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Caused corrosion by hydrogen on stainless steel using nondestructive technique is one of issues to be clarified in nuclear fusion industry. In this study, an ultrasonic wave was used to evaluate the degree of corrosion by hydrogen charging of stainless steel. The mechanical properties of hydrogen charged material including tensile strength and strain were discussed, and the change of surface of specimen according to the hydrogen charging quantities was observed. The relationship between fractography and ultrasonic wave characteristics on hydrogen charged material discussed. In addition, acoustic emission technique was applied to clarify the dynamic behavior such as dislocation, deformation and crack in material by loading. AE parameters of event, energy, amplitude and frequency were analyzed according to the degree of load, and optical AE parameter was derived to evaluate the degree of the damage of hydrogen charged stainless steel.

The objective of this study is to evaluate the elastic wave's characteristic on the crack in the weld of stainless steel materials using guided wave and acoustic emission, nondestructive tests. The stainless steel is expected as candidate of structural piping material under high temperature condition in nuclear fusion instrument, and a tungsten inert gas (TIG) weld technique was applied for making its jointing. The defect size of 20 mm was induced in the weld material. The guided wave, one of elastic waves, can propagate through very long pipe, and easily change to lots of modes by the defects in the structure. By analyzing the relationship between the mode conversion and the defects we can evaluate existing of the defects in weld material. In present study Nd-YAG laser was used to excite the guided wave by non-contact method, and AE technique was also used to clarify the mode conversion of guided wave by defect because lots of AE parameters of energy, count and amplitude can give more chances for analysis of mode conversion. The optimal AE parameters for the evaluation of the defects in weld zone using laser guided wave were derived.

The effects of hydro co-extrusion on the microstructure changes of aluminum hybrid duo-cast Al 3003/Al 4004 clad materials were studied. The specimen of duo-cast Al 3003/Al 4004 clad materials was in circle shape, and was composed of Al 3003(outside) and Al 4004(inside) materials. The specimen was extruded by the hydro co-extrusion equipment. The manufacturing conditions of the specimen were 423 K in temperature and 5 in extrusion ratio. The dimensions of the specimen were 80 mm in diameter of the Al 4004 material and 35 mm in thickness of the Al 3003 material before the hydro co-extrusion process, and 30 mm in diameter and about 5 mm in thickness after the extrusion process, respectively. The microstructure and the hardness for two specimens were investigated. The hardness value of cross section in the duo-cast Al 3003/Al 4004 clad materials before the extrusion process was increased in form of the parabola toward the center. However, after the extrusion process, it was almost constant in the portion of Al 4004 material. Lots of big voids above 1 mm in diameter in the specimen existed in the interfacing region of Al 3003 and Al 4004 materials before the extrusion process. These big voids disappeared after the process of hydro co-extrusion.

Cu/Al bar clad material was fabricated by a drawing process and a subsequent heat treatment. During these processes, intermetallic compounds have been formed at the interface of Cu/Al and have affected its bonding property. Microstructures of Cu/Al interfaces were observed by OM, SEM and EDX Analyser in order to investigate the bonding properties of the material. According to the microstructure a series of diffusion layers were observed at the interface and the thicknesses of diffusion layers have increased with aging time as a result of the diffusion bonding. The interfaces were composed of 3-ply diffusion layers and their compositions were changed with aging time at 400 °C. These compositional compounds were revealed to be η2, (θ+η2), (α+θ) intermetallic phases. It is evident from V-notch impact tests that the growth of the brittle diffusion layers with the increasing aging time directly influenced delamination distance between the Cu sleeve and the Al core. It is suggested that the proper holding time at 400 °C for aging as post heat treatment of a drawn Cu/Al bar clad material would be within 1 h.

This paper dealt with a liquid phase sintering process for the fabrication of carbon fiber reinforced SiC matrix composites (Cf/SiC), using a ultra-fine SiC particles and oxide additive materials. Especially, the thermal shock properties of Cf/SiC composites were investigated at the elevated temperatures. The characterization of monolithic SiC materials by the variation of starting SiC particle size was also examined. Monolithic SiC materials possessed an excellent density higher than about 3.0 mg/m3 and a good flexural strength of about 700 MPa, regardless of starting SiC particle size. Cf/SiC composites also represented a dense morphology in the intra-fiber bundle region, even if there were some amount of pores. However, the flexural strength of Cf/SiC composites greatly decreased at the thermal shock temperature of 400 °C.

