Production Of Alloys Research Articles

Swift and Cost-Effective Detection of Nitrite in Environmental Samples Using Ru@Pt Modified PGE

The development of a straightforward method is crucial for detecting and quantifying nitrite ions within the surrounding environment. This study involves the electrochemical fabrication of a bi-metallic alloy composed of Ruthenium and Platinum on a graphene-modified pge, the first-ever electrodeposition on pencil graphite (RuNPs@PtNPs/Gr-CHI). This study aims to establish a highly responsive and specific approach for identifying nitrite ions while demonstrating the efficacy of a commercially available pencil graphite electrode in detecting this environmental contaminant. The prevalence and structural characteristics of bimetallic nanoalloy particles are confirmed through X-ray diffraction, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The composite exhibited a core–shell shape at a size of 26.998 nm. The electrooxidation of nitrite at RuNPs@PtNPs/Gr-CHI/PGE was investigated using differential pulse voltammetry. The results demonstrated a satisfactory linear relationship from 0.025 mM to 1.625 mM. The method revealed a low detection limit of 0.33 μM. The composite electrode exhibited favorable outcomes regarding selectivity, sensitivity (25.5 μAμM−1cm−2), and repeatability, which are desirable characteristics of the electrochemical sensor material. The constructed electrode underwent testing for five weeks to determine the stability. The suggested sensor’s capability is demonstrated by detecting nitrite ions in real samples such as water, soil, and fruit juice.

CHARACTERIZATION OF ALUMINIUM METAL MATRIX COMPOSITES REINFORCED WITH SILICON CARBIDE AND NICKEL PARTICULATES

This research article presents the procedure for the fabrication of Aluminium alloy (LM25) based metal matrix composites containing particulates of silicon carbide (10 wt. %) and nickel (0, 5 and 10 wt. %). Using the vortex casting technique, three composites were formulated and characterized as per ASTM standards. Microstructure analysis using "scanning electron microscopy" reveals the uniform distribution of reinforcing particulates within the base matrix without clustering. "Energy dispersive spectroscopy" illustrates the presence of ingredients within the composites. "X-ray diffraction" patterns indicate the formation of mesoporous NiSiAl compound within the composite resulting from internal reactions. The "optical microscopy" reveals the refinement of grain structure with the inclusion of nickel particulates within the composites. The influence of the composition of reinforcing particulates that is, silicon carbide and nickel on the properties of the base matrix was explored. An enhancement in the microhardness, tensile strength, wear resistance and traction force and a reduction in friction coefficient was observed together with a marginal reduction in elongation and the porosity level is also under the controlled limits (<5%).

Effect of deformation degree on the mechanical properties of Al-Zn-Mg-Cu alloys: an industrial study

Abstract Hot deformation is a crucial process in the manufacturing of aluminum alloy products, as its parameters exert a profound influence on the ultimate properties of the alloys. This work reports on the Al-Zn-Mg-Cu alloys at a deformation temperature of 450°C, a deformation rate of 5 mm/s, and deformation degrees of 50% and 90% in industrial settings. Following that, an extensive assessment of the alloys’ mechanical characteristics, including their fracture toughness, tensile strength, and fatigue performance. Furthermore, a quantitative analysis of the microstructure was undertaken using OM and EBSD, which revealed that both the average and sub-grain sizes of the two alloys exhibited comparable characteristics. However, the recrystallization fraction showed a difference, with the alloy deformed to 90% exhibiting a higher fraction than the alloy deformed to 50%, while these recrystallized grains are distributed in chains. With the increase of deformation degree from 50% to 90%, the yield and ultimate strengths increase slightly. The opposite law is demonstrated by fatigue crack propagation resistance and fracture toughness. Put otherwise, compared to the alloy deformed to 50%, the alloy deformed to 90% exhibited a faster rate of fatigue crack propagation and a lower fracture toughness. In summary, this research examines how the degree of deformation affects the mechanical characteristics and microstructure of Al-Zn-Mg-Cu alloys.

