THE OPTIMISATION OF LASER WELDING PROCESS PARAMETERS OF 7020 ALUMINIUM ALLOY

В работе изучено влияние технологических параметров процесса лазерной сварки на геометрию сварного шва, включая грублину и ширину, а также влияние соотношения различных параметров, например, мощность лазерного пучка и скорость его движения.Laser welding has been proven to be promising for the aerospace industry. Welds with high aspect ratio are produced with lower heat input compared with conventional welding is given, combining the trials with Nd:YAG laser and existing knowledge in the referred literature. In this work, we studied the effect of process parameters on weld profile geometry including penetration depth and width on top surfaces and interfaces as well as its quality at different process parameters such as Laser power and speed.The work was performed as part of the state work "Carrying out of research work (basic research, applied research and experimental development)" state task MES of Russia in the sphere of scientific activities 2014-2016. (Task № 2014/113)

Evaluation of the microstructure and mechanical properties of a new modified cast and laser-melted AA7075 alloy

The mechanical properties and microstructure of as-cast and homogenized AA7075 were investigated. This alloy was modified by adding transition elements 0.3%Sc + 0.5%Zr, 1%Ti + 0.2%B, and 1%Fe + 1%Ni for use in additive manufacturing applications. After adding Ti + B and Sc + Zr, the structure became uniform and finer with the formation of the Al3(Sc, Zr) and TiB2 phases. Coarse structures were obtained with the formation of an extremely unfavorable morphology, close to a needle-like structure when Fe + Ni was added. The mechanical properties of the modified alloys were increased compared to those of the standard alloy, where the best ultimate tensile strength (UTS) and yield strength (YS) were obtained in the AA7075-TiB alloy compared to the standard alloy in as-cast and homogenized conditions, and the highest hardness value was provided by Fe + Ni additives. The effect of the laser melting process on the microstructure and mechanical properties was investigated. Single laser melts were performed on these alloys using 330 V and a scanning speed of 8 mm/s. During the laser melting, the liquation of the alloying elements occurred due to non-equilibrium solidification. A change in the microstructures was observed within the melt zone and heat-affected zone (HAZ). The hardness of the laser-melted zone (LMZ) after adding the modification elements was increased in comparison with that of the standard alloy. Corrosion testing was performed using a solution of 100 mL distilled water, 3.1 g NaCl, and 1 mL HCl over 5, 10, and 30 min and 1 and 2 h. The corrosion resistance of the alloy modified with FeNi was low because of the non-uniform elemental distribution along the LMZ, but in the case of modification with ScZr and TiB, the corrosion resistance was better compared to that of the standard alloy. © 2019 by the authors.Ministry of Science and Higher Education of the Russian FederationThe author (Asmaa M. Khalil) gratefully acknowledges financial support from the Ministry of Science and Higher Education of the Russian Federation in the framework of Increase Competitiveness Program of MISiS (Support project for young research engineers)

Influence of Adding Modifying Elements and Homogenization Annealing on Laser Melting Process of the Modified Alznmgcu with 4%si Alloys

AlZnMgCu, the high-strength aluminum alloy, is unsuitable for laser melting applications due to its high hot cracking sensitivity and large solidification temperature range. Adapting this alloy for laser melting processing is a high-demand research issue for extending its use. Thus, this paper investigates the effect of adding 4%Si, 4%Si-Sc + Zr, 4%Si-Ti + B, and homogenization annealing on the laser melting process (LMP) of AlZnMgCu alloy. Homogenization annealing at 500◦ C for 6.5 h was selected to dissolve most of the low melting temperature phases into the grain matrix and perform stable alloys for the LMP. The pulsed laser melting process (PLM) was performed on the as-casted and the homogenized samples. The microstructures of the as-casted, the homogenized alloys, and after the LMP were evaluated. In addition, the hardness of the base metal (BM) and laser melted zone (LMZ) were measured. The results revealed that the microstructure was enhanced and refined in the as-cast state by adding the modifiers due to the increasing nucleation potency of solidification sites and the formation of primary Al3 (Ti, Zr, Sc) phases. The average grain size was decreased by 15.6 times when adding 4%Si + 0.4%Zr + 0.29%Sc, while it decreased by 10.2 times when adding 4%Si + 1%Ti + 0.2%B. The LMZ of the as-casted samples exhibited a non-uniform distribution of the grains and the elements after the LMP. This was attributed to the evaporation of Zn, Mg during the high laser power process besides the non-uniform distribution of elements and phases in samples during casting. After the laser treating of the homogenized samples with 4%Si-Sc + Zr, uniform columnar grains were formed in the direction of the laser. The presence of Ti and B changed the crystallization nature, resulting in the LMZ with very fine and equiaxed grains due to forming many nucleation centers during solidification. The hardness values have positively increased due to Si addition and adding a combination of Ti + B and Sc + Zr. The maximum hardness was 153.9 ± 5 HV achieved in the LMZ of the homogenized samples of 4%Si + 1%Ti + 0.2%B. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Funding: This research was partially funded by Russian Foundation for Basic Research (RFBR) with project number 19-38-60037

