TY - JOUR
T1 - Delamination effect on impact properties of ultrafine-grained low-carbon steel processed by warm caliber rolling
AU - Inoue, Tadanobu
AU - Yin, Fuxing
AU - Kimura, Yuuji
AU - Tsuzaki, Kaneaki
AU - Ochiai, Shojiro
N1 - Funding Information:
The authors thank S. Kuroda, Y. Taniuchi, and K. Nakazato for materials processing and Ms. E. Motoki and T. Tanaka for their experimental assistance in the microstructural observations. This study was carried out on the basis of seminal research of the Ultra-Steel Project, which began in April 1997 and was completed in March 2006 at the National Institute for Materials Science, and was supported, in part, by KAKENHI, a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, No. 20360339 (April 2008 through March 2010).
PY - 2010/2
Y1 - 2010/2
N2 - Bulk ultrafine-grained (UFG) low-carbon steel bars were produced by caliber rolling, and the impact and tensile properties were investigated. Initial samples with two different microstructures, ferrite-pearlite and martensite (or bainite), were prepared and then caliber rolling was conducted at 500 °C. The microstructures in the rolled bars consisted of an elongated UFG structure with a strong α-fiber texture. The rolled bar consisting of spheroidal cementite particles that distributed uniformly in the elongated ferrite matrix of transverse grain sizes 0.8 to 1.0 μm exhibited the best strength-ductility balance and impact properties. Although the yield strength in the rolled bar increased 2.4 times by grain refinement, the upper-shelf energy did not change, and its value was maintained from 100 °C to -40 °C. In the rolled bars, cracks during an impact test branched parallel to the longitudinal direction of the test samples as temperatures decreased. Delamination caused by such crack branching appeared, remarkably, near the ductile-to-brittle transition temperature (DBTT). The effect of delamination on the impact properties was associated with crack propagation on the basis of the microstructural features in the rolled bars. In conclusion, the strength-toughness balance is improved by refining crystal grains and controlling their shape and orientation; in addition, delamination effectively enhances the low-temperature toughness.
AB - Bulk ultrafine-grained (UFG) low-carbon steel bars were produced by caliber rolling, and the impact and tensile properties were investigated. Initial samples with two different microstructures, ferrite-pearlite and martensite (or bainite), were prepared and then caliber rolling was conducted at 500 °C. The microstructures in the rolled bars consisted of an elongated UFG structure with a strong α-fiber texture. The rolled bar consisting of spheroidal cementite particles that distributed uniformly in the elongated ferrite matrix of transverse grain sizes 0.8 to 1.0 μm exhibited the best strength-ductility balance and impact properties. Although the yield strength in the rolled bar increased 2.4 times by grain refinement, the upper-shelf energy did not change, and its value was maintained from 100 °C to -40 °C. In the rolled bars, cracks during an impact test branched parallel to the longitudinal direction of the test samples as temperatures decreased. Delamination caused by such crack branching appeared, remarkably, near the ductile-to-brittle transition temperature (DBTT). The effect of delamination on the impact properties was associated with crack propagation on the basis of the microstructural features in the rolled bars. In conclusion, the strength-toughness balance is improved by refining crystal grains and controlling their shape and orientation; in addition, delamination effectively enhances the low-temperature toughness.
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U2 - 10.1007/s11661-009-0093-x
DO - 10.1007/s11661-009-0093-x
M3 - Article
AN - SCOPUS:77949275779
SN - 1073-5623
VL - 41
SP - 341
EP - 355
JO - Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
JF - Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
IS - 2
ER -