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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.


TEM bright-field images of the precipitates for the BA low-carbon steels.
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fig7: TEM bright-field images of the precipitates for the BA low-carbon steels.

Mentions: Two TEM bright-field images of the precipitates for the BA steels are shown in Fig. 7 ▶. Most of the precipitates in the ferrite matrix were identified by EDS analysis as BN precipitates which have a nucleus of MnS or CuS. The nucleus size is mainly in the range 100–500 Å, although some precipitates contain a large nucleus of up to 5000 Å. In addition, BN precipitates have grown in particular on the surface of the MnS or CuS nuclei. Thus, in the BA steels, the shapes of the precipitates are either a core–shell structured sphere or an ellipsoidal shape, such as MnS and CuS precipitates surrounded by BN layers. The shapes of precipitates like MnS and CuS are either spherical or ellipsoidal in the BF steels.


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)

TEM bright-field images of the precipitates for the BA low-carbon steels.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig7: TEM bright-field images of the precipitates for the BA low-carbon steels.
Mentions: Two TEM bright-field images of the precipitates for the BA steels are shown in Fig. 7 ▶. Most of the precipitates in the ferrite matrix were identified by EDS analysis as BN precipitates which have a nucleus of MnS or CuS. The nucleus size is mainly in the range 100–500 Å, although some precipitates contain a large nucleus of up to 5000 Å. In addition, BN precipitates have grown in particular on the surface of the MnS or CuS nuclei. Thus, in the BA steels, the shapes of the precipitates are either a core–shell structured sphere or an ellipsoidal shape, such as MnS and CuS precipitates surrounded by BN layers. The shapes of precipitates like MnS and CuS are either spherical or ellipsoidal in the BF steels.

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.