Laser beam welding of a CoCrFeNiMn-type high entropy alloy produced by self-propagating high-temperature synthesis

Fiber laser beam welding of a CoCrFeNiMn-type high entropy alloy (HEA) produced by self-propagating hightemperature synthesis (SHS) was reported in this work. The SHS-fabricated alloy was characterized by both ∼2 times reduced Mn content in comparison with that of the other principal components and the presence of impurities including Al, C, S, and S

Laser beam welding of a Ti-15mo/TIB metal-matrix composite

A Ti-15Mo/TiB metal-matrix composite was produced by spark plasma sintering at 1400 °C. The fractions of the elements in the initial powder mixture were 80.75 wt.% Ti, 14.25 wt.% Mo, and 5 wt.% TiB2. The initial structure of the synthesized composite was composed of bcc titanium matrix and needle-like TiB reinforcements with an average thickness of 500 ∓ 300 n

Fatigue behaviour of a laser beam welded CoCrFeNiMn-type high entropy alloy

Laser beam welding was used to produce butt joints from the CoCrFeNiMn-type high entropy alloy. The alloy in the initial condition had an fcc single-phase coarse-grained structure. Laser welding resulted in the M7C3-type carbide particles precipitation resulted in a considerable increase in microhardness from 150 HV 0.5 for the as-sintered condition to 205 HV 0.5 in the fusion zone. Laser beam welding had a negligible effect on both static mechanical properties and fatigue behaviour of the allo

Позиционный электропривод механизма перемещения

Объектом исследования является позиционный асинхронный электропривод механизма горизонтального перемещения груза. Цель работы – исследовать основные характеристики асинхронного электропривода с трехконтурной системой управления положением вала двигателя. В процессе исследования проводились выбор асинхронного двигателя для механизма перемещения, расчет параметров двигателя, его статических и динамических характеристик, выбор преобразователя частоты, синтез трехконтурной системы управления следящим электроприводом на базе регулируемого с векторным управлением.The object of the study is a positional asynchronous electric drive mechanism for the horizontal movement of cargo. The purpose of the work is to investigate the basic characteristics of an asynchronous electric drive with a three-circuit control system for positioning the motor shaft. In the process of research, the choice of an asynchronous motor for the displacement mechanism, calculation of the engine parameters, its static and dynamic characteristics, choice of a frequency converter, synthesis of a three-circuit control system for a servomotor drive based on an adjustable vector control were made

Microstructural and mechanical characterization of diffusion bonded hybrid joints

Ti-alloys, particularly TiAl, are becoming attractive for the use in the production of high-temperature components such as turbine blades and exhaust valves, owing to their low density. However, these components may not be cost-effectively cast totally from TiAl alloys and casting defects may occur in investment casting of these complex parts. Other manufacturing technologies, such as machining, cannot be economically employed in these very hard and brittle materials. Production of bi-material or even multi-material TiAl components can therefore offer an alternative fabrication route provided that the joining and joint properties of these materials are well understood. In this study, the diffusion bondability and joint characteristics of TiAl and Ti-6Al-4V alloys were studied. These two different materials were joined by using various bonding parameters. Metallographic investigations were conducted for characterization of the interface region of these dissimilar joints. Furthermore, the mechanical behavior of the bond interface was evaluated by shear testing. Both results on the microstructural and mechanical characterization provided the optimum bonding conditions for the production of TiAl-Ti6Al4V hybrid joints

Estratigrafía y estructura de las unidades alpujárrides en el borde occidental de Sierra Nevada (Granada, España)

12 páginas, 5 figuras.[EN] The revision of the Alpujarride units in the west of Sierra Nevada shows that although the previous distinction of units was correct, their cartographic separation presented numerous omissions and errors. For this reason we described more precise stratigraphic sequences of the units, allowing the knowledge of new terms of the series in this sector, both in the lower unit (Rhaetian) and in the middle one (Carnian and Rhaetian). From the tectonic point of view, the former overthrust contacts among the alpujarride units are very affected by an important stage of gravity tectonics and the units are thinned largely, so much as nearer the Nevado-Filabride they are. This fact, produced by the strong uplift of Sierra Nevada, also caused locally abnormal superposition of the units. The age of these phenomena of tectonic sliding and thinning should be estimated from the Late Miocene onwards.[ES] La revisión de las unidades alpujárrides en el oeste de Sierra Nevada muestra que, aunque era correcta la distinción de unidades previamente existente, su separación cartográfica presentaba numerosas omisiones y errores. Por ello, se han establecido series estratigráficas más precisas de las unidades, lo que ha permitido poner de manifiesto la existencia de nuevos tramos estratigráficos hasta ahora no descritos en este sector, tanto en la unidad inferior (materiales del Retiense) como en la unidad media (del Carniense y también del Retiense). Se destaca así mismo que los primeros contactos de cabalgamiento entre las unidades alpujárrides se encuentran muy afectados por una importante etapa de tectónica gravitatoria que ha producido deslizamientos de las unidades, las cuales se acuñan grandemente, tanto más cuanto más cerca del Nevado-Filábride se sitúan. Esto, que es debido al fuerte levantamiento de Sierra Nevada, ha provocado además superposiciones anormales. La edad de estos fenómenos de deslizamiento y acuñamiento hay que situarla a partir del Mioceno superior.Este artículo es una contribución de los proyectos PB97-1267-C03-01 y PB97-1201 de la DGESIC y de los grupos RNM 0163 y RNM 0217 de la Junta de Andalucía.Peer reviewe

Investigation into properties of laser welded similar and dissimilar steel joints

Laser beam welding is currently used in the welding of steels, aluminium alloys, thin sheets, and dissimilar materials. This high power density welding process has unique advantages of cost effectiveness, deep penetration, narrow bead and heat affected zone (HAZ) widths, and low distortion compared to other conventional welding processes. However the metallurgical and mechanical properties of laser welds and the response of conventional materials to this new process are not yet fully established. The welding process may lead to drastic changes in the microstructure with accompanying effects on the mechanical properties and hence, on the performance of the joint. The thermal cycles associated with laser beam welding are generally much faster than those involved in the conventional are welding processes. This leads to the formation of a rather small weld zone that exhibits locally a high hardness in the case of C-Mn structural steels owing to the formation of martensite. It is currently difficult to determine the tensile properties (full stress-strain curves) of the laser welded joint area owing to the small size (similar to 2-3 mm) of the fusion zone. Complete information on the tensile and fracture toughness properties of the fusion zone is essential for prequalification and complete understanding of the joint performance in service as well as for conducting a defect assessment procedure on such welded joints. Therefore, an experimental investigation into the mechanical properties of laser welded joints was carried out to establish a testing procedure using flat microtensile specimens (0.5 mm in thickness, 2 mm in width) for determination of the tensile properties of the weld metal and HAZ of the laser beam welds. Three similar joints, namely St 37-St 37, St 52-St 52, and austenitic-austenitic, and two dissimilar ferritic-austenitic joints were produced by CO2 laser using 6 mm thickness plates. The mechanical properties have been examined by microhardness survey and testing of conventional transverse tensile, round tensile, and flat microtensile specimens. The results for the microtensile specimens were compared with those for standard round tensile specimens and this clearly showed the suitability of the microtensile specimen technique for such joints

Charakterisierung diffusionsgeschweisster Titanaluminide

Special print from: Schweissen und Schneiden, v. 49(9), 1997, p. 660-671Available from TIB Hannover: RA 3251(97/E/58) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman