Microstructural evolution in a new 770MPa hot rolled Nb–Ti microalloyed steel

Misra, R.D.K.; Nathani, H.; Hartmann, J.E.; Siciliano, Fulvio

doi:10.1016/j.msea.2004.11.041

Cited by 230 publications

(108 citation statements)

References 16 publications

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“…The average dislocation density in ferrite increased with a decrease in the finish deformation temperature from 4.5 ± 0.5 9 10 13 m À2 for 1348 K (1075°C) to 4.6 ± 0.5 9 10 13 m À2 for 1248 K (975°C) and to 9.5 ± 1.1 9 10 13 m À2 for 1098 K (825°C). The measured values of dislocation density correspond to those reported earlier for ferrite in carbon [23,24] and Nb-microalloyed steels [9,12,19,25] processed in the same temperature range, i.e., above A r3 temperature of austenite-to-ferrite transformation; however, they are several times lower than those after finish rolling in the a + c phase field (2.3 À 4.0 9 10 14 m À2 [26] ) and more than 10 times lower than after finish rolling in ferrite (7 9 10 14 m À2 [9] ).…”

Section: Tem Study Of Dislocation Structuresupporting

confidence: 87%

“…The particle size, morphology, and chemistry observed in this work correspond to those reported for similar steel compositions and processing parameters. [16][17][18][19][20][21][22] The precipitate parameters and compositions varied with TMP schedule (Table I; Figure 5). For particles in the >20 nm size range, the average diameter was the smallest, and the number density and volume fraction were the highest for the 1248 K (975°C) deformation temperature TMP schedule, compared to other two schedules.…”

Section: A Optical Microscopymentioning

confidence: 99%

“…Fig. 8-Effect of the finish deformation temperature on (a) dislocation density [9,12,19,25,26] and (b) the work hardening contribution to the yield stress estimated using Eq. [5].…”

Section: Effect Of Strengthening Mechanisms On the Yield Stressmentioning

confidence: 99%

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Strengthening Mechanisms in Thermomechanically Processed NbTi-Microalloyed Steel

Kostryzhev

Marenych

Killmore³

et al. 2015

Metall Mater Trans A

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The effect of deformation temperature on microstructure and mechanical properties was investigated for thermomechanically processed NbTi-microalloyed steel with ferrite-pearlite microstructure. With a decrease in the finish deformation temperature at 1348 K to 1098 K (1075 °C to 825 °C) temperature range, the ambient temperature yield stress did not vary significantly, work hardening rate decreased, ultimate tensile strength decreased, and elongation to failure increased. These variations in mechanical properties were correlated to the variations in microstructural parameters (such as ferrite grain size, solid solution concentrations, precipitate number density and dislocation density). Calculations based on the measured microstructural parameters suggested the grain refinement, solid solution strengthening, precipitation strengthening, and work hardening contributed up to 32 pct, up to 48 pct, up to 25 pct, and less than 3 pct to the yield stress, respectively. With a decrease in the finish deformation temperature, both the grain size strengthening and solid solution strengthening increased, the precipitation strengthening decreased, and the work hardening contribution did not vary significantly. The effect of deformation temperature on microstructure and mechanical properties was investigated for thermomechanically processed NbTi-microalloyed steel with ferrite-pearlite microstructure. With a decrease in the finish deformation temperature at 1348 K to 1098 K (1075°C to 825°C) temperature range, the ambient temperature yield stress did not vary significantly, work hardening rate decreased, ultimate tensile strength decreased, and elongation to failure increased. These variations in mechanical properties were correlated to the variations in microstructural parameters (such as ferrite grain size, solid solution concentrations, precipitate number density and dislocation density). Calculations based on the measured microstructural parameters suggested the grain refinement, solid solution strengthening, precipitation strengthening, and work hardening contributed up to 32 pct, up to 48 pct, up to 25 pct, and less than 3 pct to the yield stress, respectively. With a decrease in the finish deformation temperature, both the grain size strengthening and solid solution strengthening increased, the precipitation strengthening decreased, and the work hardening contribution did not vary significantly.

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Section: Tem Study Of Dislocation Structuresupporting

confidence: 87%

Section: A Optical Microscopymentioning

confidence: 99%

See 1 more Smart Citation

Strengthening Mechanisms in Thermomechanically Processed NbTi-Microalloyed Steel

Kostryzhev

Marenych

Killmore³

et al. 2015

Metall Mater Trans A

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“…In respect to the effect of Nb microalloying on high-strength low-alloy steels, many studies have been carried out. [9][10][11][12][13][14][15] An important and widely reported effect in both theoretical and experimental studies is the decrease in the transformation start temperature, thus favoring the formation of low-temperature transformation products such as acicular ferrite and bainite. It also has been demonstrated that Nb precipitates strongly retard austenite recrystallization.…”

Section: Introductionmentioning

confidence: 99%

“…[15,16] Furthermore, Nb additions are known to impart improved strength to these steels through the formation of nanoscale NbC or Nb(NC) precipitates, which retard the movement of dislocations within the grains during deformation. [9][10][11][12][13][14] In this research, we provide the first comprehensive evaluation of the effects of hot rolling and Nb microalloying on the detailed microstructure-property relationships in UCS steels.…”

Section: Introductionmentioning

confidence: 99%

Effect of Nb Microalloying and Hot Rolling on Microstructure and Properties of Ultrathin Cast Strip Steels Produced by the CASTRIP® Process

Xie

Yao

Zhu

et al. 2011

Metall Mater Trans A

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The microstructure and corresponding tensile properties of both plain and Nb-microalloyed grades of ultrathin cast strip (UCS) low alloy steel produced using the CASTRIP Ò process were studied. Both as-cast and hot-rolled strip cast steels with various levels of Nb microalloying were manufactured and investigated in this study. Hot rolling had little effect on the yield strength of Nb microalloyed UCS specimens for a given chemical composition, but resulted in a slightly finer microstructure. The effect of Nb microalloying was significant, and this is attributable to the promotion of finer, tougher austenite transformation products such as bainite and acicular ferrite at the expense of large polygonal ferrite grains. A fine dispersion of Nb solute clusters was observed in all Nb-containing steels following hot rolling, and it is suggested that this also contributes to the observed strengthening.

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Investigation and Application of Nb Microalloying Technology in Seamless Steel Tube with High Performance

Zhang¹,

Wang²,

Sun³

et al. 2015

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

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Microstructural evolution in a new 770MPa hot rolled Nb–Ti microalloyed steel

Cited by 230 publications

References 16 publications

Strengthening Mechanisms in Thermomechanically Processed NbTi-Microalloyed Steel

Strengthening Mechanisms in Thermomechanically Processed NbTi-Microalloyed Steel

Effect of Nb Microalloying and Hot Rolling on Microstructure and Properties of Ultrathin Cast Strip Steels Produced by the CASTRIP® Process

Investigation and Application of Nb Microalloying Technology in Seamless Steel Tube with High Performance

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