diretamente no diagrama:  Tf de cada componente puro  redução de Tf pela mistura de 2 ou mais componentes  interação de dois componentes (Fe + C) para formar um terceiro (Fe3C )  presença e grau de solubilidade sólida  efeito da temperatura na solubilidade sólida  temperatura de transformação polimórfica  quantidade e composição das fases líquidas e sólidas a temperatura e composição química global específica  presença de líquidos imiscíveis a altas temperaturas
  8. 8. DIAGRAMAS DE EQUILIBRIORepresentacoes graficas dos estados de equilibrio disponivel paraum sistema e a influencia dos estados de equilibrio com acomposicao (X), temperatura (T) e pressao (P). Equilibrio se X, T e p sao estaveis, nao muda com o tempo. Descrito termodinamicamente como o estado do sistema dado pela minima energia livre (G).
  9. 9. CONCEITOSComponente: elementos quimicos e compostosestoiquiometricos (Al, H2O, Cu, Fe3C) 8 ChapterSistema: categorizado pelo numero de componentes unario, binario, ternario, quaternario Chapter 8 Phase DiagramsFase: caracteristicas fisicasae quimicas (solidos), A phase in a material is region that differ in its microstructure andmiscibilidade (liquidos) another region (gases) or composition from e uniforme Phase Diagram Homogeneo x Heterogeneo in a material is a region that differ in its mic A phase or composition from another regionSolucao: solvente e solutoLimite de Solubilidade Al2CuMg Al2CuMg H2O(solid, ice) in H2O Al (liquid) ! 2 phases H2O(so Al • homogeneous in crystal structure and atomic arrangement (liquid • have same chemicalhomogeneous in crystal structure and atomic arra • and physical properties throughout
  10. 10. DIAGRAMA UNARIO composicao quimica fixa, T e P variaveis 100 fusao Liquido congelamento evaporacao H2O 3 fases: solido, condensacao liquido, gas. 1 SolidoPressao [atm] Ponto triplo: sublimacao Gas 0.0098 °C, deposicao 0.0063 atm. 0 100 Regiao: 1 fase Temperatura [°C] Linha: 2 fases SI: Kelvin, Pascal Ponto: 3 fases
  11. 11. DIAGRAMA UNARIO
  12. 12. ALOTROPIA composicao quimica fixa, T e P variaveis I - XV: alotropos do gelo. H2O
  13. 13. ENERGIA LIVRE GsolidoG [kJ/mol] G(T,p)= H - T.S H = Href + ∫CpdT Gliquido S = Sref + ∫CpdlnT Ggas H2O 0 100 Temperatura [°C] P=1 atm
  14. 14. LEI DAS FASES DE GIBBS Graus de liberdade (F) de um sistema fechado em equilibrio, em termos de fases separadas (P) e componentes quimicos (C) e variaveis do processo (N). 100 Liquido F+P=C+N (i) H2O, C = 1 (ii) 1 Solido (iii) (i) P = 1, F = 2 (ii) P = 2, F = 1Pressao [atm] Gas (iii) P = 3, F = 0 0 100 Temperatura [°C] F: freedom, P: phase
  15. 15. Solubility Limit: Water-Sugar Solubilidade do Açúcar em Água• Changing T can change # of phases: path A to B.• Changing Co can change # of phases: path B to D B (100,70) D(100,90) 1 phase 2 phases 10 0 80 L (liquid)Temperature (°C) 60 + L S (liquid solution (solid 40 i.e., syrup) sugar) 20 A(70, 20 ) T : B-D 2 phases C : B-A 0 0 20 40 60 70 80 10 0 C o =Composition (wt% sugar) Adapted from Callister Chapter 8
