Nitrogen partitioning between matrix, grain boundaries and precipitates in high-alloyed austenitic steels

Petrov, Yu. N.; Gavriljuk, V.G.; Berns, Hans; Escher, C.

doi:10.1016/s1359-6462(98)00488-6

Cited by 31 publications

(14 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the other hand, it is known that nitrogen has less tendency to cause grain boundary segregation in steel, as compared to carbon. [20][21][22] This agrees well with the experimental results that k y is hardly influenced by nitrogen. The enlarged k y by nitrogen mentioned above might be due to the large amount of solute nitrogen in austenite matrix leading to the high concentration of nitrogen at grain boundary even though the segregation coefficient is small.…”

Section: Change In Hall-petch Coefficient By Grainsupporting

confidence: 88%

Effect of Interstitial Elements on Hall–Petch Coefficient of Ferritic Iron

et al. 2008

View full text Add to dashboard Cite

Here, on the assumption that the classical grain boundary segregation theory would be applied to the case of this study, namely, carbon in ferritic steel, the Hall-Petch coefficient was compared with the concentration of carbon at grain boundary. According to the MacLean's theory, 17) solute carbon concentration segregated at ferrite grain boundary at 973 K is calculated by following equation:In this equation, [at%C], Q and R are the total carbon concentration in solid solution, the activation energy of carbon for grain boundary segregation and the gas constant, respectively. As for the value of Q, 78 kJ/mol estimated by Grabke 18) was taken. Figure 6 shows relationship between k y and segregated carbon content calculated by Eq. (3). k y value tends to increase linearly with increasing segregated carbon content, which suggests that grain boundary segregation of interstitial alloy elements significantly prevents the yielding of ferritic steel. Only 60 ppm carbon causes marked grain boundary segregation to 80 at%, resulting in the enlargement of the k y from 100 (in IF-steel) to 550 MPa · mm 1/2 . The solubility of carbon was reported to be approximately 60 ppm even at ambient temperature 19) in Fe-C binary alloy. Therefore, it could be understood that the similar k y values, around 600 MPa · mm 1/2 , have been reported in lots of previous studies on grain refinement strengthening of ferritic steels except for IF-steels. On the other hand, it is known that nitrogen has less tendency to cause grain boundary segregation in steel, as compared to carbon. [20][21][22] This agrees well with the experimental results that k y is hardly influenced by nitrogen. The enlarged k y by nitrogen mentioned above might be due to the large amount of solute nitrogen in austenite matrix leading to the high concentration of nitrogen at grain boundary even though the segregation coefficient is small. Conclusions(1) IF-steel has a low Hall-Petch coefficient of approximately 100 MPa · mm 1/2 . The Hall-Petch coefficient of ferritic iron monotonously increases with increasing solute carbon content, and it levels off at 550-600 MPa · mm 1/2 when the solute carbon content reaches 60 ppm. On the other hand, the solute nitrogen hardly affects the Hall-Petch coefficient.(2) The increase in Hall-Petch coefficient by solute carbon seems to be derived from the grain boundary segregation of carbon atoms. The small effect of solute nitrogen on Hall-Petch coefficient could be explained by the less tendency of nitrogen atoms to cause grain boundary segregation. ISIJ, Tokyo, Japan, (1991), 762. 12) V. G. Gavriljuk, H. Berns, C. Escher, N. I. Glavatskaya, A. Sozinov and Yu. N. Petrov: Mater. Sci. Forum, 318-320 (1999)

show abstract

Section: Change In Hall-petch Coefficient By Grainsupporting

confidence: 88%

Effect of Interstitial Elements on Hall–Petch Coefficient of Ferritic Iron

et al. 2008

View full text Add to dashboard Cite

show abstract

“…In ferritic and austenitic steels, carbon significantly segregates along grain boundaries, while the segregation of nitrogen along grain boundaries is not obvious. 22,23) Therefore, during isothermal ageing treatments, precipitation of chromium nitride along grain boundaries can be suppressed as compared to the precipitation of chromium carbides. With increasing nitrogen content, the formation of Cr 23 C 6 -type carbides can be retarded because the substitution of small amount of nitrogen in Cr 23 C 6 could result in its complete dissolution, 24) causing the amount of Cr 2 N-type nitrides to be significantly increased.…”

