Influence of Si on nano sub-structure of cementite lamellae in pearlitic steel wires

Makii, Koichi; Yaguchi, Hiroshi; Kaiso, Masato; Ibaraki, Nobuhiko; Miyamoto, Yasuo; Oki, Yasuhiro

doi:10.1016/s1359-6462(97)00326-6

Cited by 52 publications

(39 citation statements)

References 10 publications

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“…[12][13][14] Although no quantitative data for cementite dissolution during ECAP is at present available, an indirect information can be obtained from the severely cold drawn pearlitic steel wire [15][16][17][18] since (a) the reported maximum drawing strain ϳ5, was comparable to the present ECAP strain, ϳ4, and (b) the morphological evolution of pearlitic cementite during ECAP was similar to that observed in the severely cold drawn pearlitic steel wire. The previous investigations 17,18) reported that 20-50 % of pearlitic cementite was dissolved during cold drawing and resultantly the carbon content in ferrite reached over ϳ4 at%.…”

Section: Formation Of Ufg F/m Dp Steelmentioning

confidence: 90%

Fabrication of Ultrafine Grained Ferrite/Martensite Dual Phase Steel by Severe Plastic Deformation

2005

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Processing of ultrafine grained ferrite/martensite dual phase (UFG F/M DP) steel by equal channel angular pressing (ECAP) and subsequent intercritical annealing was described in detail. Along with strain gradient plasticity concept in which an introduction of a high density of geometrically necessary dislocations attributes to enhance strain hardenability, the aim of the present study was fabrication of UFG F/M DP steel exhibiting extensive strain hardenability, which other UFG materials hardly exhibit, in addition to ultrahigh strength and good uniform elongation. By selecting the optimum ECAP and intercritical annealing conditions, it was possible to fabricate UFG F/M DP steel in which isolated UFG martensite islands were uniformly embedded into UFG ferrite matrix. The formation of such a unique microstructure under the present processing conditions was discussed in terms of microstructural evolution during ECAP. Room temperature tensile properties of UFG F/M DP steel were superior to those of coarse grained counterpart. More importantly, in spite of an UFG structure, the present UFG F/M DP steel exhibited extensive strain hardenability from the onset of plastic deformation in association with grain size independent strain gradient plasticity, unlike other UFG materials.KEY WORDS: ultrafine grain; dual phase steel; equal channel angular pressing; microstructure; tensile properties.cessing step in order to maintain UFG structure since intercritical annealing is undertaken at high temperatures belonging to ferrite/austenite two phases region. So, in this section, each processing step is described in detail. MaterialA plain carbon-manganese steel (Fe-0.15C-0.25Si-1.1Mn (in mass%)) was used in the present investigation. It was prepared as a 50 kg ingot by a vacuum induction melting. The ingot was homogenized at 1 250°C for 1 h and size-rolled to the plate of 50 mm thickness and 150 mm width. The rolled plate was austenitized at 1 200°C for 1 h and then air-cooled. Equal Channel Angular PressingECAP was performed on the cylindrical samples of 130 mm length and 10 mm diameter which were machined from the rolled plate. The outer curvature and inner contact angles of intersection between two channels of the present ECA pressing die were 20°and 90°respectively so that it yielded an effective strain of ϳ1 by a single pass. Each sample was subjected to 4 passes, i.e. total accumulated effective strain of ϳ4, since structural refinement became saturated at this level of ECAP strain. During ECAP, the sample was rotated 180°around its longitudinal axis between the passages, i.e. route C. Route C was selected by the following considerations [6][7][8] : (a) it restores the shape of the original segment at even number passes and thereby a nearly equiaxed UFG structure can be obtained, and (b) it produces higher effective strain without changing the shape at even number passes than other ECAP routes due to repetitive shearing on the same plane. ECAP was conducted at 500°C with a ram speed of 2 mm/s. The relatively high ECAP tem...

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Section: Formation Of Ufg F/m Dp Steelmentioning

confidence: 90%

Fabrication of Ultrafine Grained Ferrite/Martensite Dual Phase Steel by Severe Plastic Deformation

2005

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“…The presence of such fine cementite crystals was previously reported in heavily drawn wires. [6][7][8] It is clear that microstructure change in cementite lamellae similar to the case of drawn wires also occurs during cold rolling. It is expected that cementite in FL, more heavily deformed than in CLS, also shows a nanocrystalline structure.…”

Section: Pearlitic Microstructure Formed After Isothermalmentioning

confidence: 96%

“…Most recently, Nishida et al 5) proposed that the strength of deformed pearlite could be described by the rule of mixture for the strength of work-hardened ferrite and that of undeformed cementite. However, it is recently pointed out that microscopic change of cementite to nanocrystals or amorphous occurs in heavy deformation by wire drawing, [6][7][8] implying that work hardening of pearlite may not be simply explained by the refining of interlamellar spacing.…”

