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Hiromichi T. Fujii

Bio: Hiromichi T. Fujii is an academic researcher from Tohoku University. The author has contributed to research in topics: Welding & Grain boundary. The author has an hindex of 16, co-authored 31 publications receiving 716 citations. Previous affiliations of Hiromichi T. Fujii include Kumamoto University & Ohio State University.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the microstructures of Al alloy 6061 subjected to very high-power ultrasonic additive manufacturing were systematically examined to understand the underlying ultrasonic welding mechanism, and it was found that the weld interface between the metal tapes consisted of fine, equiaxed grains resulting from recrystallization, which was driven by simple shear deformation along the ultrasonically vibrating direction of the tape surface.

100 citations

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TL;DR: In this paper, thermal transients from the interface regions were recorded during processing of aluminum alloy (3003 and 6061 series) and 11,000 copper tapes under similar conditions, and the observed peak temperatures were seen to increase with increase in shear strength of the material and ultrasonic vibration amplitude.

88 citations

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TL;DR: The welds with weld energies of more than 1.05 kJ fracture in the base metal and were severely deformed by the ultrasonic vibration, and recrystallization occurred around the weld interface owing to the shear deformation and heating during ultrasonic welding as discussed by the authors.

87 citations

Journal ArticleDOI
TL;DR: In this paper, the electron backscattered diffraction technique was used to characterize the interface microstructure of 3003 aluminum alloy builds with constituent tapes using a very high power ultrasonic additive manufacturing (UAM) process.
Abstract: Ultrasonically consolidated 3003 aluminum alloy builds were prepared with constituent tapes by using a very high power ultrasonic additive manufacturing (UAM) process. Microstructures of interface and bulk regions were quantitatively characterized using the electron backscattered diffraction technique. The interface microstructure consists of equiaxed grains. The 〈111〉 crystallographic directions of these grains were aligned with the normal direction of the specimen, confirming a shear deformation mode at these regions. In addition, due to recrystallization, the density of low-angle grain boundaries also significantly decreased. In contrast, original elongated grains and partially recrystallized grains were observed in the bulk region of the tape. These elongated grains correspond to rolling texture components of face-centered-cubic materials. The preceding microstructure gradients are rationalized based on the accumulated thermomechanical cycles during processing.

83 citations

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TL;DR: In this article, an anodized Al alloy 1050 was also welded to Cu and a recrystallized microstructure with shear texture was formed in the Al matrix.

70 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, a review of additive manufacturing (AM) techniques for producing metal parts are explored, with a focus on the science of metal AM: processing defects, heat transfer, solidification, solid-state precipitation, mechanical properties and post-processing metallurgy.
Abstract: Additive manufacturing (AM), widely known as 3D printing, is a method of manufacturing that forms parts from powder, wire or sheets in a process that proceeds layer by layer. Many techniques (using many different names) have been developed to accomplish this via melting or solid-state joining. In this review, these techniques for producing metal parts are explored, with a focus on the science of metal AM: processing defects, heat transfer, solidification, solid-state precipitation, mechanical properties and post-processing metallurgy. The various metal AM techniques are compared, with analysis of the strengths and limitations of each. Only a few alloys have been developed for commercial production, but recent efforts are presented as a path for the ongoing development of new materials for AM processes.

1,713 citations

Journal ArticleDOI
06 Apr 2016
TL;DR: Marshall has unique expertise in leveraging new digital tools, 3D printing, and other advanced manufacturing technologies and applying them to propulsion systems design and other aerospace materials to meet NASA mission and industry needs.
Abstract: Propulsion system development requires new, more affordable manufacturing techniques and technologies in a constrained budget environment, while future in-space applications will require in-space manufacturing and assembly of parts and systems. Marshall is advancing cuttingedge commercial capabilities in additive and digital manufacturing and applying them to aerospace challenges. The Center is developing the standards by which new manufacturing processes and parts will be tested and qualified. Rapidly evolving digital tools, such as additive manufacturing, are the leading edge of a revolution in the design and manufacture of space systems that enables rapid prototyping and reduces production times. Marshall has unique expertise in leveraging new digital tools, 3D printing, and other advanced manufacturing technologies and applying them to propulsion systems design and other aerospace materials to meet NASA mission and industry needs. Marshall is helping establish the standards and qualifications “from art to part” for the use of these advanced techniques and the parts produced using them in aerospace or elsewhere in the U.S. industrial base.

481 citations

Journal ArticleDOI
TL;DR: In this article, a comprehensive understanding of the fundamentals of the microstructural evolution during FSW/P has been developed, including the mechanisms underlying the development of grain structures and textures, phases, phase transformations and precipitation.

390 citations

Journal ArticleDOI
TL;DR: In this article, a review article summarizes the recent progresses on the complex interaction between second-phase particles and recrystallization and the science behind them, and concludes that the double-edge effect of second phase particles on the behavior and mechanical properties of metallic materials is still far from being clear.

361 citations