Features of Structure Formation in an Al–Fe–Mn Alloy upon Crystallization with Various Cooling Rates

Abstract: Specific features of the microstructure formation of an Al–2.5% Fe–1.5% Mn alloy owing to the cooling rate during casting and during laser melting are studied in this work. An analysis of the microstructure in the molten state shows that, with an increase in the cooling rate during crystallization from 0.5 to 940 K/s, the primary crystallization of the Al6(Mn,Fe) phase is almost completely suppressed and the volume of the nonequilibrium eutectic increases to 43%. The microstructures of the Al–2.5% Fe–1.5% Mn alloy after laser melting are characterized by the presence of crystals of an aluminum matrix of a dendritic type with an average cell size of 0.56 μm, surrounded by an iron-manganese phase of eutectic origin with an average plate size of 0.28 μm. The primary crystallization of the Al6(Mn,Fe) phase is completely suppressed. The formation of such a microstructure occurs at cooling rates of 1.1 × 104–2.5 × 104 K/s, which corresponds to the cooling rates implemented in additive technologies. At the boundary between the track and the base metal and between the pulses, regions were revealed consisting of primary crystals of the Al6(Mn,Fe) phase formed by the epitaxial growth mechanism. The size of the primary crystals and the width of this zone depends on the size of the eutectic plates and the size of the dendritic cell located in the epitaxial layer. After laser melting, the Al–2.5% Fe–1.5% Mn alloy has a high hardness at room temperature (93 HV) and, after heating up to 300°C, it has a high thermal stability (85 HV). The calculated yield strength of the Al–2.5% Fe–1.5% Mn alloy after laser melting is 227 MPa. The combination of its ultrafine microstructure, high processibility during laser melting, hardness at room and elevated temperatures, and high calculated yield strength make the Al–2.5% Fe–1.5% Mn alloy a promising alloy for use in additive technologies. © 2021, Allerton Press, Inc

Factors influencing the prevalence of resistance-associated substitutions in NS5A protein in treatment-naive patients with chronic hepatitis C

