Precipitation at interphase boundaries

Aaronson, H.I.; Plichta, M.R.; Franti, G. W.; Russell, K.C.

doi:10.1007/bf02646386

Cited by 108 publications

(28 citation statements)

References 36 publications

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“…Aaronson et al [25] analysed the conditions under which nucleation is feasible at moving disordered interface boundary. The restriction that the migration rate of the g/a p boundary,…”

Section: -The Onset Of Pearlite Transformationmentioning

confidence: 99%

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Kinetics model of isothermal pearlite formation in a 0.4C–1.6Mn steel

2002

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The present article is concerned with a theoretical and experimental study of the growth kinetics of pearlite in a 0.4C-1.6Mn medium carbon steels. Factors controlling the isothermal formation of this microconstituent are explored in this work. In this sense, the transition temperature between local equilibrium (LE) and no partition local equilibrium (NPLE) growth mechanisms is theoretically determined. Moreover, the nucleation of pearlite has been considered as a cementite precipitation process on a moving austenite-ferrite interface. Finally, a theoretical model is presented in this work to calculate the evolution of austenite-to-pearlite transformation with time at a very wide temperature range.Keywords phase transformations, kinetics, steels, forging, structural 1-IntroductionPearlite is probably the most familiar microstructural feature in the whole science of metallography.It was discovered by Sorby over 100 years ago, who assumed it to be a lamellar mixture of ferrite and cementite. Pearlite is a very common constituent of a wide variety of steels, where it provides a substantial contribution to strength, so it is not surprising that this phase has received intense study [1].It is now generally agreed that during pearlite growth the alloying element distributes between the ferrite and cementite at low supersaturations (LE mechanism), and the growth is controlled by alloying element boundary diffusion. At higher supersaturations pearlite growth occurs without any partitioning of the alloying element (NPLE mechanism ) and it is controlled by carbon volume diffusion [2]. The partitioning of alloying elements has been experimentally observed by Razik et al. [3], , and Chance and Ridley [5] in a number of Fe-C-Mn, Fe-C-Si, and Fe-C-Cr alloys. In all these studies, the partitioning was observed at low supersaturations, whereas below a characteristic temperature of the steel no partition was found.Recent works have demonstrated that medium carbon forging steels with acicular ferrite microstructure can be manufactured at industrial scale [6][7][8]. The main interest of this microstructure lies in the good combination of mechanical properties that presents as compared with bainite and especially with ferritic-pearlitic microstructures. In those steels, acicular ferrite is always formed after the growth of allotriomorphic ferrite and pearlite. As a consequence, acicular ferrite transformation is inevitably influenced by previous allotriomorphic ferrite and pearlite formation. The role of the allotriomorphic ferrite to promote the formation of acicular ferrite to the detriment of bainite in a two stages heat treatment has been reported in previous works [9][10].Thus, the amount of acicular ferrite increases as allotriomorphic ferrite is formed along the austenite grain boundaries because saturation of nucleation sites occurs. However, if pearlite transformation follows the allotriomorphic ferrite one, there will not be untransformed austenite to obtain a massive acicular ferrite transformation as temperatu...

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“…Aaronson et al [25] analysed the conditions under which nucleation is feasible at moving disordered interface boundary. The restriction that the migration rate of the g/a p boundary,…”

Section: -The Onset Of Pearlite Transformationmentioning

confidence: 99%

“…In this work, a value of K= 0.0001 has been considered [25]. Likewise, a g has been calculated as reported by Dyson and Holmes considering the dependence of alloying elements on the lattice parameter of austenite [26].…”

Section: Boltzmann Constant; T Is the Isothermal Temperature; D Cmentioning

confidence: 99%

Kinetics model of isothermal pearlite formation in a 0.4C–1.6Mn steel

2002

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“…The process is for the most part associated with a step mechanism of a/c interface motion, the particles precipitating on the stationary, immobile component of the interface 96 because the steps themselves move too rapidly to allow successful nuclei to develop. 99,100 So the idea of interphase precipitation has been around for four decades but, remarkably, it has just seen a new avatar. 101,102 This is in the context of high strength, low alloy steels used in structural applications with a yield strength in the range 400-500 MPa.…”

Section: Guest Editorialmentioning

confidence: 99%

Guest Editorial: Personal perspective on microstructure of steels: 25th anniversary of MST and collection of papers in honour of Sir Robert Honeycombe

Bhadeshia

2010

Materials Science and Technology

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“…For P nodule to form on the surface of growing grain, the velocity of the migrating / interface (# = ) should be low enough to allow the nucleation of cementite () particle. The critical velocity has been analyzed by Aaronson et al 25) In eqs. 9, a is the lattice parameter in , ÁG V is the volume free energy change associated with nucleation given conveniently by eq.…”

Section: Kinetics Of Pearlitementioning

confidence: 99%

Prediction of Bainite Intervened in Ferrite-Pearlite Forging Steel I. Modeling

et al. 2009

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The successive ferrite () + pearlite (P) transformations from austenite () were modeled to predict the presence of bainite in as-forged medium-carbon manganese steels. The kinetics of diffusional transformations were calculated based on classical nucleation and growth theory coupled with CALPHAD multi-component thermodynamics. The description of the growth rate of proeutectoid-includes a time dependence due to the carbon enrichment in the remaining . The / interface was assumed to be in negligible-partitioned local equilibrium (NPLE). The kinetics calculation of P nucleating on the surface was integrated into the model. Given the transformation temperature range in continuous cooling, the growth rate of P was also expressed in the NPLE constraint for /cementite. The concentration of untransformed ( U ) can be monitored and should be dependent on the extent of the preceding transformations. Thus, the energies available for the nucleation and diffusionless growth of bainitic-were evaluated from the thermodynamics of the U single-phase system, which is proposed as a method to predict the inclusion of bainite in the final þ P microstructure.

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Precipitation at interphase boundaries

Cited by 108 publications

References 36 publications

Kinetics model of isothermal pearlite formation in a 0.4C–1.6Mn steel

Kinetics model of isothermal pearlite formation in a 0.4C–1.6Mn steel

Guest Editorial: Personal perspective on microstructure of steels: 25th anniversary of MST and collection of papers in honour of Sir Robert Honeycombe

Prediction of Bainite Intervened in Ferrite-Pearlite Forging Steel I. Modeling

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