Assessment of imaging performance for metal alloys of the first Italian neutron imaging beamline NICHE (Pavia, Italy)

In this paper, the imaging capabilities and performance of the new neutron imaging beamline developed at the LENA facility of Pavia (Italy) in the framework of the NICHE project (Neutron Imaging in Cultural HEritage) are presented. For this purpose, the estimation of bronze and brass alloys attenuation coefficient has been obtained through imaging analysis of a set of Cu-based alloy reference samples produced ad-hoc with chemical composition similar to ancient artefacts. In addition, some samples were realised using a different cooling ramp in order to test the influence of the alloy production procedures in neutron attenuation. Moreover, the tomographic capabilities of the beamline were tested for different metallic and plastic materials.

Investigation on in-situ tensile behaviors of 6061 aluminum alloy fabricated by wire additive friction stir deposition

Rod based additive friction stir deposition (R-AFSD) offers unique advantages for the integrated manufacturing of aluminum alloy near-net-shape large parts. However, the deposition process often faces issues like thick ends of raw material rods and difficulties in continuous feeding. In this study, wire based additive friction stir deposition (W-AFSD) was used for the solid state deposition of 3 mm diameter 6061 aluminum alloy wire. The microstructure evolution and mechanical properties of the deposit along the build direction were systematically characterized, clarifying the recrystallization mechanism and isotropy of the mechanical properties. In-situ scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) were used to study the deformation behavior of the deposit during in situ tensile testing, revealing a cooperative deformation mechanism involving grain rotation and intragranular slip. Results show that during in-situ tensile testing, the average rotation angle of five selected grains is 6.90°. Additionally, deposits with numerous grain boundaries due to recrystallization can hinder dislocation movement and pin the slip system within the grains during tensile testing. Due to the synergy of these mechanisms, the yield strengths of the longitudinal and transverse samples of the deposit are 183 MPa and 190 MPa, respectively, much higher than previously reported values. This article introduces a new solid state additive manufacturing method, offering new insights for efficient, high-strength continuous additive manufacturing of aluminum alloys and their deformation mechanisms.

IMPROVEMENT OF METHODS FOR DECOMPOSING MOLYBDENUM IN INDUSTRIAL PRODUCTS

The study of methods for extracting molybdenum into solutions from industrial ores and concentrates is an important task in the mining and metallurgical industry. Molybdenum (Mo) is used in the production of steel, alloys, electrode materials, and catalysts. The purpose of this work is to increase the efficiency of decomposition of molybdenum-containing materials, reduce production and processing costs, and minimize environmental impact. The tasks include the development of new chemical and metallurgical processes for processing various ores and concentrates, involving their decomposition and the extraction of molybdenum into a solution. Methodology. The study used microwave autoclave decomposition methods and chemical decomposition (acidic and fusion). The composition of the solution was determined using the atomic absorption method. The novelty of the research lies in the use of isolated microwave autoclave decomposition, which combines high efficiency and environmental safety. Results and discussion. The study compared the results obtained by the method of acidic decomposition and fusion in an open system with those from microwave autoclave decomposition in a closed system. Each method has its own advantages and disadvantages. The results of acidic and autoclave decompositions were similar to each other, while the results of fusion showed increased metal contents. The values of decomposition methods for standard copper and molybdenum concentrates showed results of 0.1-2.4%, respectively. The values of acidic (0.8%; 0.98%) and autoclave (0.9%; 1.04%) decompositions for samples from Chirchik and Stepnogorsk concentrates yielded similar results. Conclusion. The results of the decomposition methods of the materials do not differ significantly from each other from a production or industrial point of view. The analysis results can be applied in practice or used as reference values for scientific research.

