Structure-dependent intergranular segregation of phosphorus in austenite in a Ni-Cr steel

Ogura, Tsugio; McMahon, C.J.; Feng, H. C.; Vítek, V.

doi:10.1016/0001-6160(78)90147-5

Cited by 107 publications

(29 citation statements)

References 10 publications

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“…In general, these deviations do not exceed 2-3". l 7 In the case of the bicrystal used in the present study, the deviation was <2" from the X3 relationship. Because the (112) orientation of the grain boundary is the most stable,28 we can suppose that the actual structure of the grain boundary will be formed by the ideal (112) boundary with excess small-angle grain boundary (or dislocation wall).…”

Section: Discussionmentioning

confidence: 54%

“…The reduced probability of any segregation effect at coherent twin boundaries is explained by the lack of free volume, which could accommodate misfitting solute atoms. 7 On the other hand, Herschitz et al observed strong segregation of Nb and Fe at stacking faults in the respective cobalt binary alloys by means of the atom probe field ion microscopy (AP-FIM) technique, and described it by solute interactions of the Fowler type.I4 The segregation effects were found also in bicrystals with the symmetrical { 112) grain boundary (i.e. coherent twin boundary) of both an Fe-6 at.% Si alloy after slow cooling from the melting temperat~re'~ and an Fe-12.9 at.% Si alloy quenched after reaching equilibrium segregation at various temperatures.I6…”

Section: Introductionmentioning

confidence: 99%

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Temperature dependence of the phosphorus segregation at the twin boundary in an Fe–4 at.% Si alloy

Lejček

Hofmann

1990

Surface & Interface Analysis

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AES of in situ fractured bicrystals of an F e 4 at.% Si alloy containing traces of phosphorus was used to study the temperature dependence of the segregation at the symmetrical (112) (coherent twin) grain boundary between 773 and 1173 K. The observed enrichment of P decreases with temperature, whereas that of Si increases slightly. This behaviour is described by a mutual repulsive interaction coefficient a ' = 92 kJ mol-' of P and Si and the corresponding pure binary segregation enthalpies AHp' = -7.9 kJ mol-' and A@, = -3.0 kJ mol-', the absolute values of which are considerably lower than those reported for polycrystallioe samples of Fe-P and FeSi. The differences are explained on the basis of orientation, concentration and interaction effects. INTRODUCTIONThe structure of grain boundaries is one of the essential features that affect the properties of materials. For example, it is responsible for plasticity, corrosion resistance, recrystallization behaviour, etc.' The structure of a grain boundary controls its chemical composition to such an extent that the anisotropy of grain boundary segregation is well detectable. First suggestions of this anisotropy were concluded from the great scatter of experimental data measured at various facets of polycrystalline materials fractured in situ in an ultrahigh vacuum (UHV) chamber of an Auger electron spectrometer.z-6 Some implications were made also on the basis of corrosion behaviour of differently oriented grain b~undaries.~.' Direct evidence of the segregation anisotropy was obtained from AES investigations of defined grain boundaries in bicrystalline sample^.^-'^ These results reflect the differences between 'special' and 'general' grain boundaries : the amount of segregants usually has been found to be low in the former case. However, the question still remains open whether impurities and/or alloying elements segregate at the coherent twin boundaries or not. The difficulty in finding an answer to this question is due to the fact that the segregation at the X3 special grain boundaries is expected to be very low. In addition, these boundaries are usually very resistant to intercrystalline brittle fracture, which is necessary for measurements of chemical composition by the most frequently used AES technique.Several papers dealing with measurements of segregation in polycrystalline materials attempt to make suggestions about the chemical composition of twin boundaries, e.g. Refs 7 and 8. In these papers, AES and scanning transmission electron microscopy (STEM) data, respectively, are compared with the degree of grain boundary etching and an extrapolation is made to the chemically intact coherent twin boundaries. Ogura et al. conclude that coherent twin boundaries in austenite in an NiCr steel do not absorb P at all, as far as the etching technique can detect, but incoherent twin boundaries do.' The same conclusion was reached by Beaunier et al.' in an Ni-S system. The reduced probability of any segregation effect at coherent twin boundaries is explained by the lack of f...

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Section: Discussionmentioning

confidence: 54%

Section: Introductionmentioning

confidence: 99%

Temperature dependence of the phosphorus segregation at the twin boundary in an Fe–4 at.% Si alloy

Lejček

Hofmann

1990

Surface & Interface Analysis

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“…For example, phosphorus is one of the typical metalloid impurities causing intergranular brittle fracture in continuous casting because the grain boundary segregation of phosphorus reduces the cohesion strength between grains. [15][16][17][18][19] T. Ogura et al 12) found that the amount of phosphorus segregation was larger at incoherent boundaries in Ni-Cr steel. On the other hand, S-H Song 21) showed the hot ductility was improved by the grain boundary segregation of boron and sulphur in 2.25Cr-1Mo steel.…”

Section: Introductionmentioning

confidence: 99%

Effect of Titanium Addition on High Temperature Workability of High Manganese Austenitic Steel

Kim

Bae

et al. 2018

ISIJ Int.

