K. Hatsuda

Bio: K. Hatsuda is an academic researcher from Osaka University. The author has contributed to research in topics: Ultimate tensile strength & Equal channel angular extrusion. The author has an hindex of 1, co-authored 2 publications receiving 62 citations.

Continuous grain refinement of aluminum strip by conshearing

Abstract: The ‘conshearing’ process, a continuous version of Equal Channel Angular Extrusion was applied to 2 mm thick 1100 aluminum alloy strips at room temperature. It was found that the optimum flection angle of the ECA die (or the supplementary angle of the channel angle) to impose high strain is 65°. The 〈1 1 1〉//ND shear texture was developed and showed maximum intensity after two passes. After six passes, banded microstructure with ultrafine grains of which mean thickness and length were 0.42 and 1.4 μm, respectively, was observed. The obtained material showed well-balanced mechanical properties; i.e., a tensile strength of 170 MPa and an elongation to failure of 23%.

Improvement of the critical current density of Ag-sheathed (Bi,Pb)2223 superconducting tapes by tension rolling

Abstract: Monocore Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox tapes were prepared by the oxide-powder-in-tube method. The effects of tension during intermediate rolling between sinterings have been investigated. It has been revealed that the critical current density Jc is higher when the front and back tensions are applied simultaneously than when only one of them is applied. The excessive tension deteriorates the Jc. The optimum level of tension has been found to be ∼5 MPa. The application of tension suppresses the sausaging of silver/oxide core interface, improves the grain alignment of oxide core and results in higher Jc.

Principles of equal-channel angular pressing as a processing tool for grain refinement

Abstract: During the last decade, equal-channel angular pressing (ECAP) has emerged as a widely-known procedure for the fabrication of ultrafine-grained metals and alloys. This review examines recent developments related to the use of ECAP for grain refinement including modifying conventional ECAP to increase the process efficiency and techniques for up-scaling the procedure and for the processing of hard-to-deform materials. Special attention is given to the basic principles of ECAP processing including the strain imposed in ECAP, the slip systems and shearing patterns associated with ECAP and the major experimental factors that influence ECAP including the die geometry and pressing regimes. It is demonstrated that all of these fundamental and experimental parameters play an essential role in microstructural refinement during the pressing operation. Attention is directed to the significant features of the microstructures produced by ECAP in single crystals, polycrystalline materials with both a single phase and multi-phases, and metal–matrix composites. It is shown that the formation of ultrafine grains in metals and alloys underlies a very significant enhancement in their mechanical and functional properties. Nevertheless, it is demonstrated also that, in order to achieve advanced properties after processing by ECAP, it is necessary to control a wide range of microstructural parameters including the grain boundary misorientations, the crystallographic texture and the distributions of any second phases. Significant progress has been made in the development of ECAP in recent years, thereby suggesting there are excellent prospects for the future successful incorporation of the ECAP process into commercial manufacturing operations.

Severe Plastic Deformation (SPD) Processes for Metals

Abstract: Processes of severe plastic deformation (SPD) are defined as metal forming processes in which a very large plastic strain is imposed on a bulk process in order to make an ultra-fine grained metal The objective of the SPD processes for creating ultra-fine grained metal is to produce lightweight parts by using high strength metal for the safety and reliability of micro-parts and for environmental harmony In this keynote paper, the fabrication process of equal channel angular pressing (ECAP), accumulative roll-bonding (ARB), high pressure torsion (HPT), and others are introduced, and the properties of metals processed by the SPD processes are shown Moreover, the combined processes developed recently are also explained Finally, the applications of the ultra-fine grained (UFG) metals are discussed