  16. 16. Sistemas Eutéticos Binários Concept Check 9.5 (SEM solubilidade no estadoO–NaClEx: NaCl-H2O) Below is a portion of the H2 sólido phase diagram: 10 50 Liquid (brine) 40 0 30 Salt Temperature (°C) Temperature (°C) ϩ Ice 20 Liquid ϩ (brine) Ϫ10 Liquid (brine) 10 0 Ϫ20 Ϫ10 Ice ϩ Salt Ϫ20 Ϫ30 NaCl 0 10 20 30 H2O 100 90 80 70 Composition (wt%)
  17. 17. SOLUBILIDADE SÓLIDA ELEMENTOS PUROS Regra Hume-Rothery: •Razao raio atomico (± 15%) •Estrutura cristalina •Eletronegatividade (± 0.4 e.u.) •Mesma Valencia
  18. 18. SOLUBILIDADE SÓLIDA INTERSTICIAIS
  19. 19. DIAGRAMA - experimental "#!$%&()*+!,-%!,)&%!./)0!1$&!,-%!23$(%0!.*4!$%56. 23$(%0!)*4)2.,%!,-%!,%&5%$.,3$%0!1!,-%!06)430!.*4!6 .6670!,-%!06)430!.*4!6)93)430!,!<%!56,,%4!,!5$43 ! !)&%!./)0!1$&!,-%!23$(%0!.*4!$%56.2)*+!),!7),-!2&50),)*8!,-%!26)*+!%!,%&5%$.,3$%0!1!,-%!06)430!.*4!6)93)430!1$!.!+)(%*!2&50),)*:!;-)0!!.*4!6)93)430!,!<%!56,,%4!,!5$432%!,-%!5-.0%!4).+$.&=! !-%!,)&%!./)0!1$&!,-%!23$(%0!.*4!$%56.2)*+!),!7),-!2&50),)*8!,-%!26)*+! ! !,-%!,%&5%$.,3$%0!1!,-%!06)430!.*4!6)93)430!1$!.!+)(%*!2&50),)*:!;-)0!430!.*4!6)93)430!,!<%!56,,%4!,!5$432%!,-%!5-.0%!4).+$.&=! !"#$%&#&(&)#)*&# >1!.*!.66#!2*0)0,0!1!&$%!,-.*!*%!5-.0%8!,-%!.& 13*4!<#!.556#)*+!,-%!6%(%$!$36%!,!,-%!5-.0%!4).+$.& ! ;-%!6%(%$!$36%!2.*!<%!%/56.)*%4!<#!2*0)4%$)*+!.!0)& .66#!)0!$%5$%0%*,%4!<#!,-%!1362$3&!.*4!,-%!2&50) .!<.$:!;-%!5$5$,)*0!1!,-%!5-.0%0!5$%0%*,!.$%!4%,% <.6.*2%!,-%!0#0,%&:! ! ! !
  20. 20. REGRA DA ALAVANCA R Co S α LWα = S/(R+S) = Co - CL / Cα - CLWL = R/(R+S) = Cα - Co / Cα - CL
  21. 21. SISTEMA ISOMORFO Cu-Ni 9.7 Binary Isomorphous Systems • 259 Figure 9.3 (a) The Composition (at% Ni) copper–nickel phase 0 20 40 60 80 100 diagram. (b) A 1600 portion of the copper–nickel phase 2800 diagram for which 1500 compositions and phase amounts are Liquid 1453°C determined at point 2600 B. (Adapted from 1400 Phase Diagrams of Temperature (°C) Temperature (°F)Binary Nickel Alloys, Solidus lineP. Nash, Editor, 1991. Liquidus line 2400 1300 ␣ +L Reprinted by permission of ASM B International,Materials Park, OH.) 1200 ␣ 2200 1100 A 2000 1085°C 1000 0 20 40 60 80 100 (Cu) Composition (wt% Ni) (Ni) (a)
  22. 22. 6T_c09_252-310 11/29/05 11:33 Page 265 REVISED PAGES DIAGRAMA Cu-Ni Composição9.9 Development das Fases -Isomorphous Alloys • 265 Química of Microstructure in Equilíbrio Figure 9.4 Schematic L representation of the L L development of (35 Ni) (35 Ni) microstructure ␣ (46 Ni) during the 1300 a ␣ equilibrium + L solidification of a 35 wt% Ni–65 wt% Cu alloy. L (32 Ni) b ␣ (46 Ni) c Temperature (°C) ␣ (43 Ni) ␣ (43 Ni) L (24 Ni) d ␣ ␣ L (32 Ni) ␣ ␣ 1200 ␣ e L (24 Ni) ␣ ␣ ␣ ␣ (35 Ni) ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ (35 Ni) ␣ 1100 20 30 40 50 Composition (wt% Ni)
  23. 23. DIAGRAMA BINÁRIO SOLUÇÃO SÓLIDA TOTAL
  24. 24. MICROESTRUTURAS DE LIGAS COM SOLUÇÃO SÓLIDA TOTAL