Section: Introductionmentioning

confidence: 99%

Deformation Microstructure and Tensile Strength of Cold Rolled Pearlitic Steel Sheets

et al. 2000

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The deformation microstructure produced by heavy cold rolling (from 70 % to 95 % reduction) of pearlitic structure with various amounts of rolling and the tensile strength of the cold rolled sheets were studied in the plain carbon steels with various carbon contents (0.6, 0.76, and 1.0 mass%C). The deformation microstructure was classified into the following three types; 1) Irregularly Bent Lamella (IBL): lamellae originally inclined with large angles to the rolling plane and irregularly bent after deformation, 2) Coarse Lamella with Shear band (CLS) : the rhomboidal blocks of weakly deformed lamellae bounded by shear band, 3) Fine Lamella (FL): heavily deformed lamellae aligned parallel to the rolling direction with fine interlamellar spacings. As rolling reduction increases, the proportion of FL increases.The tensile strength of cold rolled specimens increases with rolling reduction. Work hardening with respect to true strain by cold rolling is similar to that obtained by wire drawing. After 92 % cold rolling of 1.0 mass%C steel, the tensile strength over 2 500 MPa was achieved.

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“…However, recent TEM or AP-FIM (atom probe field ion microscopy) studies reported that q lamellae change to nanocrystals and the dissolution of q in a occurs during heavy cold drawing. [16][17][18][19][20] Such dissolution of q during cold drawing was also pointed out by means of Mössbauer spectroscopy. 3,[21][22][23] In fact, the present authors also observed the nanocrystalline q formed by heavy cold rolling.…”

Section: The Strengthening Of Pearlite By Cold Rollingmentioning

confidence: 74%

Effect of Mn and Si Addition on Microstructure and Tensile Properties of Cold-rolled and Annealed Pearlite in Eutectoid Fe-C Alloys

Maki

2004

ISIJ International

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The microstructures and tensile properties of cold-rolled and annealed pearlite in Fe-0.8mass%C alloys with various contents of Mn and Si were investigated. With the addition of Mn and Si, the tensile strength (TS) and yield strength (YS) of cold-rolled and annealed pearlite were vastly improved, but its effect on ductility of the cold-rolled pearlite is negligible. The addition of Si is quite effective in improving the ductility of coldrolled and annealed pearlite, especially when the strength is at a higher level, i.e., lower annealing temperature or shorter annealing period. The optimal tensile properties in the alloys with Mn or Si were obtained after annealing at 723 K for short annealing periods (30 to 120 s). The combined addition of Mn and Si is more effective in improving the tensile properties of cold-rolled and annealed pearlite.KEY WORDS: pearlite; eutectoid steel; cold working; annealing; ultrafine-grained microstructure; mechanical property. Table 1. Chemical compositions of the alloys used (mass%).Philips CM200). The specimens for SEM observation were etched with 1 % nital after mechanical polishing. Thin foils for TEM observation were cut by an electrode discharge machine to 0.5 mmϫ0.5 mmϫ3.0 mm, mechanically thinned to 50 mm thick, and electropolished by a twin-jet polisher with 5 % perchloric acid and acetic acid solution at 36 V and 284 K.ISP in each as-transformed specimen was determined by using the TEM micrographs on which q lamellae interface was parallel to the incident beam. The q particle sizes in the specimens annealed at 923 K were determined by SEM. Using the Image analysis software (AnalySIS), which digitizes an image from the photograph, the stained carbides were identified based on gray level and separated for analysis. The area (A) of a 2-dimentional section at the polished plane was measured for each particle, and converted to an equivalent circle diameter (ECD; ϭ(4 A/p) 1/2 ) of the particle. 10) At least, four micrographs were taken with a magnification from 3 000 to 20 000 for each specimen. The total number of measured particles ranged from approximately 500 to 1 300, depending on materials and annealing periods at 923 K.The XRD (X-ray diffraction) experiment was carried out on a Philips PW1078/50 X-ray diffractometer. The tube voltage and current were 40 kV and 40 mA, respectively. The tube anode was Cu K a1 (lϭ0.15406 nm), and the receiving slit was 2 mm. The precise position of each peak was determined with the method "width of the curve at half ".Tensile tests were performed at the initial strain rate of 2ϫ10 Ϫ3 /s for the specimens of which gage size was 2.5 mm w ϫ8.5 mm l ϫ0.5 mm t and longitudinal direction was parallel to the rolling direction (RD). Results Microstructure and Tensile Properties of theAs-transformed Pearlite After austenitization at 1 123 K for 1.8 ks and subsequent isothermal transformation at 873 K for 0.6 ks, fully pearlitic structures contained mostly of lamellar cementite were obtained. The effect of Mn and Si addition on ISPs and tensile propert...

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Influence of Si on nano sub-structure of cementite lamellae in pearlitic steel wires

Cited by 52 publications

References 10 publications

Fabrication of Ultrafine Grained Ferrite/Martensite Dual Phase Steel by Severe Plastic Deformation

Fabrication of Ultrafine Grained Ferrite/Martensite Dual Phase Steel by Severe Plastic Deformation

Deformation Microstructure and Tensile Strength of Cold Rolled Pearlitic Steel Sheets

Effect of Mn and Si Addition on Microstructure and Tensile Properties of Cold-rolled and Annealed Pearlite in Eutectoid Fe-C Alloys

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