Texture evolution in equal-channel angular extrusion

Abstract: The focus of this article is texture development in metals of fcc, bcc, and hcp crystal structure processed by a severe plastic deformation (SPD) technique called equal-channel angular extrusion (ECAE) or equal-channel angular pressing (ECAP). The ECAE process involves very large plastic strains and is well known for its ability to refine the grain size of a polycrystalline metal to submicron or even nano-size lengthscales depending on the material. During this process, the texture also changes substantially. While the strength, microstructure and formability of ECAE-deformed metals have received much attention, texture evolution and its connection with these properties have not. In this article, we cover a multitude of factors that can influence texture evolution, such as applied strain path, die geometry, processing conditions, deformation inhomogeneities, accumulated strain, crystal structure, material plastic behavior, initial texture, dynamic recrystallization, substructure, and deformation twinning. We evaluate current constitutive models for texture evolution based on the physics they include and their agreement with measurements. Last, we discuss the influence of texture on post-processed mechanical response, plastic anisotropy, and grain refinement, properties which have made ECAE, as well as other SPD processes, attractive. It is our intent to make SPD researchers aware of the importance of texture development in SPD and provide the background, guidance, and methodologies necessary for incorporating texture analyses in their studies.

Nanomaterials by severe plastic deformation: review of historical developments and recent advances

Abstract: Severe plastic deformation (SPD) is effective in producing bulk ultrafine-grained and nanostructured materials with large densities of lattice defects. This field, also known as NanoSPD, experienced a significant progress within the past two decades. Beside classic SPD methods such as high-pressure torsion, equal-channel angular pressing, accumulative roll-bonding, twist extrusion, and multi-directional forging, various continuous techniques were introduced to produce upscaled samples. Moreover, numerous alloys, glasses, semiconductors, ceramics, polymers, and their composites were processed. The SPD methods were used to synthesize new materials or to stabilize metastable phases with advanced mechanical and functional properties. High strength combined with high ductility, low/room-temperature superplasticity, creep resistance, hydrogen storage, photocatalytic hydrogen production, photocatalytic CO2 conversion, superconductivity, thermoelectric performance, radiation resistance, corrosion resistance, and biocompatibility are some highlighted properties of SPD-processed materials. This article reviews recent advances in the NanoSPD field and provides a brief history regarding its progress from the ancient times to modernity. Abbreviations: ARB: Accumulative Roll-Bonding; BCC: Body-Centered Cubic; DAC: Diamond Anvil Cell; EBSD: Electron Backscatter Diffraction; ECAP: Equal-Channel Angular Pressing (Extrusion); FCC: Face-Centered Cubic; FEM: Finite Element Method; FSP: Friction Stir Processing; HCP: Hexagonal Close-Packed; HPT: High-Pressure Torsion; HPTT: High-Pressure Tube Twisting; MDF: Multi-Directional (-Axial) Forging; NanoSPD: Nanomaterials by Severe Plastic Deformation; SDAC: Shear (Rotational) Diamond Anvil Cell; SEM: Scanning Electron Microscopy; SMAT: Surface Mechanical Attrition Treatment; SPD: Severe Plastic Deformation; TE: Twist Extrusion; TEM: Transmission Electron Microscopy; UFG: Ultrafine Grained GRAPHICAL ABSTRACT IMPACT STATEMENT This article comprehensively reviews recent advances on development of ultrafine-grained and nanostructured materials by severe plastic deformation and provides a brief history regarding the progress of this field.

Principles of ECAP–Conform as a continuous process for achieving grain refinement: Application to an aluminum alloy

Abstract: Equal-channel angular pressing (ECAP) combined with the Conform process provides a solution for the continuous production of ultrafine-grained materials. Rods of a commercial Al-6061 alloy were processed by ECAP–Conform at room temperature for up to a total of four passes. Microstructural observations showed significant grain refinement but with elongated grains after four passes with average widths of ∼150 nm and lengths of ∼1.2 μm when viewed on the longitudinal planes. Microhardness measurements after a single pass revealed inhomogeneities both on the cross-sectional planes and along the rod. After processing through four passes there was reasonable homogeneity throughout the rod. Measurements of the shear strengths in two orthogonal directions perpendicular to the extrusion axis showed significant strengthening after ECAP–Conform and there was no evidence for any plastic anisotropy after processing through four passes.