The effect of He-injection on irradiation-induced segregation of aging treated Fe–12%Cr–15%Mn austenitic steels, which are candidate materials as the reduced radio-activation of structure material for nuclear and/or fusion reactors was investigated by using the 1250 kV high voltage electron microscope (HVEM) connected with an ion accelerator. The Fe–Mn–Cr steel has been irradiated at 573 K by three irradiation modes of single electron-beam irradiation, electron-beam irradiation after He-injection and electron/He+-ion dual-beam irradiation in a HVEM. Irradiation-induced segregation analyses were carried out by an energy dispersive X-ray analyzer (EDX) in a 200 kV FE-TEM with beam diameter of about 0.5 nm. Dislocation loops with strain contrast were formed during irradiation and the loop numbers density increased rapidly with irradiation dose for He-pre-injected specimens. Voids were not observed after irradiations with three irradiation modes up to 5.4 dpa at 573 K. Irradiation-induced segregations of Cr and Mn near grain boundary were observed in each irradiation condition, but the amounts of Mn segregation decreased in the cases of electron/He+-ion dual-beam irradiation compared with single electron-beam and electron-beam irradiation after He-injection conditions.

This paper dealt with the thermal shock properties of SiCf/SiC composites reinforced with two dimensional SiC fabrics. SiCf/SiC composites were fabricated by a liquid phase sintering process, using a commercial nano-size SiC powder and oxide additive materials. An Al2O3–Y2O3–SiO2 powder mixture was used as a sintering additive for the consolidation of SiC matrix region. In this composite system, Tyranno SA SiC fabrics were also utilized as a reinforcing material. The thermal shock test for SiCf/SiC composites was carried out at the elevated temperature. Both mechanical strength and microstructure of SiCf/SiC composites were investigated by means of optical microscopy, SEM and three point bending test. SiCf/SiC composites represented a dense morphology with a porosity of about 8.2% and a flexural strength of about 160 MPs. The characterization of SiCf/SiC composites was greatly affected by the history of cyclic thermal shock. Especially, SiCf/SiC composites represented a reduction of flexural strength at the thermal shock temperature difference higher than 800 °C.

The abrasive wear patterns and the tensile properties of steel saw wires (120 μm in diameter) were investigated in order to develop highly reliable saw wires for the application to silicon (Si) ingot slicing. Saw wires that underwent heat treatment at different linear velocities during the patenting process were subjected to 2-body abrasive wear (2-BAW) and 3-body abrasive wear (3-BAW) tests. The 2-BAW and 3-BAW tests of the saw wires showed opposite trends in abrasive wear resistance. The wear loss resulting from the 2-BAW test was mainly determined by the tensile strength and microhardness of the steel saw wire samples, while the wear loss from the 3-BAW test was primarily determined by the elongation, or ductility, of the samples.

This paper dealt with the microstructure and mechanical properties of SiC based composites reinforced with different reinforcing materials. The composites were fabricated using reinforcing materials of carbon nanotubes (CNT) and Tyranno Lox-M SiC chopped fibers. The volume fraction of carbon nanotubes was also varied in this composite system. An Al2O3–Y2O3 powder mixture was used as a sintering additive in the consolidation of the SiC matrix. The characterization of the composites was investigated by means of SEM and three point bending tests. These composites showed a dense morphology of the matrix region, by the creation of a secondary phase. The composites reinforced with SiC chopped fibers possessed a flexural strength of about 400 MPa at room temperature. The flexural strength of the carbon nanotubes composites had a tendency to decrease with increased volume fraction of the reinforcing material.

To investigate the effect of aging treatment on irradiation-induced segregation of high Mn-Cr steel, specimens for electron-beam irradiation were prepared from the high Mn-Cr austenitic steel which was solution treated at 1 373 K for 1 h and aging treated at 573 K for 1 000 h, respectively. The electron-beam irradiation was performed at 573 K up to doses of 5.4 dpa in a 1 250 kV HVEM and irradiation-induced segregation analyses were carried out by an EDX in a 200 kV FE-TEM. The results show that void formation is not observed in both solution treated and aging treated ones. The amount of Cr segregation at the grain boundary decreases in the aged one; however, that of Mn is not changed in solution treated one.

