Austenite grain growth simulation considering the solute-drag effect and pinning effect

Fujiyama, Naoto; Nishibata, Toshinobu; Seki, Akira; Hirata, Hiroyuki; Kojima, Kazuhiro; Ogawa, Kōichi

doi:10.1080/14686996.2016.1244473

Cited by 28 publications

(8 citation statements)

References 32 publications

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“…Thus, during the austenitization heat treatment at 920 • C, the austenite grains that have nucleated and grown in Si, Mn, and Cr-rich zones (last austenite to be formed) are smaller due to the smaller ∆T. (3) A factor that may be favoring a bi-modal distribution is the so-called solute drag effect [47][48][49]. It is well-known that solute atoms (impurities or alloying elements) segregated to the austenite grain boundaries can reduce their mobility and exert a drag force that retards the kinetics.…”

Section: Determination Of the Ms Temperature And The Prior Austenitic Grain Sizementioning

confidence: 99%

Effect of Microsegregation and Bainitic Reaction Temperature on the Microstructure and Mechanical Properties of a High-Carbon and High-Silicon Cast Steel

Basso

Eres-Castellanos

Tenaglia

et al. 2021

Metals

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Bainitic microstructures obtained in high-carbon (HC) and high-silicon (HSi) steels are currently of great interest. Microstructural evolution and the bainitic transformation kinetics of a high-carbon and high-silicon cast steel held at 280, 330, and 380 °C was analyzed using dilatometry, X-ray diffraction, optical and scanning electron microscopy, and electron backscatter diffraction (EBSD). It is shown that the heterogeneous distribution of silicon (Si), manganese (Mn), and chromium (Cr) associated to microsegregation during casting has a great impact on the final microstructure. The transformation starts in the dendritic zones where there is a lower Mn concentration and then expands to the interdendritic ones. As Mn reduces the carbon activity, the interdendritic areas with a higher Mn concentration are enriched with carbon (C), and thus, these zones contain a greater amount of retained austenite plus martensite, resulting in a heterogeneous microstructure. Higher transformation temperatures promote higher amounts of residual austenite with poor thermal/mechanical stability and the presence of martensite in the final microstructure, which has a detrimental effect on the mechanical properties. Tensile tests revealed that the ultra-fine microstructure developed by the transformation at 280 °C promotes very high values of both tensile and yield stress (≈1.8 GPa and 1.6 GPa, respectively), but limited ductility (≈2%).

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Section: Determination Of the Ms Temperature And The Prior Austenitic Grain Sizementioning

confidence: 99%

Effect of Microsegregation and Bainitic Reaction Temperature on the Microstructure and Mechanical Properties of a High-Carbon and High-Silicon Cast Steel

Basso

Eres-Castellanos

Tenaglia

et al. 2021

Metals

View full text Add to dashboard Cite

show abstract

“…A third factor that may be favoring having a bimodal distribution is the so-called solute drag effect [60][61][62]. It is well-known that solute atoms (impurities or alloying elements) segregated to the austenite grain boundaries can reduce their mobility and exert a drag force that retards the kinetics.…”

Section: Austenitization Of As-cast Microstructures Prior Austenitic Grain Size (Pags)mentioning

confidence: 99%

Effect of the Microsegregation on Martensitic and Bainitic Reactions in a High Carbon-High Silicon Cast Steel

Basso

Toda‐Caraballo

Eres-Castellanos

et al. 2020

Metals

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Casting processes show some weaknesses. A particular problem is presented when the workpiece needs to be subjected to heat treatments to achieve a desired microstructure. This problem arises from the microsegregation phenomena typically present in cast parts. The effect of the microsegregation on the martensitic and bainitic transformations has been investigated in a high carbon-high silicon cast steel, with the approximate composition Fe-0.8C-2Si-1Mn-1Cr (in wt. %), which was poured into 25 mm keel block-shaped sand molds. The microsegregation maps of Cr, Si, and Mn characterized by electron probe microanalysis (EPMA) show that interdendritic regions are enriched while dendrites are impoverished in these elements, implying that their partition coefficients are lower that the unity (k < 1). As-quenched martensitic and austempered bainitic microstructures (at 230 °C) were obtained and analyzed after applying an austenitization heat treatment at 920 °C (holding for 60 min). The thermal etching method used to reveal the prior austenite grain size showed a bimodal grain size distribution, with larger grains in the dendritic regions (≈22.4 µm) than in the interdendritic ones (≈6.4 µm). This is likely due to both the microsegregation and the presence of small undissolved cementite precipitates. Electron Backscatter Diffraction (EBSD) analysis carried out on the martensitic microstructure do not unveil any differences in misorientation distribution frequency and block size between the dendritic and interdendritic zones related to the microsegregation and bimodality of the austenite grain size. On the contrary, the bainitic transformation starts earlier (incubation time of 80 min), proceeds faster and bainitic ferrite plates are longer in the dendritic zones, were prior austenite grains are larger and impoverish in solute. The presence of these microsegregation pattern leads to the non-uniform development of the bainitic reaction in cast parts, modifying its kinetics and the resulting microstructures, which would probably have a major impact on the mechanical properties.

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“…30 Nitrides are known to inhibit grain growth, if the critical grain radius has not been reached, be it during high-temperature annealing, slab soaking, or during welding in the heat-affected zone. 31,32 Nitrides can also control the grain size evolution during hot working (rolling, forging). Nevertheless, micro-alloying additions that interact with nitrogen have a direct influence on the recrystallization behaviour.…”

Section: Nitridesmentioning

confidence: 99%

Nitrogen and nitride non-metallic inclusions in steel

Burja¹,

Koležnik²,

Župerl³

et al. 2019

Mater. Tehnol.

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The paper deals with the formation of coarse nitride non-metallic inclusions in steel. The thermodynamic calculations for the determination of the equilibrium solubility of nitrogen in the steel melt at a given temperature and chemical composition are presented. Some of the negative effects of excessive nitrogen contents, like blow holes, strain aging and, most importantly, nitride non-metallic inclusion formation are discussed. Five types of the coarse nitride non-metallic inclusions that occur in industrial practice are presented: aluminium, boron, niobium, titanium, and zirconium nitrides. Examples of the negative effect of coarse nitrides from case studies are also shown. The basic thermodynamic tools and values of the parameters for calculating the nitride precipitation in the steel melt are given in the paper.

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Austenite grain growth simulation considering the solute-drag effect and pinning effect

Cited by 28 publications

References 32 publications

Effect of Microsegregation and Bainitic Reaction Temperature on the Microstructure and Mechanical Properties of a High-Carbon and High-Silicon Cast Steel

Effect of Microsegregation and Bainitic Reaction Temperature on the Microstructure and Mechanical Properties of a High-Carbon and High-Silicon Cast Steel

Effect of the Microsegregation on Martensitic and Bainitic Reactions in a High Carbon-High Silicon Cast Steel

Nitrogen and nitride non-metallic inclusions in steel

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