Search results for: Tadashi Furuhara

Items from 1 to 20 out of 46 results

article

Effect of Ferrite/Martensite Phase Size on Tensile Behavior of Dual-Phase Steels with Nano-Precipitation of Vanadium Carbides

Elango Chandiran, Yu Sato, Naoya Kamikawa, Goro Miyamoto, more

Metallurgical and Materials Transactions A > 2019 > 50 > 9 > 4111-4126

This study investigates the effect of ferrite/martensite phase size and dispersion of nano-precipitates in ferrite on strength, ductility, and fracture behavior of dual-phase (DP) steels. Dispersion of nano-precipitates in ferrite improves the strength with keeping sufficient uniform elongation and post-uniform elongation, while decrease in ferrite/martensite phase size has a little effect on the...

article

Strengthening Mechanisms in Ultrafine-Grained and Sub-grained High-Purity Aluminum

Naoya Kamikawa, Taisuke Hirochi, Tadashi Furuhara

Metallurgical and Materials Transactions A > 2019 > 50 > 1 > 234-248

This study investigates the effect of grain/sub-grain size, boundary misorientation, and dislocation density on mechanical properties of nanostructured aluminum. A fully recrystallized high-purity aluminum was deformed to different strains from low to ultrahigh strains by a combination of conventional cold rolling and accumulative roll-bonding, followed by annealing for recovery and structural coarsening,...

article

Solute Clusters/Enrichment at the Early Stage of Ageing in Mg–Zn–Gd Alloys Studied by Atom Probe Tomography

Xin-Fu Gu, Tadashi Furuhara, Leng Chen, Ping Yang

Acta Metallurgica Sinica (English Letters) > 2019 > 32 > 2 > 187-193

Three-dimensional distribution of solute elements in an Mg–Zn–Gd alloy during ageing process is quantitatively characterized by three-dimensional atom probe (3DAP) tomography. Based on the radius distribution function, it is found that Zn–Gd solute pairs in Mg matrix appear mainly at two peaks at early stage of ageing, and the separation distance between Zn and Gd atoms could be well rationalized...

article

Microstructure of reverted austenite in Fe-0.3N martensite

Mitsutaka Sato, Sou Matsumoto, Goro Miyamoto, Tadashi Furuhara

Scripta Materialia > 2018 > 156 > C > 85-89

Reverse transformation behavior during intercritical annealing was studied in Fe-0.3 mass%N binary alloy. Two morphologies of acicular and globular austenite are formed during reversion. The globular austenite has almost same orientation with one side of adjacent prior austenite grain and grows into the martensite with larger deviation angle from Kurdjumov-Sachs orientation relationship (K-S OR)....

article

Analysis of the interaction between moving α/γ interfaces and interphase precipitated carbides during cyclic phase transformations in a Nb-containing Fe-C-Mn alloy

Haokai Dong, Hao Chen, Wei Wang, Yongjie Zhang, more

Acta Materialia > 2018 > 158 > C > 167-179

The interaction between moving α/γ interfaces and interphase precipitated (IPd) carbides during the austenite (γ) to ferrite (α) and the ferrite (α) to austenite (γ) transformation has been systematically investigated through cyclic phase transformation experiments for a 0.1C-1.5Mn alloy containing 0.1 wt% Niobium (Nb) and its Nb-free counterpart. Shifts in the critical reaction temperatures during...

article

Three-dimensional atom probe analysis of boron segregation at austenite grain boundary in a low carbon steel - Effects of boundary misorientation and quenching temperature

Goro Miyamoto, Ai Goto, Naoki Takayama, Tadashi Furuhara

Scripta Materialia > 2018 > 154 > C > 168-171

Segregation of boron at random austenite grain boundaries with known misorientation angle in a boron-added low carbon steel quenched from austenite state at different temperatures was investigated quantitatively using three-dimensional atom probe. Boron segregation is reduced at low angle boundaries or low quenching temperatures. The latter result indicates that non-equilibrium boron segregation plays...

article

On the atomic structure of γ″ phase in Mg-Zn-Gd alloy

Xin-Fu Gu, Tadashi Furuhara, Takanori Kiguchi, Toyohiko J. Konno, more

Scripta Materialia > 2018 > 146 > C > 64-67

The atomic structure of γ″ phase in an Mg-Zn-Gd alloy has been determined by atomic resolution high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) and first-principles calculation. The γ″ phase has a hexagonal structure with three atomic layers paralleling to basal plane. It is found that the atomic positions in the middle layer are not coincide with HCP structure...