The matrix and heat affected zone (HAZ) of welded SUS304 steel has been irradiated in an 1250 kV high voltage electron microscope at 673 K to 5.4 dpa (displacements per atom) to study the effect of electron irradiation on microstructure. In situ observation shows the voids formed by electron-beam irradiation coalescence which grew to larger sizes with irradiation dose. Values of void size, void number density and void swelling in HAZ were larger than those of the matrix, and these increased and saturated gradually with irradiation dose. Non-equilibrium segregation phenomenon involving Cr depletion and Ni enrichment at grain boundaries were also observed in both the HAZ and matrix of welded SUS304 steel.

This paper concerns the liquid phase sintering (LPS) process for the fabrication of SiC based ceramic materials and their characterization. The submicron SiC powder was also utilized for the improvement of LPS-SiC materials. A thermal exposure test was carried out to examine the high temperature stability of LPS-SiC materials. A mixture of Al 2 O 3 and Y 2 O 3 particles was used as an additive in the LPS process. LPS-SiC materials were fabricated by various sintering parameters such as sintering temperature, additive composition ratio (Al 2 O 3 /Y 2 O 3 ) and additive amount (Al 2 O 3 + Y 2 O 3 ). The strength of LPS-SiC materials was examined at room temperature using a three-point bending test. LPS-SiC materials fabricated at 1820 °C had a density of about 3.1 g/cm 3 and a flexural strength of about 780 MPa. However, the strength of LPS-SiC materials substantially decreased after the thermal exposure at 1400 °C for 10 h in the Ar atmosphere, due to the dramatic increase of weight loss by severe erosion.

The interaction between dislocations and nitride precipitates during high-temperature creep deformation of high manganese austenitic steels has been investigated by transmission electron microscopy. Most of the dislocations activated by applied stress were dissociated into Shockley partials. The fine TiN precipitates are pinning and/or incorporating the bow-type moving dislocations and they turned out to be more effective than the coarser TaN in disturbing the dislocation movement.

The heat affected zone (HAZ) of a welded SUS304 steel has been irradiated in an 1250 kV high voltage electron microscope at 673 K and up to 5.4 dpa (displacements per atom) to study the effect of electron irradiation on microstructure. The dislocation loop density of initial irradiation state increased with electron irradiation dose. Void size, void number density and void swelling increased and then saturated gradually with irradiation dose. The depletion of Cr and the enrichment of Ni at the grain boundary were also recognized by EDS analysis in the HAZ of welded SUS304 steel.

Many investigations on internal stress of various materials have been performed as the internal stress is considered to be an important factor to control high temperature deformation. The present authors have researched the effect of very fine and dense vanadium nitride (VN) precipitates on internal stress and effective stress which were measured by a strain dip test during high temperature creep of 12%Cr-15%Mn austenitic steels. In the present study, the authors have investigated the difference of the response to a strain dip test among the 12%Cr-15%Mn materials which are alloyed with small amounts of V, Ti and Ta and have different distributions of nitrides formed by an aging treatment, and have discussed the effect of nitride distribution on the interaction of dislocations with the precipitates.

High Mn-Cr austenitic steels are still considered to be an important high temperature structural material from the point of view of fast-induced radioactivity decay (FIRD) and non-magneticity. The objective of the present study is to investigate the mechanical properties of 12% Cr-15% Mn austenitic stainless steels and to compare these properties with those of the reference materials of JPCAs and JFMS, which are being investigated for the development of fusion reactor structural materials in Japan. The effects of the alloying elements V, Ti, Ta, etc. were investigated to determine the improvement of mechanical properties. Tiny precipitates of VN and Ti(C, N) raised the high-temperature strength considerably. Content of 0.1 to 0.2% C, however, formed very coarse precipitates of M 23 C 6 type carbide on the grain boundaries, which deteriorated low temperature toughness inducing intergranular fracture. Microstructural evolution during long-term aging was also investigated.