The influence of anisotropy on the character of hardening in additive high-strength alloys

The purpose of this work is to establish the dependence of the coefficients of planar anisotropy on the intensity of localized deformations in various loading ranges of transverse and longitudinal sections of samples of heat-resistant powder alloy Inconel 718 manufactured using SLM technology. The role of technological anisotropy of samples characteristic of SLM technology and its effect on the hardening of Inconel 718 alloy products is evaluated. Methods. To achieve this goal, the deformation diagrams of Inconel 718 powder alloy samples manufactured using SLM technology, measured during their stretching according to GOST 11701-84, were analyzed. Flat samples with a dividing grid applied to their surface were subjected to loading. During the tests, localized deformation of the samples in different sections was determined by measuring the geometry of the images of the dividing grid. A specially developed photo and video recording technology was used to capture these images. Results. The statistical analysis of the type and parameters of the deformation diagrams made it possible to determine the nature of changes in the intensity of stresses and deformations of the samples of the studied material. The linear character of its tensile hardening in the region of small values of strain intensity and the power-law character of hardening in the range of strain intensity from 0.03 to 0.17 were established. Conclusion. A significant effect of the technological anisotropy of Inconel 718 heat-resistant powder alloy samples obtained using SLM technology on the intensity of deformations is shown. The necessity of taking this fact into account in the development of technological processes for the production of responsible products from the studied material has been revealed.

In-Situ Regulation to Tailor Additive Manufacturing of TiAl Alloy with Homogeneous Fine Fully Lamellar Colony

In-Situ Regulation to Tailor Additive Manufacturing of TiAl Alloy with Homogeneous Fine Fully Lamellar Colony

Effect of Hot Extrusion on Microstructure, Texture, and Mechanical Properties of Mg-Zn-Mn-0.5Ca Alloy

This paper investigates the microstructure, texture, and mechanical properties of the Mg-4Zn-1Mn-0.5Ca alloy subjected to hot extrusion under varying conditions of temperature (260 °C, 300 °C, 340 °C) and extrusion speed (0.01 mm/s, 0.1 mm/s, 1 mm/s). The primary objective is to determine the optimal extrusion parameters within the selected experimental range for achieving superior mechanical properties. The results indicate that, when extruded at a constant speed of 0.1 mm/s, the alloy exhibits optimal performance at 340 °C, with a yield strength of 202 MPa, ultimate tensile strength (UTS) of 306 MPa, and elongation at fracture of 18.9%. A decrease in extrusion temperature leads to an increase in yield strength but a reduction in ductility. Specifically, the UTS reaches its peak at 342 MPa at 300 °C, while it drops slightly to 329 MPa at 260 °C. The final results show that the comprehensive mechanical properties of the Mg-4Zn-1Mn-0.5Ca alloy obtained by hot extrusion treatment with an extrusion temperature of 300 °C and extrusion speed of 0.1 mm/s are the best and can effectively improve the mechanical properties of the alloy and provide a good choice for the preparation of other biodegradable magnesium alloy products.

Effect of Processing Route on Microstructure and Mechanical Properties of an Al-12Si Alloy.

Two different microstructures of an Al-12Si (wt. %) alloy were produced, respectively, via a powder laser bed fusion (P-LBF) additive manufacturing and casting. Compared to casting, additive manufacturing of Al-based alloy requires extra care to minimize oxidation tendency. The role of the microstructure on the mechanical properties of Al-12Si (wt. %) alloy was investigated by in situ compression of the micro-pillars. The microstructure of additively manufactured specimens exhibited a sub-cellular (~700 nm) nature in the presence of melt-pool arrangements and grain boundaries. On the other hand, the microstructure of the cast alloy contains typical needle-like eutectic structures. This striking difference in microstructure had obvious effects on the plastic flow of the materials under compression. The yield and ultimate compressive strength of the additively manufactured alloy were 23.69-27.94 MPa and 75.43-81.21 MPa, respectively. The cast alloy exhibited similar yield strength (31.46 MPa); however, its ultimate compressive strength (34.95 MPa) was only half that of the additively manufactured alloy. The deformation mechanism, as unrevealed by SEM investigation on the surface as well as on the cross-section of the distorted micro-pillars, confirms the presence of ductile and quasi-ductile facture of the matrix and the Si needle, respectively, in the case of the cast alloy. In contrast, the additively manufactured alloy exhibits predominantly ductile fractures.