article

Orientation of austenite reverted from martensite in Fe-2Mn-1.5Si-0.3C alloy

Xianguang Zhang, Goro Miyamoto, Yuki Toji, Shoichi Nambu, more

Acta Materialia > 2018 > 144 > C > 601-612

The orientation of austenite (γ) reverted from lath martensite has been studied using electron backscatter diffraction (EBSD) in Fe-2%Mn-1.5%Si-0.3%C (mass%) alloy. Two morphologies of γ, acicular and globular, are formed during reversion. Nucleation sites for acicular γ are lath, block and sub-block boundaries, while those for globular γ are prior γ grain boundaries, as well as inside packets. Both...

article

A quantitative investigation of the effect of Mn segregation on microstructural properties of quenching and partitioning steels

Farideh HajyAkbary, Jilt Sietsma, Roumen H. Petrov, Goro Miyamoto, more

Scripta Materialia > 2017 > 137 > C > 27-30

Quenching and partitioning (Q&P) process of a 0.3C-1.3Si-3.2Mn (wt%) steel with Mn segregation is studied experimentally and theoretically. During initial quenching a higher fraction of martensite forms in Mn-poor regions compared to Mn-rich regions. In the partitioning process, austenite in Mn-poor regions is surrounded with a higher fraction of martensite than austenite in Mn-rich regions and...

article

Erratum to: Grain Refinement by Cyclic Displacive Forward/Reverse Transformation in Fe-High-Ni Alloys

Tadachika Chiba, Hassan Shirazi, Goro Miyamoto, Tadashi Furuhara

Metallurgical and Materials Transactions A > 2017 > 48 > 9 > 4423-4423

The online version of the original article can be found under doi: 10.1007/s11661-017-4152-4 .

article

Grain Refinement by Cyclic Displacive Forward/Reverse Transformation in Fe-High-Ni Alloys

Tadachika Chiba, Hassan Shirazi, Goro Miyamoto, Tadashi Furuhara

Metallurgical and Materials Transactions A > 2017 > 48 > 9 > 4204-4210

A novel method for grain refinement of martensite structures was proposed, in which transformation strain is accumulated by cyclic displacive forward and reverse transformations. This method can refine martensite structures in an Fe-18Ni alloy because a high density of austenite dislocations is introduced by a displacive reverse transformation in addition to an inheritance of dislocations in body-centered...

article

Crystallography and Interphase Boundary of Martensite and Bainite in Steels

Tadashi Furuhara, Tadachika Chiba, Takeshi Kaneshita, Huidong Wu, more

Metallurgical and Materials Transactions A > 2017 > 48 > 6 > 2739-2752

Grain refinements in lath martensite and bainite structures are crucial for strengthening and toughening of high-strength structural steels. Clearly, crystallography of transformation plays an important role in determining the “grain” sizes in these structures. In the present study, crystallography and intrinsic boundary structure of martensite and bainite are described. Furthermore, various extrinsic...

article

Analysis of the mechanical behavior of a 0.3C-1.6Si-3.5Mn(wt%) quenching and partitioning steel

Farideh HajyAkbary, Jilt Sietsma, Goro Miyamoto, Naoya Kamikawa, more

Materials Science and Engineering: A > 2016 > 677 > C > 505-514

A 0.3C-1.6Si-3.5Mn(wt%) steel was subjected to different Q&P treatments, leading to different combinations of initial martensite, bainite, secondary martensite, and retained austenite. In this study, initial martensite refers to the martensite formed during the initial quenching step and then subjected to an isothermal treatment at 400°C; secondary martensite refers to martensite formed during...

chapter

Formation of Ultrafine Grained Ferrite + Cementite Duplex Structure by Warm Deformation

Tadashi Furuhara, Behrang Poorganji

Advanced Steels > Advanced Steel Processing and Fabrication > 495-500

The microstructure change by warm deformation in low alloy steels with different initial ferrite (α) + cementite (θ) duplex structures is discussed in the present paper. In high carbon steels, heterogeneous deformation introduced in pearlite containing lamellar θ promotes dynamic recrystallization (DRX) of α for mild deformation of less than 1.2 in true strain. On the other hand, the original α grains...

article

Analysis of recrystallization behavior of hot-deformed austenite reconstructed from electron backscattering diffraction orientation maps of lath martensite

Manabu Kubota, Kohsaku Ushioda, Goro Miyamoto, Tadashi Furuhara

Scripta Materialia > 2016 > 112 > C > 92-95

The recrystallization behavior of hot-deformed austenite of a 0.55% C steel at 800°C was investigated by a method of reconstructing the parent austenite orientation map from an electron backscattering diffraction orientation map of lath martensite. Recrystallized austenite grains were clearly distinguished from un-recrystallized austenite grains. Very good correlation was confirmed between the static...

article

Interaction of carbon partitioning, carbide precipitation and bainite formation during the Q&P process in a low C steel