  25. 25. alloys are affected by composition as other structural variables (e.g., grain size) are Sistemas Isomorfos held constant. For all temperatures and compositions below the melting tempera- ture of the lowest-melting component, only a single solid phase will exist. There- fore, each component will experience solid-solution strengthening (Section 7.9), or (Propriedades Mecânicas) an increase in strength and hardness by additions of the other component. This effect is demonstrated in Figure 9.6a as tensile strength versus composition for the 60 Elongation (% in 50 mm [2 in.]) 60 400Tensile strength (MPa) 50 Tensile strength (ksi) 50 40 300 40 30 200 30 20 0 20 40 60 80 100 0 20 40 60 80 100 (Cu) (Ni) (Cu) (Ni) Composition (wt% Ni) Composition (wt% Ni) (a) (b) Figure 9.6 For the copper–nickel system, (a) tensile strength versus composition, and (b) ductility (%EL) versus composition at room temperature. A solid solution exists over all compositions for this system.
  26. 26. SISTEMA EUTÉTICO SEM SOLUÇÃO SÓLIDA
  27. 27. MICROESTRUTURAS DE LIGAS SEM SOLUÇÃO SÓLIDA
  28. 28. molten at about 185ЊC (365ЊF), which makes this material especially attractive as a SISTEMA EUTETICO Pb-Sn low-temperature solder, since it is easily melted. Composition (at% Sn) 0 20 40 60 80 100 327°C 600 300 Liquid 500 232°C ␣ +LTemperature (°C) Temperature (°F) 200 ␣ ␤ +L 400 183°C ␤ 18.3 61.9 97.8 300 100 ␣ + ␤ 200 100 0 0 20 40 60 80 100 (Pb) Composition (wt% Sn) (Sn)
  29. 29. tion at the point where ww¿ crosses the solidus line. The resulting alloy is poly- crystalline with a uniform composition of C1, and no subsequent changes will occur DIAGRAMA Pb-Sn 400 Figure 9.11 Schematic L representations of the w (C1 wt% Sn) equilibrium microstructures for ␣ a lead–tin alloy of composition a L b L C1 as it is cooled from the liquid-phase region. 300 Liquidus c ␣ ␣ ␣ +LTemperature (°C) ␣ ␣ Solidus 200 (C1 wt% Sn) ␣ 100 ␣ +␤ wЈ 0 10 20 30 C1 Composition (wt% Sn)
  30. 30. MICROESTRUTURA MONOFÁSICA
  31. 31. (C3 in Figure 9.13). Consider an alloy having this composition that is cooled from a temperature within the liquid-phase region (e.g., 250ЊC) down the vertical line yy¿SISTEMA EUTETICO Pb-Sn Figure 9.12 Schematic representations of the x equilibrium microstructures L d L for a lead–tin alloy of (C2 wt% Sn) composition C2 as it is cooled from the liquid-phase region. 300 L ␣ e ␣ ␣ ␣ +L Temperature (°C) ␣ 200 ␣ ␣ C2 wt% Sn f ␤ Solvus line g ␣ 100 ␣ +␤ xЈ 0 10 20 30 40 50 C2 Composition (wt% Sn)
  32. 32. 1496T_c09_252-310 1/9/06 13:00 Page 280 2nd REVISE PAG DIAGRAMA Pb-Sn 280 • Chapter 9 / Phase Diagrams (liga hipoeutética) L (C4 wt% Sn) z j ␣ 600 300 L ␣ +L L 500 ␣ (18.3 wt% Sn) k Temperature (°C) Temperature (°F) 200 400 ␤ +L ␣ l ␤ m L (61.9 wt% Sn) Eutectic structure 300 Primary ␣ ␣ + ␤ (18.3 wt% Sn) 100 200 ␤ (97.8 wt% Sn) Eutectic ␣ (18.3 wt% Sn) 100 zЈ 0 0 20 60 80 100 (Pb) C4 (Sn) (40) Composition (wt% Sn) Figure 9.16 Schematic representations of the equilibrium microstructures for a lead–tin
  33. 33. DIAGRAMA Pb-Sn (liga hipoeutética)