Deep learning assisted femtosecond laser-ablation spark-induced breakdown spectroscopy employed for rapid and accurate identification of bismuth brass

BackgroundOwing to its excellent machinability and less toxicity, bismuth brass has been widely used in manufacturing various industrial products. Thus, it is of significance to perform rapid and accurate identification of bismuth brass to reveal the alloying properties. However, the analytical lines of various elements in bismuth brass alloy products based on conventional laser-induced breakdown spectroscopy (LIBS) are usually weak. Moreover, the analytical lines of various elements are often overlaped, seriously interfering with the identification of bismuth brass alloys. To address these challenges, developing an advanced strategy enabling to achieve ultra-high accuracy identification of bismuth brass alloys is highly desirable. ResultsThis work proposed a novel method for rapidly and accurately identifying bismuth brass samples using deep learning assisted femtosecond laser-ablation spark-induced breakdown spectroscopy (fs-LA-SIBS). With the help of fs-LA-SIBS, a spectral database containing high quality LIBS spectra on element components were constructed. Then, one-dimensional convolutional neural network (CNN) was introduced to distinguish five species of bismuth brass alloy. Amazingly, the optimal CNN model can provide an identification accuracy of 100 % for specie identification. To figure out the spectral features, we proposed a novel approach named “segmented fs-LA-SIBS wavelength”. The identification contribution from various wavelength intervals were extracted by optimal CNN model. It clearly showed that, the differences of spectra feature in the wavelength interval from 336.05 to 364.66 nm can produce the largest identification contribution for an identification accuracy of 100 %. More importantly, the feature differences in the four elements such as Ni, Cu, Sn, and Zn, were verified to mostly contribute to identification accuracy of 100 %. SignificanceTo the best of our knowledge, it is the first study on one-dimensional CNN configuration assisted with fs-LA-SIBS successfully employed for performing identification of bismuth brass. Compared with conventional machine learning methods, CNN has shown significant more superiority. To reveal the tiny spectra differences, the classification contribution from spectra features were accurately defined by our proposed “segmented fs-LA-SIBS wavelength” method. It can be expected that, CNN assisted with fs-LA-SIBS has great promising for identifying the differences from various element components in metallurgical field.

Heterogeneous amorphous/crystalline ZnZrCu biodegradable alloys with synergistic strength–plasticity prepared by mechanical alloying and laser powder bed fusion

ABSTRACT Amorphous Zn-based alloys have shown considerable potential for implant applications owing to the impressive strength. However, they inevitably fall into strength–plasticity trade-off dilemma due to shear bands softening. In this work, a novel and feasible route of mechanical alloying (MA) and laser powder bed fusion (LPBF) was first developed for manufacturing heterostructured ZnZrCu alloys. The results showed that MA destabilised atomic periodicity of Zn/Zr powders and induced amorphization. Furthermore, increasing Cu content enhanced amorphization ability and in-situ synthesised ϵ-phases, endowing ZnZrCu powders with heterostructure. During LPBF, the fast-melting kinetics and highly localised nature restricted devitrification and promoted the uniform distribution of ϵ-phases, constructing heterogeneous amorphous/crystalline ZnZrCu alloys. Consequently, ZnZrCu alloys exhibited good strength–plasticity synergy attributed to extra strain-hardening and hampering premature failure of shear bands. This study not only provides a feasible route to prepare biodegradable Zn-based alloys with strength–plasticity synergy but also sheds light on the design and manufacture of cutting-edge amorphous alloys.