Direct-acting antivirals (DAAs) revolutionized treatment of hepatitis C virus (HCV) infection. Resistance-associated substitutions (RASs) present at the baseline impair response to DAA due to rapid selection of resistant HCV strains. NS5A is indispensable target of the current DAA treatment regimens. We evaluated prevalence of RASs in NS5A in DAA-naïve patients infected with HCV 1a (n = 19), 1b (n = 93), and 3a (n = 90) before systematic DAA application in the territory of the Russian Federation. Total proportion of strains carrying at least one RAS constituted 35.1% (71/202). In HCV 1a we detected only M28V (57.9%) attributed to a founder effect. Common RASs in HCV 1b were R30Q (7.5%), L31M (5.4%), P58S (4.4%), and Y93H (5.4%); in HCV 3a, A30S (31.0%), A30K (5.7%), S62L (8.9%), and Y93H (2.2%). Prevalence of RASs in NS5A of HCV 1b and 3a was similar to that worldwide, including countries practicing massive DAA application, i.e., it was not related to treatment. NS5A with and without RASs exhibited different co-variance networks, which could be attributed to the necessity to preserve viral fitness. Majority of RASs were localized in polymorphic regions subjected to immune pressure, with selected substitutions allowing immune escape. Altogether, this explains high prevalence of RAS in NS5A and low barrier for their appearance in DAA-inexperienced population.Fil: Kyuregyan, Karen K.. Russian Academy Of Sciences; Rusia. Russian Medical Academy Of Continuous Professional Education; Rusia. I. I. Mechnikov Research Institute For Vaccines And Sera; RusiaFil: Kichatova, Vera S.. Russian Medical Academy Of Continuous Professional Education; Rusia. Russian Academy Of Sciences; Rusia. I. I. Mechnikov Research Institute For Vaccines And Sera; RusiaFil: Karlsen, Anastasiya A.. I. I. Mechnikov Research Institute For Vaccines And Sera; Rusia. Russian Medical Academy Of Continuous Professional Education; Rusia. Russian Academy Of Sciences; RusiaFil: Isaeva, Olga V.. I. I. Mechnikov Research Institute For Vaccines And Sera; Rusia. Russian Medical Academy Of Continuous Professional Education; RusiaFil: Solonin, Sergei A.. N.V. Sklifosovsky Research Institute for Emergency Medicine; RusiaFil: Petkov, Stefan. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Nielsen, Morten. Technical University of Denmark; Dinamarca. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Isaguliants, Maria G.. Russian Academy Of Sciences; Rusia. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Mikhailov, Mikhail I.. Russian Medical Academy Of Continuous Professional Education; Rusia. I. I. Mechnikov Research Institute For Vaccines And Sera; Rusi

Evaluation of Microstructure and Hardness of Novel Al-Fe-Ni Alloys with High Thermal Stability for Laser Additive Manufacturing

The microstructure and phase composition of cast and laser-melted Al-Fe-Ni alloys were investigated.Two main phases—Al3(Ni,Fe) and Al9FeNi—were formed in the as-cast state. A fine microstructure without porosity or solidification cracks was observed in the Al-Fe-Ni alloys after laser treatment. The hardness of the laser-melted alloys was 2.5–3 times higher than the hardness of the as-cast alloys owing to the formation of an aluminum-based solid solution and fine eutectic particles. The formation of the primary Al9FeNi phase was suppressed as a result of the high cooling rate. Annealing these alloys at temperatures less than 300°C demonstrated the high thermal stability of the microstructure while maintaining the hardness. The Al-Fe-Ni alloys investigated in this study are promising heat-resistant materials for additive manufacturing because of their fine, stable structure, and the low interdiffusion coefficients of Fe and Ni. © 2020, The Minerals, Metals & Materials Society.Loginova I.S. would like to thank Dr. Solonin A.N. for valuable discussions regarding the structure formation process. This project and all the experiments were funded by RFBR, Project Number 19-38-60037

Влияние Zr, Sc, Ti, B Fe и Ni на микроструктуру сплава aa7075 при лазерной обработке

In the present work the wrought aluminium alloy AA7075 modified with 0,3%Sc+0,5%Zr, 1%Тi+0,2 %B and 1%Fe+1%Ni to refine and uniform the grain structure, to decrease the effective solidification range to decrease the hot crack formation during rapid solidification after laser processing was studied.В настоящей работе исследован высокопрочный сплав AA7075, дополнительно легированный 0,3%Sc+0,5%Zr, 1%Ti+0,2%B и 1%Fe+1%Ni для повышения сопротивляемости сплава образованию горячих трещин и однородности структуры

ПРОБЛЕМЫ ОБЕСПЕЧЕНИЯ ИНФЕКЦИОННОЙ БЕЗОПАСНОСТИ ОРГАННОГО И ТКАНЕВОГО ДОНОРСТВА ПРИ ЛАБОРАТОРНОЙ ДИАГНОСТИКЕ ГЕМОКОНТАКТНЫХ ВИРУСНЫХ ИНФЕКЦИЙ

