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made by Rudenok Aleksandra group 832-ams

Material Scientific Department. Tempering of Bainite. made by Rudenok Aleksandra group 832-ams. Scientific Supervisor Ph.D. O. Uzlov Language Supervisor K. Kuznezova. Dnipropetrovsk 2011. Two stages of tempering:.

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made by Rudenok Aleksandra group 832-ams

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  1. Material Scientific Department Tempering of Bainite made by Rudenok Aleksandra group 832-ams Scientific Supervisor Ph.D. O. Uzlov Language Supervisor K. Kuznezova Dnipropetrovsk 2011

  2. Two stages of tempering: • segregation of carbon to defects or forms clusters; • carbides convert into more stable cementite; Fig.1 The time scales associated with a variety of tempering phenomena for bainite. Bainite in Steels. Second Edition. H.K.D.H. Bhadeshia, 2001. 2

  3. Retained austenite Fig.2 The effect of tempering a mixture of bainitic ferrite and retained austenite, х10000. Stark et. al., 1990. 3

  4. Fig.3 Cementite enrichment in a fully bainitic microstructure and one which is a mixture of allotriomorphic ferrite and bainite. Thomson and Bhadeshia, 1994. 4

  5. Sequence of Alloy Carbide Precipitation Fig.4 Equilibrium fractions of carbides at 565°C(838K). After Nutting, 1998. 5

  6. Fig.5 The predicted evolution of precipitate volume fractions at 600°C for three materials: (a) 2Cr1Mo (b) 3Cr1.5Mo and (c) 10CrMoV. Robson and Bhadeshia, 1997. 6

  7. Conclusions: There are important differences in the tempering behaviour of bainite and martensite, because the former autotempers during transformation. Much of the carbon precipitates or partitions from the ferrite during the bainite reaction. The decrease in strength on tempering bainite is smaller because unlike martensite, there is hardly any carbon in solid solution. Major changes in strength occur only when the microstructure coarsens or with the onset of recrystallisation where equiaxed grains of ferrite replace the bainite plates. Minor changes in strength are due to cementite particle coarsening and a general recovery of the dislocation substructure. 7

  8. Thank you for attention! 8

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