Farideh HajyAkbary, Jilt Sietsma, Goro Miyamoto, Tadashi Furuhara, more

Acta Materialia > 2016 > 104 > C > 72-83

Theoretical understanding of the “quenching and partitioning” (Q&P) process allowed developing microstructures consisting of carbon-depleted martensite and retained austenite that deliver superior mechanical properties. Most of the models describing the Q&P process are limited to systems in which carbide precipitation in martensite and decomposition of austenite to bainite are totally suppressed...

article

Formation of grain boundary ferrite in eutectoid and hypereutectoid pearlitic steels

Goro Miyamoto, Yosuke Karube, Tadashi Furuhara

Acta Materialia > 2016 > 103 > C > 370-381

Formation of grain boundary ferrite (GB-α) in high carbon pearlitic steels deteriorates ductility of steel wires. Since it is generally believed that fully pearlitic structure forms in eutectoid steels, GB-α formation in eutectoid or even hypereutectoid steels is curious. Therefore, effects of temperature and carbon content on the formation of GB-α in Fe-1mass%Mn-(0.75 and 1.05) mass%C alloys transformed...

article

Precipitation Modeling in Nitriding in Fe-M Binary System

Yusaku Tomio, Goro Miyamoto, Tadashi Furuhara

Metallurgical and Materials Transactions A > 2016 > 47 > 10 > 4970-4978

Precipitation of fine alloy nitrides near the specimen surface results in significant surface hardening in nitriding of alloyed steels. In this study, a simulation model of alloy nitride precipitation during nitriding is developed for Fe-M binary system based upon the Kampmann–Wagner numerical model in order to predict variations in the distribution of precipitates with depth. The model can predict...

article

Fe-Fe3C binary phase diagram in high magnetic fields

Yoshifuru Mitsui, Yuki Ikehara, Kohki Takahashi, Shojiro Kimura, more

Journal of Alloys and Compounds > 2015 > 632 > C > 251-255

The Fe-Fe₃C binary phase diagram under high magnetic fields up to 21T was investigated by a differential thermal analysis. Applying a magnetic field of 18T, the α–γ transformation temperature T_α–γ for pure iron increased quadratically from 1181K (a zero field) to 1206K. With increasing magnetic field strength, the transformation temperature A_c1 (α-Fe+cementite→α-Fe+γ-Fe) increased linearly from ∼1000K...

article

Stress–strain behavior of ferrite and bainite with nano-precipitation in low carbon steels

Naoya Kamikawa, Kensuke Sato, Goro Miyamoto, Mitsuhiro Murayama, more

Acta Materialia > 2015 > 83 > C > 383-396

We systematically investigate stress–strain behavior of ferrite and bainite with nano-sized vanadium carbides in low carbon steels; the ferrite samples were obtained through austenite/ferrite transformation accompanied with interphase precipitation and the bainite samples were via austenite/bainite transformation with subsequent aging. The stress–strain curves of both samples share several common...

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Search results for: Tadashi Furuhara

Effect of Ferrite/Martensite Phase Size on Tensile Behavior of Dual-Phase Steels with Nano-Precipitation of Vanadium Carbides

Strengthening Mechanisms in Ultrafine-Grained and Sub-grained High-Purity Aluminum

Solute Clusters/Enrichment at the Early Stage of Ageing in Mg–Zn–Gd Alloys Studied by Atom Probe Tomography

Microstructure of reverted austenite in Fe-0.3N martensite

Analysis of the interaction between moving α/γ interfaces and interphase precipitated carbides during cyclic phase transformations in a Nb-containing Fe-C-Mn alloy

Three-dimensional atom probe analysis of boron segregation at austenite grain boundary in a low carbon steel - Effects of boundary misorientation and quenching temperature

On the atomic structure of γ″ phase in Mg-Zn-Gd alloy

Orientation of austenite reverted from martensite in Fe-2Mn-1.5Si-0.3C alloy

A quantitative investigation of the effect of Mn segregation on microstructural properties of quenching and partitioning steels

Erratum to: Grain Refinement by Cyclic Displacive Forward/Reverse Transformation in Fe-High-Ni Alloys

Grain Refinement by Cyclic Displacive Forward/Reverse Transformation in Fe-High-Ni Alloys

Crystallography and Interphase Boundary of Martensite and Bainite in Steels

Analysis of the mechanical behavior of a 0.3C-1.6Si-3.5Mn(wt%) quenching and partitioning steel

Formation of Ultrafine Grained Ferrite + Cementite Duplex Structure by Warm Deformation

Analysis of recrystallization behavior of hot-deformed austenite reconstructed from electron backscattering diffraction orientation maps of lath martensite

Interaction of carbon partitioning, carbide precipitation and bainite formation during the Q&P process in a low C steel

Formation of grain boundary ferrite in eutectoid and hypereutectoid pearlitic steels

Precipitation Modeling in Nitriding in Fe-M Binary System

Fe-Fe3C binary phase diagram in high magnetic fields

Stress–strain behavior of ferrite and bainite with nano-precipitation in low carbon steels

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