Transformation super plasticity deformation of reduced activation ferritic/martensitic steel

Reduced Activation Ferritic/Martensitic (RAFM) steel is a promising candidate for the blanket structural materials of fusion reactors. One of the key issues in the use of RAFM for the blanket is its low workability. As a solution of this issue, innovative processing technology based on the transformation super plasticity (TSP) was proposed. In general, TSP is known as high temperature creep deformation which is induced by phase transformation. In this study, tensile tests under constant load were carried out with cyclic temperature variation for a RAFM steel to investigate the effect of cyclic temperature variations on elongation. The result of the tensile test under constant load for the RAFM steel with cyclic temperature variations exhibited a macro-elongation to 172%. The results of the tensile tests with varying loads showed the possibility of reducing the necessary time and enhancing the controllability for the formation of RAFM steel products using TSP

Effect of atmospheric control during MA-HIP process on mechanical properties of oxide dispersion-strengthened Cu alloy

In this study, mechanical properties of Dispersion Strengthened (DS)-Cu-Al (aluminum) and Zr (zirconium) alloys, which were fabricated by an MA-HIP method, were investigated for application to the heat sink materials of fusion reactors. The effect of air exposure before the HIP process was studied using a NIFS-Sealing Device. Cu–Al specimen with air exposure before HIP was broken during wire-electrical discharge formation. Cu–Al specimen without air exposure exhibited high fracture strength, but without yielding. Cu–Zr specimen, both with and without the exposure, yielded and exhibits elongation. An increase in yield and tensile strength by approximately 61% and 45%, respectively, were obtained for Cu–Zr specimen by avoiding air exposure. The results showed that Cu–Zr specimen is less susceptible to the atmosphere of the MA-HIP process than Cu–Al

Solid state diffusion bonding of doped tungsten alloys with different thermo-mechanical properties

To develop joints using W materials with different thermo-mechanical properties, solid state diffusion bonding involving two different W materials (pure W, K-doped W, or K-doped W-3%Re) and using a pure V interlayer (1.5 mm, 0.5 mm, or 0.05 mm thick) were carried out at 1250 °C for 1 h. The use of a thin interlayer was found to be effective from the point of optimizing the strength and thermal diffusivity. Diffusion bonding at lower temperatures or utilizing W materials with higher recrystallization temperatures were also determined to be effective because pure W can recrystallize at 1250 °C. Further evaluation of a wide range of interlayer thicknesses and thermo-mechanical test conditions is necessary based on the present work to obtain optimum W/V/W joints

Microstructure and mechanical properties of mechanically alloyed ODS copper alloy for fusion material application

Advanced oxide dispersion strengthened copper alloys are promising structural materials for application in divertor system of future fusion reactors due to high irradiation resistance, high thermal conductivity, and good mechanical properties. In this study, a new ODS copper including 0.42wt%Y2O3 nanosized oxide particles wasdeveloped successfully by mechanical alloying method using addition of 1 wt% Stearic acid in Ar atmosphere.Mechanical alloying resulted in decrease of crystallite size to 28 nm in concurrent with increment of dislocation density and hardness to the saturated level of × −1.7 10 m15 2 and 226HV0.1 after 48 h milling, respectively.Consolidated ODS copper by SPS and then hot roll-annealing at 900 °C/60 min showed an average grain size of 1.1 μm with a near random texture. Furthermore, TEM observations demonstrated fine semicoherent Y2O3 oxide particles distributed with a misfit parameter (δ) of 0.17 in copper matrix with an average size of 10.8 nm andinterparticle spacing of 152 nm. Finally, tensile test evaluation determined comparable mechanical properties of the annealed ODS copper (Cu-0.42wt%Y2O3) with Glidcop-Al25 including a yield strength of 272 MPa and total elongation of 12%, by two mechanisms of grain boundary strengthening and oxide particle strengthening

Microstructure development and high tensile properties of He/H2 milled oxide dispersion strengthened copper

This study describes the effect of microstructural development on high tensile properties of a newly developed He/H2 milled oxide dispersion strengthened copper in a large centimeter sized spherical morphology. Electron back scattered diffraction showed development of a strong texture of (110) plane in micron sized (1.2 μm) grains on the surface of milled spheres. A combination of microstructural features of inhomogeneous grain size, nanoscale lenticular/rectangular deformation twins, high dislocation density and fine oxide particles distribution induced a very high ultimate tensile strength (688 MPa)-ductility (8.6% elongation)

Brass-texture induced grain structure evolution in room temperature rolled ODS copper