  34. 34. Representação Esquemática phase field. To distinguish one a from the other, that which resides in theutectic phase structure is called eutectic a, while the other that formed prior to cro eutectic isotherm is termed primary a; both are labeled in Figureprimary phase Reação Eutética photomicrograph in Figure 9.17 is of a lead–tin alloy in which both prim eutectic structures are shown. Figure 9.15 Schematic represen the formation of the eutectic str ␤ Pb the lead–tin system. Directions o of tin and lead atoms are indicat blue and red arrows, respectively ␣ Sn Liquid ␤ Pb ␣ Sn Eutectic growth direction ␤ Pb
  35. 35. apter 9 / Phase Diagrams DIAGRAMA Pb-Sngure 9.13 chematic ations of 600 300 y Luilibrium (61.9 wt% res for a Sn)n alloy of L 500 hmposition ␣ +Lnd below Temperature (°C) Temperature (°F) eutectic 200 ␣ 183°C ␤+L ␤ 400perature. 18.3 i 97.8 300 100 ␣+␤ 200 ␣ (18.3 wt% ␤ (97.8 wt% Sn) Sn) 100 yЈ 0 0 20 40 60 80 100 (Pb) C3 (Sn) (61.9) Composition (wt%Sn)
  36. 36. Microestrutura EUTETICA
  37. 37. ENERGIA LIVRE H = Href + ∫CpdT S = Sref + ∫CpdlnT γ 1400˚ G(T,p)= H - T.S Fe3CG [kJ/mol] L G Gccc Gliquido Eutetico 1147˚ Gcfc γ L Fe3C G Fe L T γ 912 1394 1538 γ + Fe3C α α + Fe3C Temperatura [°C] P=1 atm Fe C % Eutetico
  38. 38. austenite 912ЊC (1674ЊF). This austenite persists to 1394ЊC (2541ЊF), at which tem SISTEMA EUTETOIDE Fe-C the FCC austenite reverts back to a BCC phase known as d ferrite, whic Composition (at% C) 0 5 10 15 20 25 1600 1538°C 1493°C ␦ L 1400 2500 1394°C ␥+L 1200 1147°CTemperature (°C) Temperature (°F) 2.14 4.30 ␥, Austenite 2000 1000 912°C ␥ + Fe3C 800 ␣ 1500 + 727°C ␥ 0.76 0.022 600 ␣ + Fe3C ␣, Ferrite Cementite (Fe3C) 1000 400 0 1 2 3 4 5 6 6.70 (Fe) Composition (wt% C)
  39. 39. Microestruturas Fe-C 9.18 The Iron–Iron Carbide (Fe–Fe3C) Phase Diagram • 291e 9.25phs of(90ϫ)teniteyright nited Steel tion.) (a) (b) Microestrutura Ferrita α Microestrutura Austenita melts at 1538ЊC (2800ЊF). All these changes are apparent along the left vertical axis 1
  40. 40. Section 9.12 and illustrated in Figure 9.16 for the eutectic system. Consider a com- DIAGRAMA Fe-C position C0 to the left of the eutectoid, between 0.022 and 0.76 wt% C; this is termedhypoeutectoid alloy a hypoeutectoid (less than eutectoid) alloy. Cooling an alloy of this composition is represented by moving down the vertical line yy¿ in Figure 9.29. At about 875ЊC , (liga hipoeutetoide) point c, the microstructure will consist entirely of grains of the g phase, as shown 1100 Figure 9.29 Schematic ␥ representations of the ␥ microstructures for an ␥ ␥ iron–carbon alloy of 1000 ␥ hypoeutectoid composition C0 ␥ + Fe3C (containing less than 0.76 wt% y ␥ M ␥ C) as it is cooled from within 900 the austenite phase region to ␥ ␣ c ␥ below the eutectoid temperature. Temperature (°C) ␥ 800 ␥ d ␥ ␥ e Te N f O 700 ␣ Pearlite 600 Fe3C Proeutectoid ␣ Eutectoid ␣ 500 ␣ + Fe3C yЈ 400 0 1.0 2.0 C0 Composition (wt% C)
  41. 41. from grain to grain; some of the pearlite appears dark because the many close spaced layers are unresolved at the magnification of the photomicrograph. The MICROESTRUTURA HIPOEUTETOIDE 0 hC a e e d Proeutectoidϫ. ferrite h c .) Pearlite
