TY - JOUR
T1 - Increasing fatigue life of 09mn2si steel by helical rolling
T2 - Theoretical–experimental study on governing role of grain boundaries
AU - Panin, Sergey
AU - Vlasov, Ilya
AU - Maksimov, Pavel
AU - Moiseenko, Dmitry
AU - Maruschak, Pavlo
AU - Yakovlev, Alexander
AU - Schmauder, Siegfried
AU - Berto, Filippo
N1 - Funding Information:
Funding: This study has been funded in the frame of the government research program (ISPMS SB RAS, Projects III.23.1.1 and III.23.1.3—????) as well as partially supported by RFBR Grant 18-08-00516 (Section ??). Financial support of RF President Council Grant for the support of leading research schools NSh-2718.2020.8 (Section ??) is also acknowledged. Fatigue tests were carried out at the National Research Tomsk Polytechnic University, within the framework of the Competitiveness Enhancement Program of Tomsk Polytechnic University.
Publisher Copyright:
© 2020 by the authors. Licensee MDPI, Basel, Switzerland.
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2020/10/2
Y1 - 2020/10/2
N2 - The structure and mechanical properties of the 09Mn2Si high-strength low-alloyed steel after the five-stage helical rolling (HR) were studied. It was revealed that the fine-grained structure had been formed in the surface layer ≈ 1 mm deep as a result of severe plastic strains. In the lower layers, the “lamellar” structure had been formed, which consisted of thin elongated ferrite grains oriented in the HR direction. It was shown that the five-stage HR resulted in the increase in the steel fatigue life by more than 3.5 times under cyclic tension. The highest values of the number of cycles before failure were obtained for the samples cut from the bar core. It was demonstrated that the degree of the elastic energy dissipation in the steel samples under loading directly depended on the area of the grain boundaries as well as on the grain shapes. The fine-grained structure possessed the maximum value of the average torsional energy among all the studied samples, which caused the local material structure transformation and the decrease in the elastic energy level. This improved the crack resistance under the cyclic mechanical loading. The effect of the accumulation of the rotational strain modes at the grain boundaries was discovered, which caused the local structure transformation at the boundary zones. In the fine-grained structure, the formation of grain conglomerates was observed, which increased the values of the specific modulus of the moment of force. This could be mutually compensated due to the small sizes of grains. At the same time, the coarse-grained structures were characterized by the presence of the small number of grains with a high level of the moments of forces at their boundaries. They could result in trans-crystalline cracking.
AB - The structure and mechanical properties of the 09Mn2Si high-strength low-alloyed steel after the five-stage helical rolling (HR) were studied. It was revealed that the fine-grained structure had been formed in the surface layer ≈ 1 mm deep as a result of severe plastic strains. In the lower layers, the “lamellar” structure had been formed, which consisted of thin elongated ferrite grains oriented in the HR direction. It was shown that the five-stage HR resulted in the increase in the steel fatigue life by more than 3.5 times under cyclic tension. The highest values of the number of cycles before failure were obtained for the samples cut from the bar core. It was demonstrated that the degree of the elastic energy dissipation in the steel samples under loading directly depended on the area of the grain boundaries as well as on the grain shapes. The fine-grained structure possessed the maximum value of the average torsional energy among all the studied samples, which caused the local material structure transformation and the decrease in the elastic energy level. This improved the crack resistance under the cyclic mechanical loading. The effect of the accumulation of the rotational strain modes at the grain boundaries was discovered, which caused the local structure transformation at the boundary zones. In the fine-grained structure, the formation of grain conglomerates was observed, which increased the values of the specific modulus of the moment of force. This could be mutually compensated due to the small sizes of grains. At the same time, the coarse-grained structures were characterized by the presence of the small number of grains with a high level of the moments of forces at their boundaries. They could result in trans-crystalline cracking.
KW - Cellular automata
KW - Cracking
KW - Fatigue
KW - Grain boundary
KW - Grain size
KW - Helical rolling
KW - Heterogeneous materials
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U2 - 10.3390/ma13204531
DO - 10.3390/ma13204531
M3 - Article
AN - SCOPUS:85093936732
VL - 13
SP - 1
EP - 29
JO - Materials
JF - Materials
SN - 1996-1944
IS - 20
M1 - 4531
ER -