Currently, advanced ODS copper alloy is under study as a potential fusion material providing good mechanical properties. In this work, in order to develop a high performance ODS copper containing 0.5 wt% Y2O3 oxide particles, the effect of room temperature rolling and subsequent annealing on the grain structure evolution, texture development and tensile properties are studied using EBSD, TEM and tensile tests. Microstructure evolution studies show the grain structure coarsens by enhancing the Brass texture during increase of rolling reduction and a unique single crystal-like brass-texture deformed structure is achieved after 80% rolling reduction. We found the deformation mechanism of partial slip by a/6 ⟨211⟩ by dislocations facilitated by the pinning of a/2 ⟨101⟩ perfect dislocations through fine oxide particles is responsible for formation of Brass texture during room temperature rolling. Furthermore, the recrystallization of ODS copper retards to high temperature of ~700 °C and shows a fine-grained microstructure with different orientations of Goss, Brass, S and Copper. Evaluation of microstructure-mechanical properties of the recrystallized samples expresses that the bimodal grain size distribution at 800 °C for 30 min offers a good tensile strength-ductility (UTS: 491 MPa, elt: 19%) at ambient temperature

Nd3+-activated CaF2 ceramic lasers

Nd,Y:CaF2 and Nd,La:CaF2 ceramics featuring good optical quality have been fabricated by reactive sintering and a hot isostatic pressing method. The transmission spectra, emission spectra, and fluorescence decay curves were measured. Lasing at 1064 and 1065 nm was observed in Nd,Y:CaF2 and Nd,La:CaF2, respectively, upon quasi-continuous-wave pumping by a diode laser emitting at 791 nm. To the best of our knowledge, this is the first demonstration of Nd3+-activated CaF2 ceramic laser

Microstructure development in cryogenically rolled oxide dispersion strengthened copper

Recently, advanced oxide dispersion strengthened (ODS) copper alloys have been developed using mechanical alloying process as a fusion material. In this study, to develop a superior ODS copper alloy containing 0.5wt% Y2O3, the effect of cryogenic rolling on microstructure development and tensile properties was studied using high resolution EBSD, TEM and tensile tests. During cryogenic deformation of ODS copper, grain structure remains in submicron size scale as a combinatorial result of geometrically effects, nanotwin bundle deformation, interaction of dislocations with fine oxide particles and some diffusional processes including static recovery and recrystallization. Clear microstructural characterizations confirmed nucleation of fine new oriented recrystallized grains mainly on the HABs of 80%cryogenic rolled ODS copper. Quantitative analyses indicated grain boundary migration at room temperature following cryogenic deformation originated from high driving force induced by grain boundary bulging and high mobility induced by vacancies. The tensile properties of cryogenic deformed samples showed superior tensile strength than room temperature deformation leading to UTS: 624 MPa, elt: 5.5%, while saturation of strength between 60%-80% reduction, approved occurrence of softening by diffusional processes

PETREL for Astrophysics and Carbon Business

A multi-purpose 50kg class microsatellite hosting astrophysical mission and earth remote sensing, PETREL , will be launched in 2023. In the night side, PETREL observe the ultra-violet sky with a wide-field telescope covering 50 deg^2 for surveying transient objects related to supernovae, tidal disruption events, and gravitational wave events. Our UV telescope can detect the early phase UV emission from a neutron star merger occurred within 150 Mpc. In addition to the satellite observation, PETREL sends a detection alert including the coordinate and brightness of the UV transient to the ground via the real time communication network within several minutes after detection to conduct follow-up observations with the collaborating ground based observatories over the world. In the day side, PETREL observes the surface of the earth by using the tunable multi-spectral cameras and a ultra-compact hyperspectral camera. Our potential targets are the tropical forests (Green Carbon) and coastal zones (Blue Carbon) in the tropical areas to evaluating the global biological carbon strages. For this purpose PETREL will conduct multiple scale mapping collaborating with drones and small aircraft not only satellite. The obtained data will be used for academical research and for business applications. The technical difficulty of this satellite is that carries out multi-purpose with different requirements, such as astronomical observations which requires a quite high attitude stability and the earth observations requiring a high pointing accuracy, with limited resources. If it is possible, a novel small satellite system or a business style can be realized that can share the payload with academia and industry. PETREL has been adopted as Innovative Satellite Technology Demonstration Program No.3 led by JAXA, and development is underway with the aim of launching in FY2023

Improvement of thermal conductivity by adding tungsten and/or copper wire in F82H

The F82H, which is one of reduced activation ferritic/martensitic steels, is a strong candidate structure material for fusion reactor because of its satisfactory mechanical property and high swelling resistance in the operating temperature range. One disadvantage of F82H would be its low thermal conductivity as a structural material for divertor. In this study, we have fabricated several F82H-based composite materials by the spark plasma sintering to improve its thermal conductivity by adding tungsten and/or copper wires. F82H-20 vol.% W and F82H-10 vol.% W-10 vol.% Cu composites included reaction layers at the interface between tungsten wire and F82H matrix, resulting in the decrease in ductility and tensile strength because of the formation of tungsten carbide. On the other hand, F82H-20 vol.% Cu composite, sintered for 120 min at 1000°C, included no reaction layers and showed the highest thermal conductivity with a high relative density. Furthermore, it showed a great tensile property, which is comparable to that of the original F82H