Section: Discussionmentioning

confidence: 99%

Precipitation of Secondary Phases in Lean Duplex Stainless Steel 2101 during Isothermal Ageing

et al. 2010

View full text Add to dashboard Cite

The DSS ingot was made by standard vacuum melting and casting, which possessed duplex ferritic-austenitic mi- 286© 2010 ISIJ ISIJ International, Vol. 50 (2010) In the present paper, the precipitation behavior of secondary phases in Lean Duplex Stainless Steel (LDX) 2101 had been studied. The alloy has a typical ferritic-austenitic duplex structure after solution treatment. Isothermal ageing treatments were carried out over the temperature range from 700 to 850°C for the period between 2 min and 1 440 min. Cr 2 N-type nitrides were formed as the main product of precipitates, together with small amount of Cr 23 C 6 -type carbides. Increase of N content and decrease of Cr and Mo contents in the steel had led to the absence of s-phase. Due to the solid solution strengthening by interstitial atoms, the hardness value of austenite was measured to be higher than that of ferrite. With increasing the isothermal ageing time, precipitates were observed to be preferentially nucleated at the d/g interface and grown toward the d phase. The d/g interfce migrated from the precipitate particles into d phase, leaving the precipitates behind along the original interfaces, which could increase the size of the secondary austenite (gЈ) phase and decrease the hardness of both austenite and ferrite. Inside gЈ phase, the hardness was measured to increase from about 3.20 GPa at the original interface to about 3.75 GPa at the newly formed interface of d/gЈ. The isothermal kinetics for the precipitation of secondary phases was measured to obey the JMAK-type law. The TTT (time-temperature-transformation) curve was constructed based on the measurements, which seems to have resulted from the overlap of two different precipitated products. The average impact energy at room temperature for the sample after solid solution treatment was measured to be 105 J. When 2 % secondary phases were precipitated during ageing, the impact energy decreased to about 43 J, reduced by about 59 % as compared with the as-annealed sample, indicating that formation of secondary phases can result in dramatic decrease of steel toughness.

show abstract

“…In the vicinity of the nitrogen atoms, the concentration of s-electrons in the fcc iron increases, as was shown by ab initio calculations [101] and experimental studies on the electronic structure [99]. In the surroundings of the nitrogen atoms, the free electrons rearrange such that the energy of elastic distortions in the crystal lattice decreases [102]. The local electron density was shown to have a major influence on the dislocation interactions with nitrogen and can be attributed to the SFE in Fe–Cr–Mn alloys [101].…”

Section: Stacking Fault Energy In the Fe–cr–mn–n Systemmentioning

confidence: 98%

Nitrogen in chromium–manganese stainless steels: a review on the evaluation of stacking fault energy by computational thermodynamics

Mosecker

Saeed-Akbari

2013

Science and Technology of Advanced Materials

View full text Add to dashboard Cite

Nitrogen in austenitic stainless steels and its effect on the stacking fault energy (SFE) has been the subject of intense discussions in the literature. Until today, no generally accepted method for the SFE calculation exists that can be applied to a wide range of chemical compositions in these systems. Besides different types of models that are used from first-principle to thermodynamics-based approaches, one main reason is the general lack of experimentally measured SFE values for these steels. Moreover, in the respective studies, not only different alloying systems but also different domains of nitrogen contents were analyzed resulting in contrary conclusions on the effect of nitrogen on the SFE. This work gives a review on the current state of SFE calculation by computational thermodynamics for the Fe–Cr–Mn–N system. An assessment of the thermodynamic effective Gibbs free energy, , model for the phase transformation considering existing data from different literature and commercial databases is given. Furthermore, we introduce the application of a non-constant composition-dependent interfacial energy, бγ/ε, required to consider the effect of nitrogen on SFE in these systems.

show abstract

Nitrogen partitioning between matrix, grain boundaries and precipitates in high-alloyed austenitic steels

Cited by 31 publications

References 13 publications

Effect of Interstitial Elements on Hall–Petch Coefficient of Ferritic Iron

Effect of Interstitial Elements on Hall–Petch Coefficient of Ferritic Iron

Precipitation of Secondary Phases in Lean Duplex Stainless Steel 2101 during Isothermal Ageing

Nitrogen in chromium–manganese stainless steels: a review on the evaluation of stacking fault energy by computational thermodynamics

Contact Info

Product

Resources

About