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In the present study, the high temperature workability of high manganese austenitic steel has been examined to prevent the grain boundary embrittlement cracking problems in the continuous casting process. As-cast Fe-22Mn-0.4C steel exhibited poor hot ductility behaviors at 900°C tensile test. Phosphorus segregation and BN precipitation at grain boundaries were mainly responsible for this deterioration. In order to enhance the hot ductility, titanium was added to this steel, and high temperature workability was compared in view of reduction of area in tensile test at 900°C. BN precipitation at grain boundaries was effectively suppressed by the formation of interior Ti(C,N) precipitates. Furthermore, phosphorus atoms, a grain boundary embrittlement element, were observed to segregate at Ti(C,N) interfaces in Auger electron spectroscopy and atom probe tomography. These results show that titanium addition in Fe-22Mn-0.4C steel can effectively improve the high temperature workability by decreasing the segregation of phosphorus at grain boundary.KEY WORDS: high manganese austenite steel; high temperature workability; grain boundary segregation; Ti(C,N) precipitate; atom probe tomography.

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“…It was discovered [4][5][6] that the channel-like grain boundary grooves will appear in steels with impurity segregation on prior austenite grain boundaries after etching the polished specimens in suitable solutions and the depth of grain boundary grooves can be a measure of intergranular impurity segregation. Based on these observations, a simple grain boundary etching method (GEM) [7,8] has been developed to analyse the intergranular P-segregation in iron-base alloys. The mean grain boundary groove depth was determined as the quantitative measurement of intergranular P-segregation, either by electroplating nickel on the etched surface and then measuring the penetration of nickel into the grooves [7] or by metallographically polishing the etched specimen and measuring the change of the dimension of hardness indentation,…”

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confidence: 99%

A SEM (scanning electron microscopy)-based method to evaluate impurity segregation to prior austenite grain boundaries in high strength steels

Cao

1989

J Mater Sci

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The depth of grain boundary grooves on the etched surface of high strength Cr-Ni steels has been determined as a measure of P-segregation to prior austenite grain boundaries by a SEM (Scanning Electron Microscopy)-based grain boundary etching method (GEM). The mean depth and distribution of the depth can be decided by stereoscopy on the SEM micrographs of the replica of the etched surface. The results showed that the cast steel has less, but nonuniform P-segregation and the high temperature austenitization reduced the P-segregation on prior austenite grain boundaries in both steels. IntroductionIt is well known [1][2][3] that the impurity segregation to prior austenite grain boundaries has a significant influence on the mechanical properties of high strength steels. Therefore, a quantitative evaluation of this segregation is necessary for clarifying the origins of the variation of mechanical properties of steels with composition, processing and environment etc. Auger Electron Spectroscopy (AES) can be applied to detect the impurity atoms existing in the extreme thin layer of grain boundary directly. However, AES can not be used to analyse the grain boundary segregation in the case where the steels do not break intergranularly. In addition, there are some questions about the validity of AES results due to the change in nature and quantity of surface atoms during the preparation and transfer of AES specimens. As stated below, a meaningful result could not be obtained by AES in materials with non-uniform distribution of impurity. It was discovered [4][5][6] that the channel-like grain boundary grooves will appear in steels with impurity segregation on prior austenite grain boundaries after etching the polished specimens in suitable solutions and the depth of grain boundary grooves can be a measure of intergranular impurity segregation. Based on these observations, a simple grain boundary etching method (GEM) [7,8] has been developed to analyse the intergranular P-segregation in iron-base alloys. The mean grain boundary groove depth was determined as the quantitative measurement of intergranular P-segregation, either by electroplating nickel on the etched surface and then measuring the penetration of nickel into the grooves [7] or by metallographically polishing the etched specimen and measuring the change of the dimension of hardness indentation,

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Structure-dependent intergranular segregation of phosphorus in austenite in a Ni-Cr steel

Cited by 107 publications

References 10 publications

Temperature dependence of the phosphorus segregation at the twin boundary in an Fe–4 at.% Si alloy

Temperature dependence of the phosphorus segregation at the twin boundary in an Fe–4 at.% Si alloy

Effect of Titanium Addition on High Temperature Workability of High Manganese Austenitic Steel

A SEM (scanning electron microscopy)-based method to evaluate impurity segregation to prior austenite grain boundaries in high strength steels

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