  42. 42. Representação Esquemática Reação Eutetoide 9.19 Development of Microstructure in Iron–Carbo Austenite grain Figure 9.28 boundary representatio formation of austenite; dir ␣ diffusion ind Ferrite (␣) Austenite (␥ ) Austenite Ferrite (␣) (␥ ) Ferrite (␣)Cementite Growth direction (Fe3C) Ferrite (␣) of pearlite ␣ Carbon diffusion
  43. 43. phase field (Figure 9.24) are relatively complex and similar to those described for the eutectic systems in Section 9.12. Consider, for example, an alloy of eutectoid DIAGRAMA Fe-C composition (0.76 wt% C) as it is cooled from a temperature within the g phase re- gion, say, 800ЊC—that is, beginning at point a in Figure 9.26 and moving down the 1100 Figure 9.26 Schematic representations of the microstructures for an iron–carbon alloy of eutectoid 1000 ␥ ␥ + Fe3C composition (0.76 wt% C) above and below the eutectoid temperature. 900 x ␥ ␥Temperature (°C) ␥ 800 a ␥ ␣ +␥ 727°C b ␣ 700 ␣ 600 Fe3C 500 ␣ + Fe3C xЈ 400 0 1.0 2.0 Composition (wt% C)
  44. 44. MICROESTRUTURA EUTETOIDE
  45. 45. 2nd REVISE PAGE DIAGRAMA Fe-C298 • Chapter 9 / Phase Diagrams (liga hipereutetoide) 1100 P Figure 9.32 Schematic representations of the ␥ + Fe3C microstructures for an iron–carbon alloy of 1000 ␥ z hypereutectoid composition ␥ ␥ C1 (containing between 0.76 ␥ g and 2.14 wt% C), as it is ␥ 900 cooled from within the Fe3C austenite phase region to ␥ below the eutectoid ␥ temperature. Temperature (°C) 800 ␥ h ␥ ␣ +␥ O i 700 ␣ Pearlite 600 ␣ Proeutectoid Fe3C Eutectoid Fe3C 500 ␣ + Fe3C z 400 0 1.0 2.0 C1 Composition (wt% C)
  46. 46. MICROESTRUTURA of Microstructure in Iron–Carbon A 9.19 Development HIPEREUTETOIDEgure 9.33crograph4 wt% C having astructure f a whiteeutectoid networknding the Proeutectoid cementite colonies. opyrighty United tes Steel oration.) Pearlite
  47. 47. REAÇÃO EUTETÓIDE Sistema Fe-C
  48. 48. REAÇÃO EUTETÓIDE Sistema Fe-CMEV MO
  49. 49. Sistema Ferro-Carbono Digrama de Equilíbrio
  50. 50. Ferro-Fundido Branco Sistema Fe-C
  51. 51. Sistema Ferro-Carbono Digrama de Equilíbrio
  52. 52. Ferro-Fundido Cinzento Sistema Fe-C
  53. 53. eutectoid reaction but also the relative fra Influencia de outros Elementos phase that form. Steels are normally alloy either to improve their corrosion resistan treatment (see Section 11.8). 9.20 The Influence of Other Alloying Elements • 301 Figure 9.34 The dependence of Figu Ti 2400 0.8 eutectoid temperature on alloy com Mo W Ni 1200 2200 concentration for several alloying forEutectoid temperature (°C) Eutectoid temperature (°F) Eutectoid composition (wt% C) Si elements in steel. (From Edgar C. Edg 2000 0.6 Bain, Functions of the Alloying Elem 1000 American Society 1939 Elements in Steel,Cr 1800 Cr 1600 0.4 for Metals, 1939, p. 127.) 800 Si 1400 Mo Mn 0.2 W Mn 1200 Ti 600 Ni 1000 0 0 2 4 6 8 10 12 14 0 2 4 6 8 10 12 14 Concentration of alloying elements (wt%) Concentration of alloying elements (wt%) Temperatura Eutetoide Composicao Eutetoide existence at room temperature of nonequilibrium phases that do not appear on the
