38 research outputs found

    Microstructures and Phases in Electron Beam Additively Manufactured Ti-Al-Mo-Zr-V/CuAl9Mn2 Alloy

    No full text
    Electron beam additive manufacturing from dissimilar metal wires was used to intermix 5, 10 and 15 vol.% of Ti-Al-Mo-Z-V titanium alloy with CuAl9Mn2 bronze on a stainless steel substrate. The resulting alloys were subjected to investigations into their microstructural, phase and mechanical characteristics. It was shown that different microstructures were formed in an alloy containing 5 vol.% titanium alloy, as well as others containing 10 and 15 vol.%. The first was characterized by structural components such as solid solution, eutectic intermetallic compound TiCu2Al and coarse grains of Îł1-Al4Cu9. It had enhanced strength and demonstrated steady oxidation wear in sliding tests. The other two alloys also contained large flower-like Ti(Cu,Al)2 dendrites that appeared due to the thermal decomposition of Îł1-Al4Cu9. This structural transformation resulted in catastrophic embrittlement of the composite and changing of wear mechanism from oxidative to abrasive

    In-Situ Al-Mg Alloy Base Composite Reinforced by Oxides and Intermetallic Compounds Resulted from Decomposition of ZrW<sub>2</sub>O<sub>8</sub> during Multipass Friction Stir Processing

    No full text
    In the presented work, the effect of friction stir processing admixing the zirconium tungstate ZrW2O8 powder on the microstructure, mechanical and tribological properties of the AA5056 Al-Mg alloy stir zone has been studied. The FSP resulted in obtaining dense composite stir zones where α-ZrW2O8 underwent the following changes: (i) high-temperature transformation into metastable β’-ZrW2O8 and (ii) decomposition into WO3 and ZrO2 oxides followed by the formation of intermetallic compounds WAl12 and ZrAl3. These precipitates served as reinforcing phases to improve mechanical and tribological characteristics of the obtained fine-grained composites. The reduced values of wear rate and friction coefficient are due to the combined action the Hall–Petch mechanism and reinforcement by the decomposition products, including Al2O3, ZrO2, β’-ZrW2O8 and intermetallic compounds such as WAl12 and ZrAl3. Potential applications of the above-discussed composites maybe related to their improved tribological characteristics, for example in aerospace and vehicle-building industries

    Intense Locomotion Enhances Oviposition in the Freshwater Mollusc <i>Lymnaea stagnalis</i>: Cellular and Molecular Correlates

    No full text
    Intense species-specific locomotion changes the behavioural and cognitive states of various vertebrates and invertebrates. However, whether and how reproductive behaviour is affected by previous increased motor activity remains largely unknown. We addressed this question using a model organism, the pond snail Lymnaea stagnalis. Intense crawling in shallow water for two hours had previously been shown to affect orienting behaviour in a new environment as well as the state of the serotonergic system in L. stagnalis. We found that the same behaviour resulted in an increased number of egg clutches and the total number of eggs laid in the following 24 h. However, the number of eggs per clutch was not affected. This effect was significantly stronger from January to May, in contrast to the September–December period. Transcripts of the egg-laying prohormone gene and the tryptophan hydroxylase gene, which codes for the rate-limiting enzyme in serotonin synthesis, were significantly higher in the central nervous system of snails that rested in clean water for two hours after intense crawling. Additionally, the neurons of the left (but not the right) caudo-dorsal cluster (CDC), which produce the ovulation hormone and play a key role in oviposition, responded to stimulation with a higher number of spikes, although there were no differences in their resting membrane potentials. We speculate that the left–right asymmetry of the response was due to the asymmetric (right) location of the male reproductive neurons having an antagonistic influence on the female hormonal system in the hermaphrodite mollusc. Serotonin, which is known to enhance oviposition in L. stagnalis, had no direct effect on the membrane potential or electrical activity of CDC neurons. Our data suggest that (i) two-hour crawling in shallow water enhances oviposition in L. stagnalis, (ii) the effect depends on the season, and (iii) the underlying mechanisms may include increased excitability of the CDC neurons and increased expression of the egg-laying prohormone gene