It provided data on the prevalence, clinical signifi cance and methods of laboratory diagnostics for occult forms of blood-borne viral infections (BBVIs). It considered causes of such forms of infection and their signifi cance for clinical transplantation. We analyzed the existing algorithm of laboratory screening of a potential organ donor for BBVIs in Russia. It is shown that the current screening algorithm doesn’t allow detecting hidden forms of BBVIs.Представлены данные о распространенности, клинической значимости и методах лабораторной диагностики скрытых форм гемоконтактных вирусных инфекций (ГВИ). Рассмотрены причины возникновения таких форм инфекции и их значимость для клинической трансплантологии. Проанализирован существующий алгоритм лабораторного обследования потенциального донора органов на ГВИ в РФ. Показано, что действующий алгоритм скрининга доноров на ГВИ не позволяет выявлять скрытые формы инфекции

СТРУКТУРА ОБРАЩЕНИЙ ПАЦИЕНТОВ СО СМЕШАННЫМИ ФОРМАМИ ГЕМОКОНТАКТНЫХ ВИРУСНЫХ ИНФЕКЦИЙ В МНОГОПРОФИЛЬНОМ СТАЦИОНАРЕ

We retrospectively analyzed the number and causes of hospitalizations in patients with mixed types of blood-borne viral infections (BBVIs) in specialized departments of a general hospital in 2010– 2014. We revealed an increase in detection of mixed BBVIs from 1.39 up to 1.50% (χ2 =1.192, df=1, p>0.05), particularly hIV/hCV and hIV/hBV/hCV. The majority of patients with co-infections had different medical and social deviations. The highest incidence of mixed infection occurred among men, mainly in the age group of 31–40 years (χ2 =5.46, df=1, p<0.05). Departments with the highest degree of the epidemic hazard for transmission of mixed BBVIs were the department of intensive care and resuscitation with a small operating room for emergency detoxification, departments of acute poisoning for the mentally ill patients, the department of resuscitation and intensive care for emergency patients and somato-psychiatric department.Ретроспективно проанализирована динамика количества и причин госпитализации пациентов с микст-формами гемоконтактных вирусных инфекций (ГВИ) в специализированные отделения стационара общесоматического профиля за период с 2010 по 2014 г. Зафиксирован рост выявляемости сочетанных форм инфекций с 1,39 до 1,50% (χ2 =1,192, df=1, p>0,05), преимущественно HIV+HCV и HIV+HBV+HCV. Большинство пациентов с сочетанными формами инфекций имели разного рода медико-социальные девиации. Наибольшая частота встречаемости микст-инфекций зафиксирована у мужчин, преимущественно в возрастной группе 31–40 лет (χ2 =5,46, df=1, p<0,05). К подразделениям с высокой степенью эпидемической опасности распространения микст-форм ГВИ относились: отделение реанимации и интенсивной терапии с малой операционной для экстренной детоксикации, отделения острых отравлений для психических больных, отделение реанимации и интенсивной терапии для экстренных больных, а также соматопсихиатрическое отделение

Structural and Phase Transformations in Al–Fe–Ni Alloy during Local Laser Exposure in Additive Technology

В ходе исследования были изучены микроструктура и фазовый состав сплавов Al–Fe–Ni в литом состоянии и после лазерного плавления. После лазерной обработки в сплавах Al–Fe–Ni формировалась тонкая дендритная микроструктура без пористости и кристаллизационных трещин. Твердость сплавов лазерной обработки была в 2,5–3 раза выше твердости литых сплавов за счет образования твердого раствора на основе алюминия и мелких эвтектических частиц.In the course of the study, the microstructure and phase composition of Al–Fe–Ni alloys in the cast state and after laser melting were studied. After laser melting, a thin dendritic microstructure without porosity and crystallization cracks was formed. The hardness of laser-treated alloys was 2,5–3 times higher than in cast alloys due to formation of aluminium-based solid solution and fine eutectic particles.Исследование выполнено при финансовой поддержке РФФИ в рамках научного проекта (№ 19–38–60037).The research was carried out with the financial support of the RFBR as part of a scientific project (№ 19–38–60037)