POSCO Lectures on Bainite

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POSCO Lectures on Bainite

• Microstructure
• Mechanism
• Properties
• Superbainite

Graduate Institute of Ferrous Technology
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Strengthening Mechanisms in Strong Steels
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0.4C 0.2Si 0.7Mn 2Ni 0.25Mo 0.9Cr wt
Honeycombe and Bhadeshia, 1995
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Leslie, 1972
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Leslie, 1972
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Petch, 1959
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Courtesy of Tsuji, Ito, Saito, Minamino, Scripta
Mater. 47 (2002) 893.
Howe, Materials Science and Technology 16 (2000)
1264.
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Interstitial-free steel
Courtesy of Tsuji, Ito, Saito, Minamino, Scripta
Mater. 47 (2002) 893.
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Mixed Microstructures
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Okabayashi and Tomita
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1 µm
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brazing data from Bredzs Case
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Young Bhadeshia
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Young Bhadeshia
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Components of Creep Strength, 2.25Cr1Mo
iron microstructure
550 C
solid solution
600 C
precipitates
Murugananth Bhadeshia, 2001
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elements in solution
Murugananth Bhadeshia, 2001
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Toughness
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cementite forced to inherit the substitutional
solutes in parent
Lord, Bhadeshia, Svensson, 2003
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Kozeschnik Bhadeshia, 2005
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0.4C 2Si 3Mn wt
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Very poor toughness!
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50 µm
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Carbide-free alloys
wt
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kilocycles to Crack Initiation
Yates, Jerath
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Yates, Jerath
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austenite
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0.2C 1.25Si 1.55Mn 0.5Cr 0.15V 0.15Mo wt
15 mm thick plate, without Mo 550C for 5 h
Chang and Bhadeshia
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U.K.
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18 wt Ni
maraging steel
Fracture toughness / MPa vm
QT
Ultimate tensile strength / MPa
Caballero Bhadeshia, 2001
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Size of austenite blocks?
50 µm
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Brittle fibre composite
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Fe-1C-1.5Si wt periodic cracking stress
transfer length
Chatterjee Bhadeshia, 2005
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Ductility
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Caballero, Mateo, Bhadeshia
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Caballero, Mateo, Bhadeshia
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Sherif, 2005, Ph.D. thesis, Cambridge
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Geometrical percolation threshold of overlapping
ellipsoids
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