Influence of Carbon Content on Toughening in Ultrafine Elongated Grain Structure Steels

Kimura, Yuuji; Inoue, Tatsuo

doi:10.2355/isijinternational.55.1135

Cited by 28 publications

(55 citation statements)

References 19 publications

(43 reference statements)

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“…This is commonly observed in the WTF steels. [7][8][9][10][11] In astempered state, the AF sample has higher σ y and σ B than the non-AF sample. For the AF sample, the WTF with a rolling reduction of 46% causes an increase in the σ y but not in the σ B .…”

Section: Tensile Propertiesmentioning

confidence: 99%

“…4(g)-4(i)) reveals that the non-AF and AF samples have an almost similar distribution of spheroidized carbide particles after the WTF with rolling reductions ranging 46% to 74%. It has been commonly observed that carbide particles grew slightly, becoming more spherical during the WTF at 773 K. [8][9][10][11] Furthermore, strong < 110 > //RD fiber textures are developed through the WTF (Figs. 4(j)-4(l)).…”

Section: Microstructural Characterization and Mechanicalmentioning

confidence: 99%

“…The UFEG structures have been evolved through warm deformation of tempered martensite structures (hereinafter referred to as warm tempforming, WTF), using multi-pass caliber rolling with a rolling reduction of about 80% at 773 K. [7][8][9][10][11] The microstructure evolution during the WTF was observed to depend on variations in the crystallographic orientation and the geometric arrangement of blocks and packets in the tempered martensite. 9,11) As a result, the WTF samples exhibited hierarchical microstructures consisting of "packet bands" and "ultrafine elongated grains (UFEGs)"; the packet bands were evolved through the extension of the packets in the RD and the UFEG structure mainly evolved through the deformation of fine blocks.…”

Section: )mentioning

confidence: 99%

“…On the other hand, in the UFEG structure with a strong < 110 > //RD deformation texture, the microstructural parameters affecting the strength are considered to be its transverse grain size, GND density, and carbide particle distribution. 9,10) A comparison among the changes in these microstructural parameters in Figs. 4 and 5 indicates that the σ y might increase in response to the increase in the GND density and the decrease in the transverse grain size during the WTF with rolling reductions up to 50%.…”

Section: Tensile Propertiesmentioning

confidence: 99%

“…29) As a result, the vE is enhanced through the occurrence of crack arrester-type delamination. When the temperature below which the vE for the WTF samples decrease to the level of its vE US value or less was defined as the delamination finish temperature (T DFT ), 10,11) the respective T DFT values were estimated to be approximately 230 K for the 46%-rolled sample, and 170 K for the 74%-rolled sample. As for the AF samples, the WTF with a rolling reduction of 46% also results in the occurrence of crack arrester-type delamination, and the vE US and T DFT are approximately 75 J at 420 K and 190 K, respectively.…”

Section: Tensile Propertiesmentioning

confidence: 99%

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Combined Effect of Ausforming and Warm Tempforming on the Strength and Toughness of An Ultra-High Strength Steel