  54. 54. required for the transformation to proceed halfway to completion, t0.5, or Transformation rate—reciprocal of 1 rate ϭ (10.18) the halfway-to- t0.5 TEMPO-TEMPERATURA-TRANSFORMAÇÃO completion transformation time Temperature will have a profound influence on the kinetics and thus on the10_311-357 11/30/05 7:37 Page 323 rate of a transformation. This is PAGES REVISED demonstrated in Figure 10.11, where y-versus-log t 100:37 Page 323 termodinamicamente REVISED PAGES Percent recrystallized 80 como o estado do sistema The Kinetics of Phase Transformations • 323 10.3 60 135ЊC 119ЊC 113ЊC 102ЊC 88ЊC 43ЊC dado pela minima energia 1.0 Figure 10.10 Plot of fraction reacted versus the logarithm of 40 time typical of many solid-state 20 livre (G). Fraction of transformation, y transformations in which temperature is held constant. 0 2 104 10.3 The Kinetics of Phase Transformations • 323 1 10 10 Time (min) 0.5 (Logarithmic scale) 1.0 Figure 10.11 Percent recrystallization as a function of time and at constant Figure 10.10 Plot of fraction temperature for pure copper. (Reprinted with permission from Metallurgical Representacoes graficas dos t0.5 reacted versus the logarithm of Transactions, Vol. 188, 1950, a publication of The Metallurgical Society of AIME, time typical of many solid-state Warrendale, PA. Adapted from B. F. Decker and D. Harker, “Recrystallization in Rolled Fraction of transformation, y 0 Nucleation estados da CINETICA de Growth transformations in which Copper,” Trans. AIME, 188, 1950, p. 888.) temperature is held constant. transformacao para um sistema Logarithm of heating time, t formed material versus the logarithm of time; an S-shaped emsimilar to that in do tempo (t). curve funcao 0.5 of which is distinctive of the new phase. Data are plotted as the fraction of trans- Figure 10.10 represents the typical kinetic behavior for most solid-state reactions. Nucleation and growth stages are also indicated in the figure. For solid-state transformations displaying the kinetic behavior in Figure 10.10, the fraction of transformation y is a function of time t as follows: t0.5 y ϭ 1 Ϫ exp1Ϫkt 2 Avrami equation— n dependence of (10.17) fraction 0 of transformation where k and n are time-independent constants for the particular reaction. The above on time Nucleation expression is often Growth to as the Avrami equation. referred By convention, the rate of a transformation is taken as the reciprocal of time required for the of heating time, tproceed halfway to completion, t0.5, or Logarithm transformation to Transformation rate—reciprocal of 1 rate ϭ (10.18)
  55. 55. CONCEITOSTransformacao de fase: difusiva ou displaciva.Difusiva: solidificacao, alotropicas, recristalizacao,crescimento de grao, etc.Ponto de vista microestrutural: Nucleacao: Homogenea x Heterogenea Crescimento:Displaciva/martensitica: sem difusao, metaestavel.Cinetica: velocidade (tempo) - mecanismo.
  56. 56. ters 10 and 11. system has been chosen because it is familiar and because a wide variety crostructures and mechanical properties are possible for iron–carbon (or steel) 9.18 THE IRON–IRON CARBIDE (Fe–Fe3C) Diagrama TTT Fe-C eutetoide PHASE DIAGRAM 10.5 ISOTHERMAL TRANSFORMATION DIAGRAMS diagram is presented in Figure A portion of the iron–carbon phase Pearlite upon heating, experiences two changes in crystal structure before it ferrite temperature the stable form, called ferrite, or a iron, has a BCC cter 10 / Phase Transformations in Metals Consider again the austenite iron–iron carbide eutectoid reaction Ferrite experiences a polymorphic transformation to FCC austeni 912ЊC (1674ЊF). This austenite persists to 1394ЊC (2541ЊF), at whi Eutectoid reaction the FCC austenite reverts back to a BCC phase known as d ferrit cooling for the iron-iron 100 carbide system Figure 10.13 ∆ a10.022 wt% C2 ϩ Fe3C16.70 wt% C2 (1 g10.76 wt% C2 heating transformed to pearlite Demonstration of how Composition (at% C) Percent of austenite Transformation Transformation which is fundamental to the development of microstructure in steel alloys. an isothermal 5 0 10 15 20 25 temperature 675°C ends 1600 cooling, austenite, having an intermediate carbon concentration, transforms to 1538°C 50 transformation diagram1493°C rite phase, having a much lower carbon content, and also cementite, with a (bottom)␦ is generated L higher carbon concentration. Pearlite is one microstructural product of this 1400 2500 Transformation from percentage ␥ + L formation (Figure1394°C and the mechanism of pearlite formation was disc 9.27), begins previously (Section 9.19) and demonstrated in Figure 9.28. transformation-versus- 1147°C 1200 Temperature plays an important role in the rate of the austenite-to-pe 0 logarithm Austenite ␥, of time 105 transformation. The temperature dependence for an iron–carbon alloy of2000 eute Temperature (°C) 2.14 4.30 1 10 102 103 104 measurements (top). composition is indicated in Figure 10.12, which plots S-shaped curves of the 1000 Time (s) centage transformation versus the logarithm of time at three different tempera [Adapted from H. 912°C ␥ + Fe C 3 For each curve, data were collected after rapidly cooling a specimen compos Boyer, ␣ 800 (Editor), Atlas 100% austenite to the temperature indicated; that temperature was maintained + 1500 727°C of Isothermal ␥ stant throughout the course of the reaction. 0.76 1400 A more convenient way of representing both the time and temperatur Austenite (stable) Eutectoid temperature Transformation and 0.022 pendence of600 transformation is in the+ bottom portion of Figure 10.13. Her this ␣, Ferrite ␣ Fe C 3 Austenite Cooling Transformation vertical and horizontal axes are, respectively, temperature and the logarithm of Cementite (Fe C) 1000 3 700 (unstable) Diagrams, American Two solid curves are plotted; one represents the time required at each temper 400 initiation for Metals,21977, 3 0 1 4 1200 the Society or start of the transformation; C) other is for the transform for (Fe) Composition (wt% the 5 6 6.70 Pearlite conclusion. The dashed curve 9.24 The iron–iron carbide phase transformation compl Figure corresponds to 50% of diagram. [Adapted from Binary Temperature (°C) Temperature (°F) p. 369.] These curves were generated from a series of T. B. Massalski (Editor-in-Chief), 1990. Repr Diagrams, 2nd edition, Vol. 1, plots of the percentage transfo 600 permission of ASM International, Materials Park, OH.] tion versus the logarithm of time taken over a range of temperatures. The S-sh 50% Completion curve curve [for 675ЊC (1247ЊF)], in the upper portion of Figure 10.13, illustrates ho 1000 data transfer is made. In interpreting this diagram, note first that the eutectoid temperature [ 500 Completion curve (~100% pearlite) (1341ЊF)] is indicated by a horizontal line; at temperatures above the eutecto Begin curve 800 100 0 Figure 10.12 For (~ 0% pearlite) iron–carbon alloy 400 eutectoid composi (0.76 wt% C), isothermal fractio cent austenite 102 103 104 105 rcent pearlite 1 10 reacted versus the Time (s) 50 600°C 650°C 675°C 50 logarithm of time the austenite-to-p
