There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Friction stir welding (FSW) is a relatively new solid-state joining process. This joining technique is energy efficient, environment friendly, and versatile. In particular, it can be used to join high-strength aerospace aluminum alloys and other metallic alloys that are hard to weld by conventional fusion welding. FSW is considered to be the most significant development in metal joining in a decade. Recently, friction stir processing (FSP) was developed for microstructural modification of metallic materials. In this review article, the current state of understanding and development of the FSW and FSP are addressed. Particular emphasis has been given to: (a) mechanisms responsible for the formation of welds and microstructural refinement, and (b) effects of FSW/FSP parameters on resultant microstructure and final mechanical properties. While the bulk of the information is related to aluminum alloys, important results are now available for other metals and alloys. At this stage, the technology diffusion has significantly outpaced the fundamental understanding of microstructural evolution and microstructure–property relationships.

/pdf/friction-stir-welding-and-processing-3hu3ejo7ub.pdf

Friction Stir Welding and Processing

Metals have been mankind's most essential materials for thousands of years; however, their use is affected by ecological and economical concerns Alloys with higher strength and ductility could alleviate some of these concerns by reducing weight and improving energy efficiency However, most metallurgical mechanisms for increasing strength lead to ductility loss, an effect referred to as the strength-ductility trade-off Here we present a metastability-engineering strategy in which we design nanostructured, bulk high-entropy alloys with multiple compositionally equivalent high-entropy phases High-entropy alloys were originally proposed to benefit from phase stabilization through entropy maximization Yet here, motivated by recent work that relaxes the strict restrictions on high-entropy alloy compositions by demonstrating the weakness of this connection, the concept is overturned We decrease phase stability to achieve two key benefits: interface hardening due to a dual-phase microstructure (resulting from reduced thermal stability of the high-temperature phase); and transformation-induced hardening (resulting from the reduced mechanical stability of the room-temperature phase) This combines the best of two worlds: extensive hardening due to the decreased phase stability known from advanced steels and massive solid-solution strengthening of high-entropy alloys In our transformation-induced plasticity-assisted, dual-phase high-entropy alloy (TRIP-DP-HEA), these two contributions lead respectively to enhanced trans-grain and inter-grain slip resistance, and hence, increased strength Moreover, the increased strain hardening capacity that is enabled by dislocation hardening of the stable phase and transformation-induced hardening of the metastable phase produces increased ductility This combined increase in strength and ductility distinguishes the TRIP-DP-HEA alloy from other recently developed structural materials This metastability-engineering strategy should thus usefully guide design in the near-infinite compositional space of high-entropy alloys

Metastable high-entropy dual-phase alloys overcome the strength–ductility trade-off

Dynamic and post-dynamic recrystallization under hot, cold and severe plastic deformation conditions

The cold rolling behavior of a solidified columnar-crystal specimen with the 001〈 uv 0〉 initial texture in an Fe-36%Ni austenitic (f.c.c.) alloy has been investigated. The rolled microstructure and the crystal rotation strongly depended on the initial orientation of columnar grains. 70% rolled microstructure of the initially (001)[100] oriented grains was composed of three kinds of deformed microstructures: the smoothly-etched matrix with the (001)[100] orientation, the wide deformation bands roughly parallel to the transverse direction (TD) with the (101)[101¯] orientation and the narrow deformation bands parallel to the rolling direction (RD). The shear bands inclined by 30 deg from the rolling plane formed within the initially (001)[110] oriented grains, where the matrix regions rotated to the 113〈332〉 orientation. Each shear band was composed of many elongated cells whose width was less than 0.2 μ m. The formation of each deformed microstructure was discussed in connection with the active slip systems.

Effect of initial orientation on the cold-rolling behavior of solidified columnar crystals in an Fe-36%Ni austenitic alloy

/pdf/ebsd-and-ecci-based-assessments-of-inhomogeneous-plastic-2lzdt167zz.pdf

EBSD- and ECCI-based Assessments of Inhomogeneous Plastic Strain Evolution Coupled with Digital Image Correlation

Grain refining experiments for casting of pure Al were conducted to evaluate the grain refinement performance of an Al-5mass%Ti alloy refiner before and after cold rolling. Al3Ti particles in the Al-Ti alloy refiner were efficiently fragmented by cold rolling. The size of the Al3Ti particles in cold rolled Al-Ti alloy refiner decreased from 280μm to 30μm with increasing reduction ratio of cold rolling. Mean size of α-Al grains in pure Al cast refined by the cold rolled Al-Ti alloy refiner decreased from about 500μm to 200μm with increasing the reduction ratio. In order to investigate mechanical property of the pure Al cast refined by the cold rolled Al-Ti alloy refiner, Vickers hardness test and tensile test were conducted. Strength of the pure Al cast refined by the cold rolled Al-Ti alloy refiner increased with increasing the reduction ratio. The strength improvement of pure Al cast refined by the cold rolled Al-Ti alloy refiner followed Hall-Petch relationship. From obtained results, it was concluded that cold rolling for refiner is useful practical application for pure Al cast.

Grain Refinement Performance of Aluminium Cast-Alloy by Deformed Al-Al3Ti Alloy Refiner

Elastoplastic phenomena, such as plastic deformation and failure, are multi-scale, deformation-path-dependent, and mechanical-field-sensitive problems associated with metals. Accordingly, visualization of the microstructural deformation path under a specific mechanical field is challenging for the elucidation of elastoplastic phenomena mechanisms. To overcome this problem, a dislocation-resolved in-situ technique for deformation under mechanically controllable conditions is required. Thus, we attempted to apply electron channeling contrast imaging (ECCI) under tensile loading, which enabled the detection of lattice defect motions and the evolution of elastic strain fields in bulk specimens. Here, we presented the suitability of ECCI as an in-situ technique with dislocation-detectable spatial resolution. In particular, the following ECCI-visualized plasticity-related phenomena were observed: (1) pre-deformation-induced residual stress and its disappearance via subsequent reloading, (2) heterogeneous dislocation motion during plastic relaxation, and (3) planar surface relief formation via loading to a higher stress.

/pdf/in-situ-electron-channeling-contrast-imaging-under-tensile-32x9c1d8jk.pdf

In-Situ Electron Channeling Contrast Imaging under Tensile Loading: Residual Stress, Dislocation Motion, and Slip Line Formation.

Crevice corrosion was investigated in pure iron exposed to a strong acetate buffer solution. The specimens experienced the potential drop inside the crevice, which resulted in the formation of passive, active, and hydrogen evolution regions. The distribution of hydrogen evolution occurring inside the crevice was mapped using a silver decoration technique applied on the other side of the specimen. The results suggest that the entry of absorbed hydrogen show a variation in the intensity across the crevice. The crevice mouth and bottom portions showed the least hydrogen entry, whereas the intermediate portion yielded the significant amount which resulted in the accumulation of silver deposits. © 2005 The Electrochemical Society. DOI: 10.1149/1.1979367 All rights reserved.

https://www.electrochem.org/dl/support/assets/esl_v8n9_b30.pdf

Kaneaki Tsuzaki

Papers

Effect of initial orientation on the cold-rolling behavior of solidified columnar crystals in an Fe-36%Ni austenitic alloy

EBSD- and ECCI-based Assessments of Inhomogeneous Plastic Strain Evolution Coupled with Digital Image Correlation

Grain Refinement Performance of Aluminium Cast-Alloy by Deformed Al-Al3Ti Alloy Refiner

In-Situ Electron Channeling Contrast Imaging under Tensile Loading: Residual Stress, Dislocation Motion, and Slip Line Formation.

Hydrogen mapping across crevices