Strengthening from Nb-rich clusters in a Nb-microalloyed steel

Xie, Kelvin Y.; Zheng, Tianxiao; Cairney, Julie M.; Kaul, Harold R; Williams, J. G.; Barbaro, Frank; Killmore, Chris R.; Ringer, Simon P.

doi:10.1016/j.scriptamat.2012.01.029

Cited by 96 publications

(45 citation statements)

References 19 publications

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“…Reported uncertainity represents a standard deviation calculated from the composition of all the clusters in the reconstruction. Figure 7(b), close-up of these clusters, shows that they are only a few atomic layers thick, consistent with other studies where these monoatomic thick clusters are identified as GP-zone-like clusters [17,26,41] and their shape is thought to be more energetically favorable for nucleation. [26] This lack of large (Ti,Nb)(C) is consistent with observations in STEM-HAADF images and also with a few other experimental results.…”

Section: B Precipitates In Alloysupporting

confidence: 88%

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Atom Probe Tomography Study of Multi-microalloyed Carbide and Carbo-Nitride Precipitates and the Precipitation Sequence in Nb-Ti HSLA Steels

Kapoor

O’Malley

Thompson

2016

Metall Mater Trans A

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Composition analysis of carbide and carbo-nitride precipitates was performed for two Nb-Ti microalloyed steels with yield strengths of 750 and 580 MPa using an atom probe study. In the high-Ti 750 MPa steel, Ti-rich (Ti,Nb)(C,N) and Ti-rich (Ti,Nb)(C) precipitates were observed. In the high-Nb 580 MPa steel, a Ti-rich (Ti,Nb)(C,N) precipitate and (Ti,Nb)(C) clusters were noted. These (Ti,Nb)(C) clusters in the high-Nb 580 MPa steel were smaller than the (Ti,Nb)(C) precipitates in high-Ti 750 MPa steel. In general, a larger number of precipitates were found in the high-Ti 750 MPa steel. This difference in the number density of the precipitates between the two steels is attributed to the difference in Ti content. Combining the atom probe tomography results and thermodynamic calculations, the precipitation sequence in these alloys was inferred to be the following: as the temperature decreases, TiN precipitates out of the solution with successive (Ti,Nb)(C,N) layers of varying composition forming on these Ti-rich precipitates. Once N is depleted from the solution, a second set of (Ti,Nb)(C) precipitates in a similar manner in the matrix and also onto the carbo-nitride phase. This observation is consistent with previous observations in high-strength low-alloy steels containing comparable amounts of only Nb. It was noted that the amount of Nb, Nb/(Nb + Ti), in the precipitates decreased from 0.20 to 0.04 with the size of the precipitate. We believe that this is due to the Nb supersaturation in the matrix when these precipitates nucleate.

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Section: B Precipitates In Alloysupporting

confidence: 88%

“…This observation-no large precipitates but instead the formation of GP-zone-like clusters-has also been reported in other hot-rolled steels with only Nb. [17,22,41] V. CONCLUSIONS 1. Nine precipitates were found after studying 20 samples, totaling approximately 300 million ions, in alloy 1.…”

Section: Precipitation and Clustering Behavior In Alloy 1 Andmentioning

confidence: 97%

Atom Probe Tomography Study of Multi-microalloyed Carbide and Carbo-Nitride Precipitates and the Precipitation Sequence in Nb-Ti HSLA Steels

Kapoor

O’Malley

Thompson

2016

Metall Mater Trans A

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“…This is in contrast to the lowest precipitation strengthening contribution calculated for the MoNbV-steel subjected to the lower strain processing. The additional strengthening in this condition could originate from two sources: (i) solid solute atoms of Mo, C and, possibly, N; and (ii) atom clusters of Mo, Nb and V. Substantial strengthening from atom clusters was recently reported for microalloyed steels [80][81][82][83]. In spite of qualitatively similar effects of Mo and Cr on solubility of other elements, in the CrNbV-steel a possible strengthening from solute atoms and atom clusters did not exhibit itself.…”

Section: Microstructure-mechanical Properties Relationship: Role Of Smentioning

confidence: 79%

Comparative Effect of Mo and Cr on Microstructure and Mechanical Properties in NbV-Microalloyed Bainitic Steels