Quantum Chemical Calculation on ScCl3-NaCl-KCl Molten Salt System

Background: The study of the ionic structure of the ScCl3-NaCl-KCl molten salt system is of guiding significance for the production of metal Sc and Sc alloy by molten salt electrolysis using ScCl3-NaCl-KCl molten salt system as electrolyte. However, limited research has been conducted on the structural analysis of molten salt within this system using Raman spectroscopy. Methods: The Gaussian and GaussView programs are used to simulate Sc-Cl ionic groups that may exist in the ScCl3-NaCl-KCl molten salt system based on density functional theory (DFT) and calculate their theoretical Raman spectra. Then, the wave function analysis of these Sc-Cl ionic groups is carried out using the Multiwfn program. Results: When the ScCl3-NaCl-KCl system is used as the electrolyte, it is considered that the 8 Sc atom in ScCl74− ionic groups is most easily reduced by electrochemistry at the cathode when the concentrations of eight Sc-Cl ionic groups are the same. In Sc2Cl7− Sc2Cl82− and Sc2Cl93− ionic groups, the sites that are most likely to attract electrophiles to attack and react are 1Cl and 7Cl, respectively, and the two Sc atoms located in the "chlorine bridge" structure contribute the most to LUMO orbitals, and nucleophiles will preferentially attack the Sc atoms located in the "chlorine bridge" structure. For Sc2Cl7−、Sc2Cl82− and Sc2Cl93− ionic groups, which have two Sc atoms, the bonds formed between Sc and Cl in the "chlorine bridge" structure have the smallest bond order, so the bonds formed by Sc and Cl in the "chlorine bridge" structure break first during the reaction, and then the bond formed by Sc and Cl located at both ends of the whole structure breaks Conclusion: The key information, such as bond length, point group structure, and theoretical Raman spectral characteristic peak after optimization, are obtained by the Gaussian and GaussView programs. The net atomic charge in each ionic group, the direction of electron migration during the formation of the ionic groups, the sites where electrophilic and nucleophilic reactions are most likely to occur in each ionic group, and the order of bond breaking during chemical reactions are obtained by the Multiwfn program.

Integrated manufacturing of powder metallurgy preparation-thixoforming for Al0.8Co0.5Cr1.5CuFeNi HEA: Excellent formability and enhancement by in-situ generated Al2O3 in liquid phase

Thixoforming displays wild application prospects in manufacturing Cu containing high entropy alloy (HEA) product. In current work, we proposed a novel manufacturing strategy on powder metallurgy preparation-thixoforming for Cu containing HEAs, integrating material preparation, shaping and strengthening objectives. During thixoforming, oxide in-situ generation in liquid phase was utilized to reinforce soft phase, achieving the strengthening of component. Based on this strategy, manufacturing of disc-shaped component for a model Al0.8Co0.5Cr1.5CuFeNi HEA was studied. Compared to 1175 °C thixoforming, room-temperature strength experiences a breakthrough increase at 1200 °C and 1225 °C, accompanied by an increase in yield strength of 323.8 MPa and 314.8 MPa, an increase in ultimate strength of 374.2 MPa and 470.0 MPa, meanwhile, fracture strain improves, which is caused by a considerable amount of in-suit generated Al2O3. Homogeneous and almost defect free microstructure obtained under higher temperature conditions ensures uniformity of mechanical properties for the whole component. As thixoforming temperature increases, preferred orientation of grain fiber shape becomes random, plastic deformation of solid grain (PDS) turns to flow of liquid incorporating solid particles (FLS), sliding between solid particles (SS) during material flow filling, which effectively reduces material damage risk caused by strain localization. In-situ generated Al2O3 in liquid phase helps to hinder crack propagation and blunt crack tip in Cu rich soft phase. Al2O3 only strengthens soft phase, relieving mismatch of strength-plasticity properties between soft and hard phase, accordingly, failure of soft phase is delayed and simultaneous improvement of strength and plasticity is achieved.

Jet on demand—A pneumatically driven molten metal jetting method for printing crack-free aluminum components

Additive manufacturing (AM) of many traditional aluminum alloys is difficult due to hot cracking during cooling, which motivates investigating alternative AM methods that can mitigate this challenge. Here we demonstrate a new pneumatically driven molten metal jetting (MMJ) AM technique which uses a longer pressure pulse width to produce a jet of liquid metal that reaches the heated build plate. The “jet on demand” technique is utilized to build Al-6061 parts on heated build plates. Due to the large thermal mass contained in each jet, excellent adhesion is observed between droplets and layers while still maintaining dimensional control to produce parts with high relative densities (>98%). While as-printed parts exhibit different microstructure and hardness than traditional Al-6061, both microstructure and hardness are restored to traditionally processed values through a traditional T6 heat treatment. Microhardness values of 104 HV were obtained for printed Al-6061, which compares well to wrought properties. We observe that high build plate temperatures allow for lower solidification rates and eliminate hot cracking. These results point to a method for additively manufacturing traditional aluminum or other alloys that cannot currently be additively manufactured due to hot cracking.

