Laser Cladding and Additive Manufacturing Technologies Using High-Entropy, Ceramic and Multilayer Materials

Рассмотрено получение теплостойких покрытий и деталей из высокоэнтропийных сплавов лазерными наплавкой и выращиванием. Высокоскоростным селективным лазерным плавлением создаются сверхтвердые покрытия на основе карбида и нитрида бора. Предложена комбинированная постобработка изделий аддитивного производства с формированием многослойных тонкопленочных покрытий.The review considers the production of heat-resistant coatings and parts from high-entropy alloys by laser cladding and additive manufacturing. High-speed selective laser melting creates superhard coatings based on boron carbide and boron nitride. A combined post-processing of additive manufacturing products with the formation of multilayer thin-film coatings is proposed.Работа выполнена в рамках государственных заданий ИФМ УрО РАН по теме № АААА-А18-118020190116-6 и ИМАШ УрО РАН по теме № АААА-А18-118020790147-4 при поддержке гранта РФФИ № 20-48­660065 и Свердловской области в части постобработки деталей аддитивного производства с формированием тонкопленочного покрытия. Исследование также поддержано проектом № IRA-SME‑66316 «cladHEA+» по программе M‑ERA. NET, Call 2019‑II в части получения покрытий из высокоэнтропийных сплавов лазерной наплавкой.The work was carried out within the framework of the state tasks of the IFM of the Ural Branch of the Russian Academy of Sciences on the topic no. AAAA18–118020190116–6 and IMASH of the Ural Branch of the Russian Academy of Sciences on the topic no. AAAA18-118020790147-4 with the support of the RFBR grant no. 20-48-660065 and the Sverdlovsk region in terms of post-processing of additive manufacturing parts with the formation of thin-film coating. The research is also supported by the project No. IRA-SME‑66316 “cladHEA+” under the program M‑ERA. NET, Call 2019‑II in terms of obtaining coatings from high-entropy alloys by laser surfacing

Discovery of a Luminous Radio Transient 460 pc from the Central Supermassive Black Hole in Cygnus A

We report the appearance of a new radio source at a projected offset of 460 pc from the nucleus of Cygnus A. The flux density of the source (which we designate Cygnus A-2) rose from an upper limit of <0.5 mJy in 1989 to 4 mJy in 2016 (ν = 8.5 GHz), but is currently not varying by more than a few percent per year. The radio luminosity of the source is comparable to the most luminous known supernovae, it is compact in Very Long Baseline Array observations down to a scale of 4 pc, and it is coincident with a near-infrared point source seen in pre-existing adaptive optics and HST observations. The most likely interpretation of this source is that it represents a secondary supermassive black hole in a close orbit around the Cygnus A primary, though an exotic supernova model cannot be ruled out. The gravitational influence of a secondary SMBH at this location may have played an important role in triggering the rapid accretion that has powered the Cygnus A radio jet over the past 107 years

Tidal disruption rates in non-spherical galactic nuclei formed by galaxy mergers

We explore the rates of tidal disruption events (TDEs) of stars by supermassive black holes (SBHs) in galactic nuclei formed in mergers followed by a formation and coalescence of a binary SBH. Such systems initially have a deficit of stars on low-angular-momentum orbits caused by the slingshot process during the binary SBH stage, which tends to reduce the flux of stars into the SBH compared to the steady-state value. On the other hand, a newly formed galactic nucleus has a non-spherical shape which enhances the mixing of stars in angular momentum and thus the TDE rate. In galaxies with relatively low SBH masses (&lt;107M.), relaxation times are short enough to wash out the anisotropy in initial conditions, and for more massive SBH the enhancement of flux due to non-sphericity turns out to be more important than its suppression due to initial anisotropy. Therefore, the present-day TDE rates generally exceed conventional steady-state estimates based on a spherical isotropic approximation. We thus conjecture that the lower observationally inferred TDE rates compared to theoretical predictions cannot be attributed to the depletion of low-angular-momentum stars by SBH binaries