Microstructure and defect analysis in the vicinity of blisters in polycrystalline tungsten

AbstractUp to now, analyzing the production of dislocation-type defects in the subsurface region of plasma or ion-exposed tungsten samples has been hampered by the challenging production of suitable cross-section samples for transmission electron microscopy. We present two reliable methods based on precision electropolishing to prepare cross-sections of tungsten that allow direct imaging of dislocation-type defects by scanning as well as by transmission electron microscopy. Using these methods, we are able to demonstrate a clear enhancement of the dislocation density in the caps of blisters on tungsten exposed to H isotope plasma, i.e., of surface morphologies that are correlated to subsurface cavities. As a benchmark, we also show a cross-section of tungsten irradiated by 20 MeV W6+ ions

Fatigue Tests and Metallographic of Explosively Cladded Steel-Titanium Bimetal/ Badania Zmęczeniowe I Metalograficzne Bimetalu Stal-Tytan Zgrzewanego Wybuchowo

The paper contains a description of fatigue life tests of titan-steel bimetal. The study involved specimens made of bimetal which was a combination of S355J2 steel and SB G1 265 titanium, which was imposed in the material by explosive cladding method. The research shows that the fatigue life of specimens made of native material, derived from cladded plate is less than the life of specimens of titanium-steel bimetalW pracy zawarto wyniki badań zmęczeniowych i metalograficznych bimetalu będącego połączeniem stali S355J2 z tytanem SB265G1 przy pomocy technologii zgrzewania wybuchowego. Analiza wyników badań dowodzi, że proces zgrzewania wybuchowego i obróbki cieplnej mają wpływ na trwałość zmęczeniowa materiału. Ponadto stwierdzono, że w procesie projektowania elementów narażonych na zmiennę obciążenia należy uwzględnić własności wszystkich materiałów wchodzących w skład plateru

Microstructure and fatigue life of Cp-Ti/316L bimetallic joints obtained by means of explosive welding

This paper describes a study of explosively welded, commercially pure titanium-stainless steel 316L plates. Following welding, the plates were heat-treated at the temperature of 600°C for 90 minutes. Examinations of the bond structure were carried out before and after heat treatment to investigate the processes taking place during explosive welding of materials. Observations were performed using light, scanning electron (SEM) and transmission electron microscopy (TEM). The mechanical properties were examined applying three-point bending tests with cyclic loads. Fractographic examination and hardness measurements were also performed. It has been found that the bonding zones are characterized by a specific microstructure, chemical composition and microhardness. The heat treatment used in the study increases the relative volume of brittle intermetallic phases, causing a reduction in fatigue strength of the joint

Badania zmęczeniowe i metalograficzne bimetalu stal-tytan zgrzewanego wybuchowo

The paper contains a description of fatigue life tests of titan-steel bimetal. The study involved specimens made of bimetal which was a combination of S355J2 steel and SB G1 265 titanium, which was imposed in the material by explosive cladding method. The research shows that the fatigue life of specimens made of native material, derived from cladded plate is less than the life of specimens of titanium-steel bimetalW pracy zawarto wyniki badań zmęczeniowych i metalograficznych bimetalu będącego połączeniem stali S355J2 z tytanem SB265G1 przy pomocy technologii zgrzewania wybuchowego. Analiza wyników badań dowodzi, że proces zgrzewania wybuchowego i obróbki cieplnej mają wpływ na trwałość zmęczeniowa materiału. Ponadto stwierdzono, że w procesie projektowania elementów narażonych na zmiennę obciążenia należy uwzględnić własności wszystkich materiałów wchodzących w skład plateru

Advanced materials characterization and modeling using synchrotron, neutron, TEM, and novel micro-mechanical techniques - A European effort to accelerate fusion materials development

For the realization of fusion as an energy source, the development of suitable materials is one of the most critical issues. The required material properties are in many aspects unique compared to the existing solutions, particularly the need for necessary resistance to irradiation with neutrons having energies up to 14 MeV. In addition to withstanding the effects of neutrons, the mechanical stability of structural materials has to be maintained up to high temperatures. Plasma-exposed materials must be compatible with the fusion plasma, both with regard to the generation of impurities injected into the plasma and resistance to erosion and hydrogen isotope retention. The development of materials fulfilling these and other criteria is a large-scale and long-term activity which involves basic materials science, materials development, characterization under both loading conditions and off-line, as well as testing under neutron flux-induced conditions. For the realization of a DEMO power plant, the materials solutions must be available in time. The European initiative FEMaS-CA – Fusion Energy Materials Science – Coordination Action – aims at accelerating materials development by integrating advanced materials characterization techniques, among them the efficient use of neutron and synchrotron-based techniques, into the fusion materials community. Further, high-end transmission electron microscopy and mechanical characterization (also on a microscopic level in order to facilitate tests of small material volumes, such as from neutron irradiation campaigns) are to be more extensively applied in fusion materials research. Finally, irradiation facilities for neutron damage benchmarking are contributing to the understanding of radiation effects. This overview demonstrates by means of a few examples the recent advancements in fusion materials research, e.g. by applying synchrotron X-ray and neutron tomography to novel materials and components. Deeper understanding of radiation effects is achieved by in situ TEM of materials under irradiation. Modeling of irradiation effects is closely linked to activities at irradiation facilities. Finally, new developments in mechanical testing on micro- and nano-scales are addressed

Damage mechanisms of MoN/SiN multilayer optics for next-generation pulsed XUV light sources

We investigated the damage mechanism of MoN/SiN multilayer XUV optics under two extreme conditions: thermal annealing and irradiation with single shot intense XUV pulses from the free-electron laser facility in Hamburg - FLASH. The damage was studied "post-mortem" by means of X-ray diffraction, interference-polarizing optical microscopy, atomic force microscopy, and scanning transmission electron microscopy. Although the timescale of the damage processes and the damage threshold temperatures were different (in the case of annealing it was the dissociation temperature of Mo2N and in the case of XUV irradiation it was the melting temperature of MoN) the main damage mechanism is very similar: molecular dissociation and the formation of N2, leading to bubbles inside the multilayer structure