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| Microstructure evolution of Fe-33Mn-4Si steel during low-cycle fatigue deformation |
Qidi SUN1,2, Weitao YANG1,2, Qingguo HAO1,2, Xiaohu GUAN3, Bin ZHANG4, Qi YANG1,2,*( ) |
1 Shanghai Research Institute of Materials, Shanghai 200437, China
2 Shanghai Key Laboratory of Engineering Materials Application and Evaluation, Shanghai 200437, China
3 School of Metallurgical Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
4 Analytical Applications Center, Shimadzu (China) Co., Ltd.Shanghai Branch, Shanghai 200233, China |
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Abstract The microstructure evolution and mechanical behavior of an Fe-33Mn-4Si alloy steel under low-cycle fatigue deformation were investigated by using the X-ray diffraction and electron backscatter diffraction techniques.Results show that the experimental steel has an initial microstructure consisting of austenite and thermally induced ε-martensite. The initial microstructure remarkably affects the low-cycle fatigue property of the experimental steel through influencing the ε-martensitic transformation during deformation. At the early stage of fatigue deformation (first 100 deformation cycles), with increasing deformation cycles, a rapid increase in the volume fraction of ε-martensite and the frequency of the intersection of ε-martensite with different variants result in a quick rise in cyclic average peak stress and work hardening degree. With the continuation of cyclic deformation up to fatigue fracture, the ε-martensite becomes the dominant constituent phase in the deformation microstructure, and the volume fraction of ε-martensite and the frequency of the intersection of ε-martensite increase at an appreciably slower rate, thereafter significantly slowing the increase in cyclic average peak stress and work hardening degree.
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Received: 14 June 2021
Published: 18 April 2022
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Corresponding Authors:
Qi YANG
E-mail: m1866733474@163.com
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Schematic illustration of low-cycle fatigue test sample
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LCF property hysteresis loops(a) and variation of the average peak stress(b), work hardening degree(c), and plastic and elastic strain range(d) with fatigue cycles of the experimental steel
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Initial microstructure of the experimental steel
(a)phase map; (b)XRD pattern
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fig. 3(a)
(a)inverse pole figure (IPF) map; (b)phase map; (c)image quality (IQ) map; (d)Kernel average misorientation (KAM) map; (e)indication of {111}γ planes corresponding to ε-martensitic variants marked in fig.(a), (b)
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Fine microstructure in the boxed area shown in fig. 3(a)
(a)inverse pole figure (IPF) map; (b)phase map; (c)image quality (IQ) map; (d)Kernel average misorientation (KAM) map; (e)indication of {111}γ planes corresponding to ε-martensitic variants marked in fig.(a), (b)
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Phase constitution of the experimental steel
(a)XRD patterns after different fatigue cycles; (b)volume fraction of ε-martensite
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Deformation microstructures of the experimental steel (the horizontal direction in (a)-(f) is parallel to the loading direction)
(a), (b)phase map and KAM map of the specimen deformed to 100 cycles; (c), (d)phase map and KAM map of the specimen deformed to 1000 cycles; (e), (f)phase map and KAM map of the fatigue failed specimen; (g)misorientation angle distribution of ε-martensite phase; (h)KAM distribution of ε-martensite phase
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fig. 6(f) (the horizontal direction is parallel to the loading direction)
(a)grain Ⅰ; (b)grain Ⅱ; (c)grain Ⅲ; (d)-(f) is showing {111}γ planes in the selected grains (the solid black lines denote existing ε-martensite variants, the dashed black lines denote non-existing ε-martensite variants, and the green line represents the twin plane); (1)IQ map; (2)phase map; (3)IPF map
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Fine microstructure in selected grains shown in fig. 6(f) (the horizontal direction is parallel to the loading direction)
(a)grain Ⅰ; (b)grain Ⅱ; (c)grain Ⅲ; (d)-(f) is showing {111}γ planes in the selected grains (the solid black lines denote existing ε-martensite variants, the dashed black lines denote non-existing ε-martensite variants, and the green line represents the twin plane); (1)IQ map; (2)phase map; (3)IPF map
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2022, Vol. 50 
