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Tsuru, Tomohito; Yuge, Koretaka*; Aoyagi, Yoshiteru*; Shimokawa, Tomotsugu*; Kubo, Momoji*; Ogata, Shigenobu*
no journal, ,
High entropy alloys (HEAs) are chemically complex single- or multi-phase alloys with crystal structures. There are no major components but five or more elements are included with near equiatomic fraction. In such a situation, deformation behavior can no longer be described by conventional solid solution strengthening model. Some HEAs, indeed, show higher strengthening behavior and anomalous slip. However, the mechanisms of these features have yet to be understood. In the present study, we investigate the core structure of dislocations in BCC-HEAs using density functional theory (DFT) calculations. We found that core structure of a screw dislocation is identified as is the case with common BCC metals. On the other hand, dislocation motion should be different from pure BCC metals because of chemical and configurational disorder around dislocation core. We confirmed the specific feature of dislocation motion in HEAs by two-dimensional Peierls potential surface.
Ishikawa, Norito; Kondo, Keietsu; Fujimura, Yuki; Kitamura, Akane
no journal, ,
When ceramic materials are irradiated with swift heavy ions, radiation damages are created. In this study, Al
O
is irradiated with ions, and change in lattice spacing is analyzed for visualizing spatial mapping of the lattice change. As a result, the effect appeared near the boundary between irradiated are and unirradiated area, although the homogeneous irradiation is performed.
Abe, Yosuke; Okubo, Nariaki; Sato, Yuki*
no journal, ,
One-dimensional (1D) migration of self-interstitial atom (SIA) clusters is known to affect the radiation-induced microstructural evolution in crystalline materials. By in-situ observation using high-voltage electron microscopy in self-ion irradiated alpha-iron, we examined a role of 1D migration of SIA clusters under cascade damage condition. The results suggest that the 1D migration frequency was almost proportional to the irradiation beam intensity, indicating that the displacement by high-energy irradiation provides a trigger for causing 1D migration by detrapping the stationary SIA clusters from the bounded traps, as demonstrated under electron irradiation. On the other hand, the 1D migration distances were considerably shorter under ion irradiation than those under electron irradiation, suggesting that the candidate traps for one-dimensionally migrating SIA clusters are not only impurity/solute atoms, as revealed under electron irradiation, but also directly formed defect clusters by collision cascade under ion irradiation.
Suzudo, Tomoaki; Ebihara, Kenichi; Tsuru, Tomohito
no journal, ,
BCC metals are used in various applications as structural materials, but they are known to be brittle at low temperatures, and the brittleness is promoted by impurities such as hydrogen. Brittle fracture is a macroscopic phenomenon, while crack propagation is also a microscopic phenomenon caused by the breaking of interatomic bonds. Therefore, it is necessary to accurately reproduce the atomistic configuration and the stress concentration at the crack tip, and to predict the breaking of the interatomic bond and the plastic deformation caused thereby. In this presentation, molecular dynamics (MD) simulations of BCC Fe were performed as an example to model the crack propagation in the grains and at the grain boundaries of BCC metals. In those results, the phenomenon that crack propagation was suppressed by the emission of dislocations was microscopically reproduced.
Nakahara, Kaito*; Kawada, Rio*; Irisawa, Eriko; Ueda, Mitsutoshi*; Kawamura, Kenichi*
no journal, ,
In order to develop oxygen sensor using oxide scales formed on the surface of zirconium alloy, we focused on zirconium and copper alloy system. It was expected that the oxide scale of Zr oxide on the alloy is thin and elaborate compared with that on the pure Zr because the activity of Zr in the alloy is reduced and the oxidation rate of alloy become slow. Therefore the oxidation behavior and mechanism of two phase alloy, Zr-35Cu which is composed of ZrCu and Zr
Cu
, was studied. The results showed the oxidation rate of the alloy was same with that of the pure Zr.
Oka, Hiroshi; Tanno, Takashi; Yano, Yasuhide; Otsuka, Satoshi; Kaito, Takeji; Tachi, Yoshiaki
no journal, ,
As part of the development of mass production technology for ODS steel cladding tubes, a large attritor ball-mill PATTRIODS (Prototype large ATTRItor for mass production of ODS steel) was developed, which is a mechanical alloying device for mass production. The powder amount of throughput of PATTRIODS is 30 kg, which is three times the conventional small type attritor. In order to control the amount of oxygen during mechanical alloying, inert gas replacement capability for the pulverization tank and the powder collecting container is adopted. The production test of ODS steel using PATTRIODS revealed that PATTRIODS had the same level of oxygen controllability as the existing small type attritor.