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Study of the effect of nano-sized precipitates on the mechanical properties of boron-added low-carbon steels by neutron scattering techniques.

Seong BS, Cho YR, Shin EJ, Kim SI, Choi SH, Kim HR, Kim YJ - J Appl Crystallogr (2008)

Bottom Line: In the BA steels, the number of boron precipitates, such as BN, Fe(3)(C,B) and MnS, surrounded by BN layers increased drastically at higher hot-rolling temperatures.The volume fraction of the fine precipitates of the BA steels was higher than that of the BF steels; this difference is related to the rapid growth of the BN layers on the MnS and CuS precipitates.Boron addition to low-carbon steels resulted in a reduction in strength and an improvement in elongation; this behaviour is related to the reduction of the solute carbon and the nitrogen contents in the ferrite matrix caused by the precipitation of BN, as well by the increase in the volume fraction of the cementites.

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ABSTRACT
Small-angle neutron scattering (SANS) and neutron powder diffraction (ND) techniques were used to study quantitatively the effect of nano-sized precipitates and boron addition on the mechanical properties of low-carbon steels. SANS was used to evaluate nano-sized precipitates, smaller than about 600 A in diameter, and ND was used to determine the weight fraction of the cementite precipitates. Fine core-shell structured spherical precipitates with an average radius of ~50 A, such as MnS and/or CuS, surrounded by BN layers were observed in the boron-added (BA) low-carbon steels; fine spherical precipitates with an average radius of ~48 A were mainly observed in the boron-free (BF) low-carbon steels. In the BA steels, the number of boron precipitates, such as BN, Fe(3)(C,B) and MnS, surrounded by BN layers increased drastically at higher hot-rolling temperatures. The volume fraction of the fine precipitates of the BA steels was higher than that of the BF steels; this difference is related to the rapid growth of the BN layers on the MnS and CuS precipitates. Boron addition to low-carbon steels resulted in a reduction in strength and an improvement in elongation; this behaviour is related to the reduction of the solute carbon and the nitrogen contents in the ferrite matrix caused by the precipitation of BN, as well by the increase in the volume fraction of the cementites.

No MeSH data available.


Measured nuclear SANS data and fitted results. (a) BA, FET 1151 K, (b) BA, FET 1208 K, (c) BF, FET 1148 K and (d) BF, FET 1185 K.
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fig10: Measured nuclear SANS data and fitted results. (a) BA, FET 1151 K, (b) BA, FET 1208 K, (c) BF, FET 1148 K and (d) BF, FET 1185 K.

Mentions: Some examples of the measured nuclear SANS spectra and the fitted spectra for the BA and BF steels are shown in Fig. 10 ▶. Open circles correspond to the observed intensities and the solid line represents the fitted ones. Dashed lines are backgrounds. Even though the spectra are very weak and have poor statistics above 0.05 Å−1, the fitted spectra are in good agreement with the measured ones. As model fitting results, the Porod constants A p and the bkg values were obtained as almost same values, 1.013 × 1025 cm−5 and 0.0146 cm−1, respectively, for all samples. This means that all samples have similar large precipitates with almost the same compositions of the precipitates and interface area between the matrix and precipitates.


Study of the effect of nano-sized precipitates on the mechanical properties of boron-added low-carbon steels by neutron scattering techniques.

Seong BS, Cho YR, Shin EJ, Kim SI, Choi SH, Kim HR, Kim YJ - J Appl Crystallogr (2008)

Measured nuclear SANS data and fitted results. (a) BA, FET 1151 K, (b) BA, FET 1208 K, (c) BF, FET 1148 K and (d) BF, FET 1185 K.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2553556&req=5

fig10: Measured nuclear SANS data and fitted results. (a) BA, FET 1151 K, (b) BA, FET 1208 K, (c) BF, FET 1148 K and (d) BF, FET 1185 K.
Mentions: Some examples of the measured nuclear SANS spectra and the fitted spectra for the BA and BF steels are shown in Fig. 10 ▶. Open circles correspond to the observed intensities and the solid line represents the fitted ones. Dashed lines are backgrounds. Even though the spectra are very weak and have poor statistics above 0.05 Å−1, the fitted spectra are in good agreement with the measured ones. As model fitting results, the Porod constants A p and the bkg values were obtained as almost same values, 1.013 × 1025 cm−5 and 0.0146 cm−1, respectively, for all samples. This means that all samples have similar large precipitates with almost the same compositions of the precipitates and interface area between the matrix and precipitates.

Bottom Line: In the BA steels, the number of boron precipitates, such as BN, Fe(3)(C,B) and MnS, surrounded by BN layers increased drastically at higher hot-rolling temperatures.The volume fraction of the fine precipitates of the BA steels was higher than that of the BF steels; this difference is related to the rapid growth of the BN layers on the MnS and CuS precipitates.Boron addition to low-carbon steels resulted in a reduction in strength and an improvement in elongation; this behaviour is related to the reduction of the solute carbon and the nitrogen contents in the ferrite matrix caused by the precipitation of BN, as well by the increase in the volume fraction of the cementites.

View Article: PubMed Central - HTML - PubMed

ABSTRACT
Small-angle neutron scattering (SANS) and neutron powder diffraction (ND) techniques were used to study quantitatively the effect of nano-sized precipitates and boron addition on the mechanical properties of low-carbon steels. SANS was used to evaluate nano-sized precipitates, smaller than about 600 A in diameter, and ND was used to determine the weight fraction of the cementite precipitates. Fine core-shell structured spherical precipitates with an average radius of ~50 A, such as MnS and/or CuS, surrounded by BN layers were observed in the boron-added (BA) low-carbon steels; fine spherical precipitates with an average radius of ~48 A were mainly observed in the boron-free (BF) low-carbon steels. In the BA steels, the number of boron precipitates, such as BN, Fe(3)(C,B) and MnS, surrounded by BN layers increased drastically at higher hot-rolling temperatures. The volume fraction of the fine precipitates of the BA steels was higher than that of the BF steels; this difference is related to the rapid growth of the BN layers on the MnS and CuS precipitates. Boron addition to low-carbon steels resulted in a reduction in strength and an improvement in elongation; this behaviour is related to the reduction of the solute carbon and the nitrogen contents in the ferrite matrix caused by the precipitation of BN, as well by the increase in the volume fraction of the cementites.

No MeSH data available.