    Structure, Mechanical Properties and Friction Characteristics of the Al-Mg-Sc Alloy Modified by Friction Stir Processing with the Mo Powder Addition

    No full text
    In this study, samples of Al-Mg-Sc alloy were investigated after friction stir processing with the addition of Mo powder. Holes were drilled into 5 mm-thick aluminum alloy sheets into which Mo powder was added at percentages of 5, 10, and 15 wt%. The workpieces with different powder contents were then subjected to four passes of friction stir processing. Studies have shown that at least three tool passes are necessary and sufficient for a uniform Mo powder distribution in the stir zone, but the number of required passes is higher with an increase in the Mo content. Due to the temperature specifics of the processing, no intermetallic compounds are formed in the stir zone, and Mo is distributed as separate particles of different sizes. The average ultimate strength of the composite materials after four passes is approximately 387 MPa in the stir zone, and the relative elongation of the material changes from 15 to 24%. The dry sliding friction test showed that the friction coefficient of the material decreases with the addition of 5 wt% Mo, but with a further increase in Mo content, returns to the original material values

    Development of a Multimaterial Structure Based on CuAl<sub>9</sub>Mn<sub>2</sub> Bronze and Inconel 625 Alloy by Double-Wire-Feed Additive Manufacturing

    No full text
    This work studied the possibility of producing multimaterials consisting of aluminum bronze CuAl9Mn2 and nickel-based superalloy Inconel 625 by double-wire electron beam additive manufacturing. Samples with 5%, 15%, 25%, and 50% of the nickel-based alloy in aluminum bronze were produced for the research. The structural features of these multimaterials were analyzed, and tensile properties, microhardness, and dry sliding friction properties were measured. The results showed that 50% of the nickel-based alloy in the multimaterial composition provides the formation of a dendritic structure. Such a material shows worse values of ductility and wear resistance. Samples containing 5%, 15%, and 25% of Inconel 625 provide similar friction coefficient values, whereas, with increasing concentration of the nickel-based alloy, the material’s ultimate tensile strength and microhardness increase significantly

    Features of Microstructure and Texture Formation of Large-Sized Blocks of C11000 Copper Produced by Electron Beam Wire-Feed Additive Technology

    No full text
    The paper investigated the possibility of obtaining large-sized blocks of C11000 copper on stainless steel substrates via electron beam wire-feed additive technology. The features of the microstructure and grain texture formation and their influence on the mechanical properties and anisotropy were revealed. A strategy of printing large-sized C11000 copper was determined, which consists of perimeter formation followed by the filling of the internal layer volume. This allows us to avoid the formation of defects in the form of drops, underflows and macrogeometry disturbances. It was found that the deposition of the first layers of C11000 copper on a steel substrate results in rapid heat dissipation and the diffusion of steel components (Fe, Cr and Ni) into the C11000 layers, which promotes the formation of equiaxed grains of size 8.94 &plusmn; 0.04 &mu;m. As the blocks grow, directional grain growth occurs close to the &lt;101&gt; orientation, whose size reaches 1086.45 &plusmn; 57.13 &mu;m. It is shown that the additive growing of large-sized C11000 copper leads to the anisotropy of mechanical properties due to non-uniform grain structure. The tensile strength in the opposite growing direction near the substrate is 394 &plusmn; 10 MPa and decreases to 249 &plusmn; 10 MPa as the C11000 blocks grows. In the growing direction, the tensile strength is 145 &plusmn; 10 MPa

    Characterizing the Tensile Behavior of Double Wire-Feed Electron Beam Additive Manufactured &ldquo;Copper&ndash;Steel&rdquo; Using Digital Image Correlation

