Bainite Reaction in a Plain Carbon Steel

Aaronson, H.I.; Wells, Cyril

doi:10.1007/bf03377600

Cited by 3 publications

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“…However, grain boundary allotriomorphs are also present. [3,67,68] As previously noted, when nonlamellar, noncooperative carbide formation occurs at grain boundary allotriomorphs, [127] on the generalized microstructural definition, the transformation product is bainite, just as is the product of such carbide precipitation at sideplates and intragranular plates. [2] With decreasing reaction temperature, ferrite plates are increasingly formed as sheaves of parallel plates by means of face-toface sympathetic nucleation.…”

Section: Influence Of X Upon Growth Kinetics Of Ferrite Allotriomorphmentioning

confidence: 99%

Coupled-solute drag effects on ferrite formation in Fe-C-X systems

Aaronson

Reynolds

Purdy

2004

Metall Mater Trans A

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The influence of X upon proeutectoid ferrite/microstructurally defined bainite formation in Fe-C-X alloys, where X is Co, Cr, Cu, Mn, Mo, Ni, Ni, Si, or V, is examined in terms of the competing influences of the coupled-solute drag effect (C-SDE) and the shifting in the paraequilibrium Ae3 curve. The relative strength of the C-SDE was estimated primarily in terms of the influence of X upon the Wagner interaction parameter for C-X interaction in austenite,. Changes in the W s (Widmanstät-ten-start temperature) with X additions at a constant pct C are ascribed almost entirely to shifts in the paraequilibrium Ae3. Influence of X upon the steady-state nucleation rate of ferrite allotriomorphs at austenite grain faces is largely explicable upon the same basis, though additional effects appear to be exerted by Mn and Ni upon relative values of the interfacial energies involved in the nucleation process. Development of a bay in the TTT curve for initiation of ferrite formation occurs more readily with increasingly negative and increasing carbon concentration. When , considerably larger X and C concentrations are required to form what may sometimes be described as a "virtual bay," only the lower portion of which is experimentally detectable. As becomes increasingly negative (but not as much when is increasingly positive), the influence of paraequilibrium Ae3 shifts is much diminished. Widmanstätten sideplate formation is also increasingly suppressed and replaced by grain boundary and twin boundary allotriomorphs at temperatures between the upper nose and the bay of the ferrite-start TTT curve. Changes in carbide precipitation patterns and replacement of (Fe, X) 3 C by alloy carbides directly follow from these alterations in ferrite morphology. When is sufficiently negative, incomplete transformation occurs below the bay temperature. Much higher proportions of X and C are required to produce this effect when . Still more negative values of may be required to develop the degenerate ferrite microstructures below the bay that result from increasing C-SDE restrictions on growth and the consequent frequently repeated sympathetic nucleation. 12 g 12 g Ͼ 1 12 g 12 g 12 g 12 g Ͼ 1 12 g 12 g

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Section: Influence Of X Upon Growth Kinetics Of Ferrite Allotriomorphmentioning

confidence: 99%

Coupled-solute drag effects on ferrite formation in Fe-C-X systems

Aaronson

Reynolds

Purdy

2004

Metall Mater Trans A

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“…His emphasis on continuity of ferrite and (overall reaction kinetics) bainite is in accordw ith the present authors' and related writings. [68,[77][78][79] With the aid of D Mo values obtained from experimentbased data on the carbon content of the untransformed austenite during stasis in Fe-C-Mo alloys, Hillertw as thus able to assess the reductioni nt he bulk carbon concentration neededt op roducei ncompletet ransformation. This achievement represents an important advance in our understanding of the incomplete transformation phenomenon.…”

Section: Hillert and Co-workers' Views On Incomplete Transformation Amentioning

confidence: 99%

The incomplete transformation phenomenon in steel

Aaronson

Reynolds

Purdy

2006

Metall Mater Trans A

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The incomplete transformation (ICT) phenomenon is defined as the temporary cessation of ferrite formation (in the absence of carbide precipitation at a : g boundaries) beforethe fraction of austenite transformed to ferrite predicted by the Lever rule is attained. The ICT phenomenoni sc entral to the ''overall reaction kinetics''definition of bainite but plays lesser roles in the quite different groups of phenomena comprising the ''surface relief'' and ''generalized microstructural''d efinitions. Experimental generalizations that can be madeabout the ICT are briefly noted. Effects of alloying elements, X, upon various aspects of the nucleation and growth of ferrite are listed in order of apparently increasing strength. The ICT is seen to be one of the stronger effects in the latter spectrum. Theories of the ICT are then critically examined. The currently most promising theories involve( 1) the cessation of growthi nduced by the coupled-solute drag effect (C-SDE), accentuated by the overlap of the carbon diffusion fields associated with adjacent ferrite crystals; and (2) the concepts of item (1) plus local alloyinge lement partition between ferrite and austenite (LE-NP), thereby making any further ferrite growth require volume diffusion of Xi na ustenite and thus to take placee xceedingly slowly.D istinguishing betweent hese theories will require use of an Fe-C-X system in which the temperature-carbon concentration paths of the paraequilibrium (PE)A e 3 and of the ''no partition'' boundary are well separated. Although the Fe-C-Mosystem has proved convenient for studying many aspects of the ICT phenomenon, it does not fulfill this specification. Fe-C-Mnalloys do so and should be particularly useful subjects for future investigations of the ICT phenomenon.

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“…11-23. Diagrams for starting time (curve) of the a.istenite to bainite transformation for the various alloys studied (4,5,6,7,8,10,11,12,13,. 14,16,17,20) Effect of quenching rate on the bainite kinetics.…”

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confidence: 99%

Effect of alloying elements in steels on the kinetics of the austenite to bainite transformation

Llopis¹

1975

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The purpose of this study was to investigate the effect of different alloying elements on the bainite reaction kinetics. The primary objective was to perform dilatometric studies on four Fe-OX ternary systems in particular (X = Mo, Ni, Cr, Mn). This technique enables us to obtain the reaction start times for the isothermal decomposition of austenite in the bainite range. The second objective was to extend the investigation to include higher combination systems of these same alloying elements such as Fe-C-Mo-Ni, Fe-C-Ni-Cr, Fe-C-Ni-Cr-Mo in order to determine what their interaction effects are in the bainite transformation. All the alloying elements studied accelerated the austenite decomposition at isothermal temperature treatments just above the Ms giving for the reaction start curve an S-like curve. Of the alloying elements studied Mn, Ni, Cr (in order of effectiveness) shifted the bainite reaction to longer times (increasing the hardenability). Mo, instead, accelerated the bainite reaction. All the alloying elements lowered the temperature range of bainite reaction, further additions, even for mixed addition such as Cr-Nij Mo-Cr Ho-Ni suggested an additive effect in lowering the reaction temperature. However combined additions gave a multiplicative-2effecton the reaction start times for the isothermal decomposii inns of austenite, suggesting strong interaction effects. The rcmib im'd addition Cr-Ni was 6 times more effective than Lhe addition of Nf and Cr alone. Similarly the time for Mo-Ni alloys was five, and for Mo-Cr was four times more effective with respect to hainite hardenability.

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Bainite Reaction in a Plain Carbon Steel

Cited by 3 publications

References 0 publications

Coupled-solute drag effects on ferrite formation in Fe-C-X systems

Coupled-solute drag effects on ferrite formation in Fe-C-X systems

The incomplete transformation phenomenon in steel

Effect of alloying elements in steels on the kinetics of the austenite to bainite transformation

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