19. Phases in iron 910˚C 1390˚C 1535˚C AUSTENITE (gamma) LIQUID FERRITE (delta) FERRITE (alpha) FERRITE Body centred cubic (bcc) AUSTENITE Face centred cubic (fcc)
20. Iron-carbon diagram Percentage Carbon Temperature Liquid Austenite + liquid Austenite Austenite + Fe 3 C Ferrite + Fe 3 C Alpha ferrite Delta ferrite A+F 1535˚C 1390˚C 1130˚C 723˚C 4.3% 0.83% 0.02% 1.7% 910˚C
21. Iron-iron carbide diagram + Fe 3 C + Fe 3 C 910°C 723°C 0.02% 0.83% Temperature Percent Carbon
22.
23. Structure of pearlite Ferrite (0.02% C) Cementite (6.67% C) Pearlite (0.8% C average)
24. Pearlite microstructure Alternate plates of carbide and ferrite. Normally the structure cannot be resolved. Particularly slow cooling has been used. 10 m
25. Iron-iron carbide diagram + Fe 3 C + Fe 3 C A 3 A 1 910°C 723°C 0.02% 0.83% Temperature Percent Carbon Hypoeutectoid Hypereutectoid
36. Isothermal transformation diagram Martensite Upper bainite Lower bainite A + F + P A + B Austenite A + M Time (Seconds) Temperature (Deg C) 1 10 100 1000 M s M f Pearlite (+ ferrite) 100% Ac 1 0%
39. Martensite Martensite is created when austenite transforms by a shear mechanism instead of by nucleation and growth. The shear transformation products are acicular. In this case, because of high carbon (1.2%) there is retained austenite.