Kostryzhev

Singh

Chen

et al. 2018

Metals

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Steel product markets require the rolled stock with further increasing mechanical properties and simultaneously decreasing price. The steel cost can be reduced via decreasing the microalloying elements contents, although this decrease may undermine the mechanical properties. Multi-element microalloying with minor additions is the route to optimise steel composition and keep the properties high. However, this requires deep understanding of mutual effects of elements on each other's performance with respect to the development of microstructure and mechanical properties. This knowledge is insufficient at the moment. In the present work we investigate the microstructure and mechanical properties of bainitic steels microalloyed with Cr, Mo, Nb and V. Comparison of 0.2 wt. % Mo and Cr additions has shown a more pronounced effect of Mo on precipitation than on phase balance. Superior strength of the MoNbV-steel originated from the strong solid solution strengthening effect. Superior ductility of the CrNbV-steel corresponded to the more pronounced precipitation in this steel. Nature of these mechanisms is discussed.

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“…Therefore, C can be highly enriched at the austenite grain boundaries [151]. The enrichment of C on the prior-austenite grain boundaries was directly observed using atom probe microscopy [208,209]. A study by Kostryzhev et al [209] is shown in Figure 5-12 as an example.…”

Section: Influence Of C On Austenite Grain Growth Behaviourmentioning

confidence: 99%

Thermomechanical Processing of Structural Steels with Dilute Niobium Additions

Cui¹,

Patel²,

Palmiere³

2015

HSLA Steels 2015, Microalloying 2015 &Amp; Offshore Engineering Steels 2015

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-i - AbstractIn this thesis, the influence of various dilute Nb additions (0.005-0.02 wt%) on austenite microstructure evolution along thermomechanical processing, in terms of austenite recrystallisation and grain growth, were investigated using steels with three carbon content levels.At the homogenisation temperature of 1250°C, all dilute Nb additions were dissolved in low carbon steels whereas the Nb dissolution limits for 0.4 wt% and 0.6 wt% C steels were 0.012 wt% and 0.08 wt%, respectively. Dilute Nb additions did not show significant influence on homogenised austenite grain size. The dramatic increase in C contents was more influential, which decreased the homogenised austenite grain size.The influence of dilute Nb additions and C contents on dynamic recrystallisation behaviour was studied by rough rolling at high deformation temperature with low strain rate. The dilute Nb additions were found to increase the critical strain of dynamic recrystallisation whereas C contents showed no influence on the dynamic recrystallisation behaviour.The austenite recrystallisation behaviour after finish rolling and after the holding period between finishing passes were studied by means of interrupted plane strain compression (PSC) tests and double hit PSC tests. It was found that with low Nb supersaturation, recrystallisation happened prior to Nb precipitation. Solute Nb in austenite delayed the onset of austenite recrystallisation through solute drag effect.With high Nb supersaturation, Nb precipitation occurred before the onset of recrystallisation which completely retarded austenite recrystallisation.The austenite grain growth during the holding period between finish rolling passes was studied by the evolution of prior-austenite grain size before and after the 20s holding period at the highest finish rolling temperature (1050°C). There was no Nb precipitation found and the difference in austenite grain growth behaviour was Abstract -iiattributed to the solute drag effect from both Nb and C in solution. It was found that Nb in solution suppressed austenite grain growth. However, the effectiveness of solute Nb in suppressing austenite grain growth was affected by the C content. Acknowledgement

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Strengthening from Nb-rich clusters in a Nb-microalloyed steel

Cited by 96 publications

References 19 publications

Atom Probe Tomography Study of Multi-microalloyed Carbide and Carbo-Nitride Precipitates and the Precipitation Sequence in Nb-Ti HSLA Steels

Atom Probe Tomography Study of Multi-microalloyed Carbide and Carbo-Nitride Precipitates and the Precipitation Sequence in Nb-Ti HSLA Steels

Comparative Effect of Mo and Cr on Microstructure and Mechanical Properties in NbV-Microalloyed Bainitic Steels

Thermomechanical Processing of Structural Steels with Dilute Niobium Additions

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