  57. 57. 2nd REVISE PAGES system has been chosen because it is familiar and because a wide variety crostructures and mechanical properties are possible for iron–carbon (or steel) Diagrama TTT Fe-C (perlita) 10.5 ISOTHERMAL TRANSFORMATION DIAGRAMS Pearlite Consider again the iron–iron carbide eutectoid reaction Eutectoid reaction 10.5 Isothermal Transformation Diagrams a10.022327C2 ϩ Fe3C16.70 wt% C2 for the iron-iron g10.76 wt% C2 ∆ • wt% cooling (1 carbide system heating 1s 1 min which is fundamental to the development of microstructure in steel alloys. 1h 1 day cooling, austenite, having an intermediate carbon concentration, transforms to rite phase, having a much lower carbon content, and also cementite, with a Eutectoid 1400 A ␥ Austenite (stable) higher carbon concentration. Pearlite is one microstructural product of this temperature 727°C formation (Figure 9.27), and the mechanism of pearlite formation was disc previously (Section 9.19) and demonstrated in Figure 9.28. Temperature plays an important role in the rate of the austenite-to-pe 700 ␥ ␥ ␥ ␥ transformation. The temperature dependence for an iron–carbon alloy of eute composition is indicated in Figure 10.12, which plots S-shaped curves of the ␥ ␥ ␣ Ferrite transformation versus the logarithm of time at three different tempera centage Coarse pearlite For each curve, data were collected after rapidly cooling a specimen compos 100% austenite to the temperature indicated; that temperature was maintained 1200 C stant throughout the course of the reaction.Temperature (°C) Temperature (°F) A more convenient way of representing both the time and temperatur B D pendence of this transformation is in the bottom portion of Figure 10.13. Her 600 Fe3C vertical and horizontal axes are, respectively, temperature and the logarithm of Two solid curves are plotted; one represents the time required at each temper for the initiation or start of the transformation; the other is for the transform Fine pearlite conclusion. The dashed curve corresponds to 50% of transformation compl These curves were generated from a series of plots of the percentage transfo tion versus the logarithm of time taken over a range of temperatures. The S-sh 1000 curve [for 675ЊC (1247ЊF)], in the upper portion of Figure 10.13, illustrates ho data transfer is made. Austenite → pearlite 500 transformation Denotes thatinterpreting this diagram, note first that the eutectoid temperature [ In a transformation (1341ЊF)] is indicated by a horizontal line; at temperatures above the eutecto is occurring 100 0 Figure 10.12 For iron–carbon alloy 800 eutectoid composi (0.76 wt% C), 1 10 102 103 104 105 isothermal fractio cent austenite rcent pearlite reacted versus the Time (s) 50 600°C 650°C 675°C 50 logarithm of time the austenite-to-p
  58. 58. REAÇÃO EUTETÓIDE - Perlita8 • Chapter 10 / Phase Transformations in Metals Sistema Fe-C Figure 10.15 otomicrographs of (a) coarse pearlite d (b) fine pearlite. 00ϫ. (From K. M. Ralls et al., An Introduction to terials Science andEngineering, p. 361. pyright © 1976 by ohn Wiley & Sons, w York. Reprinted by permission of ohn Wiley & Sons, Inc.) Perlita Grosseira Perlita Fina For iron–carbon alloys of other compositions, a proeutectoid phase (either ferrite or cementite) will coexist with pearlite, as discussed in Section 9.19. Thus additional curves corresponding to a proeutectoid transformation also must be in-
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