Effect of chemical banding on the local hardenability in AISI 4340 steel bar

Penha, Renata Neves; Vatavuk, Jan; Couto, Antônio Augusto; Pereira, Silvio André de Lima; Sousa, Silas Aragão de; Canale, Lauralice de Campos Franceschini

doi:10.1016/j.engfailanal.2015.03.024

Cited by 19 publications

(10 citation statements)

References 5 publications

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“…This is because solid-state transformations are influenced by the chemical composition, and therefore, a chemical heterogeneity in the parts could generate the presence of brittle phases after a particular thermal cycle, obtaining a poor mechanical behavior [12][13][14][15]. On the other hand, when castings are subjected to heat treatments the presence of microsegregation could generate microstructures in which the matrix phases formed during cooling are distributed heterogeneously [16][17][18][19][20]. For example, this microsegregation often promotes, in wrought steel parts, after rolling, microstructures that can display what it is named as "microstructural banding", which has its origin in the presence of a "chemical banding", and which can be described as a banded appearance with alternating bands (consisting of planar arrays) of two or more pairs of phases at room temperature: ferrite, pearlite, bainite, and/or martensite [17][18][19].…”

Section: Introductionmentioning

confidence: 99%

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

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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: Introductionmentioning

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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“…[5][6][7][8][9][10][11]. In addition, when castings are subjected to heat treatments in the presence of microsegregation, these chemical gradients could generate microstructures in which the matrix phases formed during cooling are distributed heterogeneously [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. For example, this microsegregation often promotes, in wrought steel parts, after rolling, microstructures displaying a banded appearance with the alternating bands consisting of planar arrays of two or more pairs of the main room temperature phases found in steels: ferrite, pearlite, bainite and/or martensite.…”

Section: Introductionmentioning

confidence: 99%

“…For example, this microsegregation often promotes, in wrought steel parts, after rolling, microstructures displaying a banded appearance with the alternating bands consisting of planar arrays of two or more pairs of the main room temperature phases found in steels: ferrite, pearlite, bainite and/or martensite. [7,14,[17][18][19]. There have been several studies concerned with the effect of banding on mechanical properties [13,15,17,20,21].…”

Section: Introductionmentioning

confidence: 99%

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

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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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“…Our critical rate of pure martensitic transformation is 0.5 • C. Overall, their diagram is shifted to the left. Likewise, a group of authors, Samadi Shahreza et al [39] and Penha et al [40], dealt with this issue, and their resulting CCT diagrams are also slightly shifted to the left. Nasar A. Ali [41] and Popescu et al [42] investigate a very similar steel with a slightly higher content of Cr and Ni.…”

Section: Cct Diagram Aisi 4340 Steelmentioning

confidence: 99%

Effect of Selected Cooling and Deformation Parameters on the Structure and Properties of AISI 4340 Steel

et al. 2020

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The paper is focused on investigation of the high-strength AISI 4340 steel at various temperature and deformation conditions. The article is divided into two specific analyses. The first is to examine the dilatation behavior of the steel at eight different cooling rates, namely, 100, 10, 5, 1, 0.5, 0.1, 0.05 and 0.01 °C·s−1. The mapping of the phase transformations due to varying cooling rates from the austenitizing temperature of 850 °C allows the construction of the CCT diagram for a given high-strength steel. These dilatation curves were also compared with the metallography of the selected samples for the proper construction of the CCT diagram. A further analysis of the high temperature deformation of high strength steel AISI 4340 was performed in the range of temperature 900–1200 °C, and the strain rate was in the range from 0.001 to 10 s−1 with maximum value of the true strain 0.9. Changes in the microstructure were observed using light optical microscopy (LOM). The effect of hot deformation temperature on true stress, peak stress and true strain was investigated. The hardness of all deformed samples, depending on the temperature, the deformation rate and the peak stress σp overall together related with hardness, has also been evaluated.

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Effect of chemical banding on the local hardenability in AISI 4340 steel bar

Cited by 19 publications

References 5 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

Effect of Selected Cooling and Deformation Parameters on the Structure and Properties of AISI 4340 Steel

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