Kimura

Inoue

2016

ISIJ International

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Recently, we have reported that ultrafine elongated grain (UFEG) structures with strong < 110 > //rolling direction (RD) fiber textures, which are similar to those in cold drawn steel wires, [4][5][6] are particularly effective in toughening of medium-carbon low-alloy steel bars.7-11) A 0.4C-2Si-1Cr-1Mo steel (mass%) with an UFEG structure had an average yield strength (σ y ) of 1.84 GPa and an average Charpy V-notch absorbed energy (vE) of 226 J at room temperature. 7,9,11) Furthermore, the UFEG structure steels were observed to exhibit an inverse temperature dependence of toughness at subzero temperatures, as a consequence of delamination, in which cracks branched and propagated in the longitudinal direction of impact bars.7-11) The vE of the UFEG structure steels increased as the temperature decreased, in contrast to a ductile-to-brittle transition of conventional ultra-high strength steels. It has also been clarified that the microstructural factors controlling the occurrence A 0.4C-2Cr-1Mo-2Ni steel (in mass%) was austenitized at 1 123 K, followed by ausforming (AF) using multi-pass caliber rolling with a rolling reduction of 74%. The AF samples were subsequently tempered at 773 K and deformed by multi-pass caliber rolling (i.e. warm tempforming, WTF) with a rolling reduction of 46%. Their microstructures and mechanical properties were investigated and compared to those of the quenched and tempered samples (non-AF samples) which were subjected to the sequent WTF with rolling reductions of 46% and 74%. The WTF with rolling reductions ranging 46 to 74% resulted in the strengthening and toughening of the AF and non-AF samples through the evolution of anisotropic and ultrafine grain structures with strong < 110 > //rolling direction (RD) fiber textures. The AF sample demonstrated the faster kinetics of the microstructural changes, i.e. refinement in the transverse grain size and development of highly elongated grains than the non-AF sample. As a result, the AF sample exhibited a better combination of ultra-high strength and toughness than the non-AF sample, when compared at the rolling reduction of 46%. The combined effect of AF and WTF was especially pronounced in the enhancement of toughness resulting from delamination.

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Section: Tensile Propertiesmentioning

confidence: 99%

Section: Microstructural Characterization and Mechanicalmentioning

confidence: 99%

Section: )mentioning

confidence: 99%

Section: Tensile Propertiesmentioning

confidence: 99%

Section: Tensile Propertiesmentioning

confidence: 99%

See 3 more Smart Citations

Combined Effect of Ausforming and Warm Tempforming on the Strength and Toughness of An Ultra-High Strength Steel

Kimura

Inoue

2016

ISIJ International

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An Initial Report on the Structure–Property Relationships of a High‐Strength Low‐Alloy Steel Subjected to Advanced Thermomechanical Processing in Ferrite

Ledermueller

Zhu

et al. 2020

steel research int.

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On delamination toughening of a 14YWT nanostructured ferritic alloy

et al. 2017

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The FCRD NFA-1 is a high strength, irradiation tolerant nanostructured ferritic alloy (NFA) produced by ball milling argon atomized Fe-14Cr-3W-0.35Ti-0.25Y (wt.%) and FeO powders, followed by hot extrusion at 850ºC, and subsequent annealing and crossrolling at 1000ºC. The microstructure of the resulting ≈ 10 mm thick NFA-1 plate is dominated by ultrafine sub-micron pancake shaped grains, and a large population of microcracks lying on planes parallel to the plate faces. Pre-cracked fracture toughness tests in four different orientations (L-T, T-L, L-S and T-S) show stable crack growth by ductile tearing, with peak load KJc from ≈ 88 to 154 MPa√m at ambient temperature. Stable crack tearing persists down to ≈-175°C and is accompanied by extensive delamination due to the propagation of the microcracks. Depending on the specimen orientation, this unusual toughening mechanism is either due to reduction of crack tip stresses in thin ligaments formed by the delaminations (L-T and T-L), or 90° deflection of cracks initially running normal to the delaminations (L-S and T-S), thereby 2 suppressing cleavage in both cases. Understanding the fracture processes in NFA-1 is also important to its irradiation tolerance in nuclear service as well as its fabricability in making defect-free components such as thin-walled tubing.

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Influence of Carbon Content on Toughening in Ultrafine Elongated Grain Structure Steels

Cited by 28 publications

References 19 publications

Combined Effect of Ausforming and Warm Tempforming on the Strength and Toughness of An Ultra-High Strength Steel

Combined Effect of Ausforming and Warm Tempforming on the Strength and Toughness of An Ultra-High Strength Steel

An Initial Report on the Structure–Property Relationships of a High‐Strength Low‐Alloy Steel Subjected to Advanced Thermomechanical Processing in Ferrite

On delamination toughening of a 14YWT nanostructured ferritic alloy

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