Work Hardening and Microstructural Development during High-Pressure Torsion in Pure Iron

Hosokawa, Akihide; Seiichiro,; Tsuchiya, Koichi

doi:10.2320/matertrans.m2013462

Cited by 17 publications

(11 citation statements)

References 27 publications

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“…In fact, a cooling rate exceeding 35,000 • C/s could lead to martensitic transformation even in iron-based alloys containing less than 0.002% • C [28], and the cooling rate during L-PBF processing can exceed 10 6 • C/s [29]. Thus, the processing-induced combination of high internal stresses, a relatively fine grain structure (10-15 µm) and small quantities of martensite results in an increased material strength, but this increase occurs at the expense of a significant reduction in ductility [30]. A comparison of the L-PBF-built specimens with their pressed-and-sintered counterparts reveals that the YS and UTS values of the L-PBF specimens are 12-15% higher and their elongations to failure are more than double those of the P-S specimens (Figure 11), given their higher density and stronger metallurgical bonding (melting versus sintering).…”

Section: Tensile Properties Microstructure and Wall Thicknessmentioning

confidence: 99%

Laser Powder Bed Fusion of Water-Atomized Iron-Based Powders: Process Optimization

Letenneur

Braïlovski

Kreitcberg

et al. 2017

JMMP

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Abstract:The laser powder bed fusion (L-PBF) technology was adapted for use with non-spherical economical water-atomized iron powders. A simplified numerical and experimental modeling approach was applied to determine-in a first approximation-the operation window for the selected powder in terms of laser power, scanning speed, hatching space, and layer thickness. The operation window, delimited by a build rate ranging from 4 to 25 cm 3 /h, and a volumetric energy density ranging from 50 to 190 J/mm 3 , was subsequently optimized to improve the density, the mechanical properties, and the surface roughness of the manufactured specimens. Standard L-PBF-built specimens were subjected to microstructural (porosity, grain size) and metrological (accuracy, shrinkage, minimum wall thickness, surface roughness) analyses and mechanical testing (three-point bending and tensile tests). The results of the microstructural, metrological and mechanical characterizations of the L-PBF-built specimens subjected to stress relieve annealing and hot isostatic pressing were then compared with those obtained with conventional pressing-sintering technology. Finally, by using an energy density of 70 J/mm 3 and a build rate of 9 cm 3 /h, it was possible to manufacture 99.8%-dense specimens with an ultimate strength of 330 MPa and an elongation to failure of 30%, despite the relatively poor circularity of the powder used.

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Section: Tensile Properties Microstructure and Wall Thicknessmentioning

confidence: 99%

Laser Powder Bed Fusion of Water-Atomized Iron-Based Powders: Process Optimization

Letenneur

Braïlovski

Kreitcberg

et al. 2017

JMMP

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“…It has recently been reported that the surface finished by FIB yields a better image quality (IQ) in EBSD measurements. 9) Microvickers hardness was also measured from the well polished cross sections, whereby the radial position of the individual indentations were measured to quantify the local strain. Magnetization curves were measured using vibrating sample magnetometer (VSM) and partially using superconducting quantum interference device (SQUID).…”

Section: Methodsmentioning

confidence: 99%

“…7. Our previous work reported that a weak deformation texture is formed by HPT for pure iron, 9) whereby h110i becomes parallel to the disc normal. It is interesting to note that FeCo (B2) also resulted in a similar deformation texture.…”

Section: *2mentioning

confidence: 99%

Micostructure and Magnetic Properties in Nanostructured Fe and Fe-Based Intermetallics Produced by High-Pressure Torsion

Hosokawa

Ohtsuka

et al. 2014

Mater. Trans.

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The microstructure and magnetic properties of nanostructured pure iron, FeCo and FeNi 3 produced by high-pressure torsion (HPT) were investigated. Electron backscattered diffraction (EBSD) technique was used to study the evolutions in microstructure and crystallographic texture during HPT, revealing that a weak deformation texture with an orientation of h110i bcc being parallel to the disc normal for pure iron and FeCo while h110i fcc was found to be parallel to the hoop direction of the HPT disc in FeNi 3 . The grain size of the HPTed materials was characterized by means of EBSD and transmission electron microscopy (TEM), and its influence on the coercivity was investigated. The other highlight of this paper is the use of a focused ion beam (FIB)-SEM dual beam instrument. This enabled us to obtain quite high image quality (IQ) values for the EBSD measurements even for the highly deformed microstructure in the current ferromagnetic intermetallics. Keywords: bulk nanostructured metals, severe plastic deformation, electron backscattered diffraction (EBSD), magnetic materials, coercivity, focused ion beam-scanning electron microscope (FIB-SEM)

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“…According to X-ray studies in pure iron, most of the elements at the stage of the mixed structure has been established to possess an {101} orientation, whereas the material at the stage of the SMC structure transits into a textureless state [5]. Data received by means of electron back-scatter diffraction (EBSD) give an evidence that the final texture obtained by HPT is {110} being parallel to the disc [12].…”

Section: Introductionmentioning

confidence: 99%

“…But only in a few of them the change of the crystallographic texture is analyzed [5,10,12]. According to X-ray studies in pure iron, most of the elements at the stage of the mixed structure has been established to possess an {101} orientation, whereas the material at the stage of the SMC structure transits into a textureless state [5].…”

Section: Introductionmentioning

confidence: 99%

Effect of microcrystallites formed by deformation on the growth and orientation of grains during recrystallization of iron

Воронова¹,

Degtyarev²,

Чащухина³

et al. 2017

LoM

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Changes of an ultradispersed structure in deformed iron after annealing have been studied. Ultradispersed structures of two different types, cellular and submicrocrystalline (SMC) ones, have been formed in iron by high pressure torsion deformation. The effect of the deformation structure type on the temperature of recrystallization onset, the size of recrystallized grains, and the recrystallization texture has been explored. A comparison of recrystallization of the initial cellular and SMC structures should be made to determine the role of microcrystallites. The recrystallization temperature of iron with an SMC structure is 200 to 250°С lower than that of iron with a cellular structure because of the presence of microcrystallites, which are ready recrystallization nuclei. The recrystallization (annealing at 750°C, 1h) of the cellular structure results in the formation of a coarse-grained structure with an average recrystallized grain size that is by an order of magnitude larger than that after the same annealing of the SMC structure (5 and 180 μm, respectively). The significantly different feature of the SMC structure in contrast to the cellular one is the annealing-assisted formation of a <110> recrystallization texture in it, whereas the annealing of iron with the cellular structure does not cause the formation of a recrystallization macrotexture. An increase in the sharpness of the recrystallization texture correlates with a decrease in the average grain-boundary misorientation angle.

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Work Hardening and Microstructural Development during High-Pressure Torsion in Pure Iron

Cited by 17 publications

References 27 publications

Laser Powder Bed Fusion of Water-Atomized Iron-Based Powders: Process Optimization

Laser Powder Bed Fusion of Water-Atomized Iron-Based Powders: Process Optimization

Micostructure and Magnetic Properties in Nanostructured Fe and Fe-Based Intermetallics Produced by High-Pressure Torsion

Effect of microcrystallites formed by deformation on the growth and orientation of grains during recrystallization of iron

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