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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 cross section for low-carbon steels: (a) BA steels and (b) BF steels.
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fig9: Measured nuclear SANS cross section for low-carbon steels: (a) BA steels and (b) BF steels.

Mentions: The one-dimensional nuclear SANS cross sections extracted from the two-dimensional SANS patterns for (a) the BA and (b) the BF steels for different hot-rolling temperatures are shown in Fig. 9 ▶. The intensities of the SANS spectra show a small difference over all the measured Q ranges in the BA steels according to the hot-rolling temperature, whereas the intensities do not show a significant difference in the BF steels. However, in both the BA and the BF steels, the intensities follow the law ∼A p Q −4 for Q < 0.02 Å−1, known as Porod (1982 ▶) scattering. A p is proportional to the total area of the interface between the precipitates and the matrix. The intensities in the Q range 0.02–0.06 Å−1 for all the samples show a clear difference due to the polydispersed precipitates. The intensities for Q > 0.11 Å−1 become close to the background level.


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 cross section for low-carbon steels: (a) BA steels and (b) BF steels.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig9: Measured nuclear SANS cross section for low-carbon steels: (a) BA steels and (b) BF steels.
Mentions: The one-dimensional nuclear SANS cross sections extracted from the two-dimensional SANS patterns for (a) the BA and (b) the BF steels for different hot-rolling temperatures are shown in Fig. 9 ▶. The intensities of the SANS spectra show a small difference over all the measured Q ranges in the BA steels according to the hot-rolling temperature, whereas the intensities do not show a significant difference in the BF steels. However, in both the BA and the BF steels, the intensities follow the law ∼A p Q −4 for Q < 0.02 Å−1, known as Porod (1982 ▶) scattering. A p is proportional to the total area of the interface between the precipitates and the matrix. The intensities in the Q range 0.02–0.06 Å−1 for all the samples show a clear difference due to the polydispersed precipitates. The intensities for Q > 0.11 Å−1 become close to the background level.

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.