    No full text
    The paper presents the results of the evaluation of the mechanical characteristics of samples of multi-metal &ldquo;copper-steel&rdquo; structures fabricated by additive double wire electron beam method. The global and local mechanical characteristics were evaluated using uniaxial tensile tests and full-field two-dimensional digital image correlation (DIC) method. DIC revealed the peculiarities of the fracture stages: at the first stage (0.02&lt;&epsilon;&le;0.08) the formation of V-shaped shear lines occurs; at the second stage (0.08&lt;&epsilon;&le;0.15) transverse shear lines lead to the formation of a block structure; at the third stage (0.15&lt;&epsilon;&le;0.21) the plasticity resource ends in the central part of the two necks cracks are formed, and the main crack is the cause of the fracture of the joint. It is found that shear lines are formed first in copper and then propagate to steel. Electron microscopy proves that uniformly distributed iron particles could always be found in the &ldquo;Fe-Cu&rdquo; and &ldquo;Cu-Fe&rdquo; interfaces. Additionally, the evolution of average strain rates and standard deviations were measured (calculated) in the regions of necks in copper and steel regions. New shear approach shows that the most of angles for parallel shears components are &plusmn;45&deg;, rupture angles are about 0&deg;, and combined account of these two types of shears provides us additional discrete angles

    Dry Sliding Friction Study of ZrN/CrN Multi-Layer Coatings Characterized by Vibration and Acoustic Emission Signals

    No full text
    In this work, we studied single-layer ZrN and CrN coatings, as well as multi-layer ZrN/CrN coatings deposited by the vacuum-arc method on WC-8 wt.% Co substrates. The sliding friction parameters were preset to simulate different operating conditions for coatings, i.e., severe and zero wear regimes. During the tests, the friction coefficient, acoustic emission (AE) and vibration signals were recorded. After testing, the worn surfaces of the samples were studied using confocal laser scanning and scanning electron microscopy, elemental microanalysis and synchrotron XRD. Estimation of vibration accelerations and AE energy turned out to be very effective means of monitoring the wear of coatings, while median AE frequency turned out to be a less informative one. With the increase in the normal load applied on the samples after testing at zero wear regime, the coefficient of friction increased and wear transition to severe wear regime occurred but vibration acceleration decreased. The multi-layer ZrN/CrN coatings demonstrated much higher wear resistance as compared to those of single-layer ZrN and CrN

    High-Temperature Oxidation of CrN/ZrN Multilayer Coatings

    No full text
    Multilayer nitride coatings provide some of the best performance when in their use for the production of metalworking tools. In this work, vacuum-arc plasma-assisted deposited multilayer ZrN/CrN coatings with different numbers of constituent layers were characterized for high-temperature oxidization in air using weighing, confocal and scanning electron microscopy and synchrotron XRD. Oxidizing at 300 &deg;C did not deteriorate the coating surfaces, while higher temperatures caused surface deterioration and oxidation accompanied by cracking, delamination and considerable mass gains. The coating with higher number of thinner layers showed higher oxidation resistance due to more prominent oxygen barrier effect

    Microstructural Evolution of AA5154 Layers Intermixed with Mo Powder during Electron Beam Wire-Feed Additive Manufacturing (EBAM)

    No full text
    AA5154 aluminum alloy wall was built using EBAM where the wall’s top layers were alloyed by depositing and then remelting a Mo powder-bed with simultaneous transfer of aluminum alloy from the AA5154 wire. The powder-beds with different concentrations of Mo such as 0.3, 0.6, 0.9 and 1.2 g/layer were used to obtain composite AA5154/Mo samples. All samples were characterized by inhomogeneous structures composed of as-deposited AA5154 matrix with coarse unreacted Mo articles and intermetallic compounds (IMC) such as Al12Mo, Al5Mo, Al8Mo3, Al18Mg3Mo2 which formed in the vicinity of these Mo particles. The IMC content increased with the Mo powder-bed concentrations. The AA5154 matrix grains away from the Mo particles contained Al-Fe grain boundary precipitates. Mo-rich regions in the 0.3, 0.6, 0.9 and 1.2 g/layer Mo samples had maximum microhardness at the level of 2300, 2600, 11,500 and 9000 GPa, respectively. Sliding pin-on-steel disk test showed that wear of A5154/Mo composite reduced as compared to that of as-deposited AA5154 due to composite structure, higher microhardness as a well as tribooxidation of Al/Mo IMCs and generation of mechanically mixed layers containing low shear strength Mo8O23 and Al2(MoO4)3 oxides
    corecore