Distribution of boron in gamma iron grains

Goldhoff, R. M.; Spretnak, J. W.

doi:10.1007/bf03398308

Cited by 14 publications

(7 citation statements)

References 8 publications

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“…They concluded that in carbon-free α-Fe with boron, boron is present as substitutional solute, as no peak is detected. Substitutional dissolution of B in α-Fe has been reported by Nicolson [88] and also by Goldhoff and Spretnak [89] based on the lattice parameter measurement using X-ray.…”

Section: Boron In α-Fementioning

confidence: 73%

Boron in Heat‐Treatable Steels: A Review

Sharma

Ortlepp

Bleck

2019

steel research int.

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The science and technology of boron addition to heat‐treatable steels are explained. The aim is to address the following: How to add boron to steel (i.e., the manufacturing aspects of boron addition to steel)? What precautions are necessary when alloying boron to steel, in terms of composition (mainly nitrogen, aluminum, and titanium contents), processing and heat treatment (i.e., material and process robustness and reproducibility for a consistent steel quality)? Where does boron go in steel (i.e., the state of boron, interstitial or substitutional solute, precipitate or a complex with other alloying elements; as well as the location of boron, i.e., dissolved as a solute in the grain or segregated at the grain boundary)? Which characterization methods are suitable for the detection of the very small amounts of boron (<30 wt ppm) in heat‐treatable steels? What does boron do in steel (i.e., its effect on hardenability and mechanical properties, specifically impact toughness)? How does it do and what it does (i.e., the physical mechanism by which it influences the properties)? How much boron is really required to achieve the desired properties in heat‐treatable steels (i.e., recommendations for the optimum boron content)?

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Section: Boron In α-Fementioning

confidence: 73%

Boron in Heat‐Treatable Steels: A Review

Sharma

Ortlepp

Bleck

2019

steel research int.

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“…1,2) The grain boundary energy of austenite is decreased by the segregation of boron and finally inhibits ferrite nucleation. [3][4][5][6][7] The effect of boron on hardenability is utilized in the steel industry to strengthen steels; [9][10][11][12] however, some technical issues associated with the use of boron still remain, such as instability of the hardenability, which is caused by the formation of Fe 23 (CB) 6 , 13) and a substantial decrease in toughness, which is caused by an increase in the martensite-austenite (MA) constituent in the microstructure. 14) Furthermore, the simultaneous addition of Mo or Nb along with boron is known to result in a stronger effect on the hardenability.…”

Section: Introductionmentioning

confidence: 99%

“…The literature [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] contains abundant reports related to the mechanism by which boron affects the formation of microstructures in steel; however, studies that consider the effects of both the thermodynamics and kinetics of boron segregation at the austenite grain boundary on the nucleation and the growth of ferrite from austenite are few. Shibata et al studied the influence of boron segregated at the grain boundary on the hardenability of steels 17) using the alphaparticle track etching (ATE) method.…”

Section: Introductionmentioning

confidence: 99%

Kinetic Model of the γ to α Phase Transformation at Grain Boundaries in Boron-bearing Low-alloy Steel

2014

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The effect of boron on the nucleation and growth of ferrite at austenite grain boundaries is examined theoretically under the assumption that the junction of 4-austenite grain boundaries (i.e., the 4-grain junctions) are the dominant nucleation sites of ferrite. Boron segregates to the austenite grain boundaries and reduces the grain-boundary energy; it thereby retards ferrite nucleation at the grain boundary. The retardation is expressed as a decrease in nucleation density due to an increase in the critical activation energy for nucleation, and the calculated value of the fraction of active nucleation sites is in satisfactory agreement with the experimental results. The reduction of the austenite grain-boundary energy, which we obtained by applying the Gibbs isotherm for adsorption to the boron segregation, is of the same order of magnitude as the reduction is deduced from the results of calculations for a decrease in the nucleation density based on experimental results. The growth of ferrite was calculated using DICTRA, which yielded both the volume fraction and the grain size of transformed ferrite as functions of time; the results agreed with the experimental results. This agreement suggests that the influence of boron on the growth rate is negligible. However, the increase in the size of the diffusion cell due to the addition of boron is considered to be the main reason for the slightly larger grain size of ferrite compared with that in boron-free steel; this result is also in good agreement with experimental observations.

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“…Many researchers [8][9][10]13,[15][16][17] have used Mo-B steel to study the B segregation phenomenon because the addition of Mo in B-bearing steel suppresses carbon diffusion and thus prevents solute B from forming Fe 23 (C,B) 6. [15,16] Ti was added to the steels to sequester the nitrogen as TiN.…”

Section: Methodsmentioning

confidence: 99%

“…B atoms are easily segregated to the austenite grain boundaries during general heat treatment and have a strong tendency to interact with lattice imperfections. [6] In general, the grain boundary segregation of B in steel occurs by two mechanisms: equilibrium and nonequilibrium segregation. [7] Equilibrium grain boundary segregation (EGS) occurs by the movement of solute atoms from inside the grain matrix to loosely packed regions such as grain boundaries, thus reducing the grain boundary free energy.…”

Section: The Addition Of a Small Amount Of Boron (B)mentioning

confidence: 99%

Cooling Rate Dependence of Boron Distribution in Low Carbon Steel

Mun

Shin

Cho

et al. 2011

Metall Mater Trans A

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The behavior of boron (B) segregation to austenite grain boundaries in low carbon steel was studied using particle tracking autoradiography (PTA) and secondary ion mass spectroscopy (SIMS). An effective time method was used to compare the cooling rate (CR) dependence of this segregation during continuous cooling and its time dependence during isothermal holding. Comparison of these segregation behaviors has confirmed that the CR dependence of B segregation agrees well with its time dependence and is mainly a result of the phenomenon of nonequilibrium segregation. Based on the CR dependence of B segregation, the continuous cooling transformation behavior of B-bearing steel as compared with B-free steel was also investigated using dilatometry and microstructural observations. The addition of a small amount of B to low carbon steel retarded significantly the austenite-to-ferrite transformation and finally expanded the range of cooling programs that result in the formation of bainitic microstructures. Analysis of the B distribution has confirmed that this retardation effect of B on ferrite transformation is attributed to the CR dependence of B segregation to austenite grain boundaries during cooling after austenitization.

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Distribution of boron in gamma iron grains

Cited by 14 publications

References 8 publications

Boron in Heat‐Treatable Steels: A Review

Boron in Heat‐Treatable Steels: A Review

Kinetic Model of the γ to α Phase Transformation at Grain Boundaries in Boron-bearing Low-alloy Steel

Cooling Rate Dependence of Boron Distribution in Low Carbon Steel

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