Manufacturing of heavy tungsten alloys from nano-sized metal oxides via simultaneous reduction-sintering powder treatments

Heavy tungsten alloys are of great importance in the engineering and mining industries as well as the military and medical applications because of their stability at high temperatures, high strength and dense structures. The present study develops a novel technology for the production of heavy tungsten alloys via thermal treatment of nano-sized metal oxides based on simultaneous reduction and sintering processes. Heavy tungsten alloy (95W-3Ni-2Fe) was produced from the reduction of mixed nano-sized metal oxides precursor in H2 at 1000 o C followed by sintering at 1350–1450 o C for 30–90 min. The reduced and sintered samples were characterized by XRD to follow up the crystallinity, total porosity measurement was used to find out the densification properties, the grain structure and morphology were examined by RLM and SEM attached with EDAX. Micro-hardness tester was also used to investigate the influence of sintering conditions on the grain densification. A fundamental study on the kinetics of reduction of mixed nano-sized metal oxides precursor was performed by isothermal and non-isothermal techniques. Both results from isothermal and non-isothermal tests were used to calculate the activation energy which was correlated with macro- and micro-structures to predict the corresponding reduction mechanism. However, the influence of sintering temperature and time on the crystallinity of the produced phases, grain structure, morphology, total porosity, pore-size distribution, bulk and apparent densities, and the hardness of sintered compacts was extensively investigated. The results revealed that the presence of NiO and/or Fe2O3 in the mixed metal oxides precursor was very important to ease the reducibility of WO3 as the metallic phases of Ni and/or Fe act as a catalyst for the reduction of WO3. The rate of reduction proceeds faster in the following order: NiO > Fe2O3 > mixed oxide > WO3. In non-isothermal experiments, it was found that the heating rate has a considerable effect on the reduction of precursor, i.e., the lower the heating rate, the higher the degree of reduction. It might be reported that the use of nano-sized metal oxides particles in the fabrication of heavy tungsten alloys greatly affects the main properties of the produced alloy. With the increase in sintering time, larger sizes of dense grains were developed, and the matrix became denser as a result of sintering and re-crystallization effects. The higher the sintering time, the higher the grain densification and the less pores formed in the matrix. On the other hand, with the increase in the sintering temperature, the grain boundaries were well defined in which the grains were composed of tungsten metal and surrounded by inter-metallics. The higher the temperature, the higher the XRD peak intensities of metallic tungsten and intermetallics as a result of sintering and re-crystallization.

Production of Neutron-Absorbing Zirconium-Boron Alloy by Self-Propagating High-Temperature Synthesis and Its Refining via Electron Beam Melting

Production of Neutron-Absorbing Zirconium-Boron Alloy by Self-Propagating High-Temperature Synthesis and Its Refining via Electron Beam Melting

Droplet transition behavior and compositional homogenization of TiAl alloys fabricated via dual-wire electron beam-directed energy deposition

The dual-wire electron beam-directed energy deposition (EB-DED) process presents considerable advantages for fabricating titanium aluminide (TiAl) alloys via in situ reactions between Ti and Al. However, variations in the thermophysical properties of pure Ti, pure Al, and TiAl alloys pose challenges in achieving consistent droplet transition behavior and uniform chemical composition. This study explored the effects of wire feeding modes on the forming quality of TiAl alloys and droplet transition behaviors and discussed compositional homogenization and elemental evaporation in TiAl alloy components. Both single-side and double-side feeding modes were utilized, and the electron beam directly melted the Ti wire in the double-side mode, thereby achieving superior surface morphology. Random disturbances and suboptimal wire feeding angles led to the wires deviating from the electron beam center and then being inserted into or passing through the molten pool, thereby degrading the forming quality. By positioning the Al wire tip beneath the Ti wire tip, a common droplet emerged as the Ti droplets melted the Al wire. The droplet transition behavior was regulated by the distance between the wire tips and component surfaces, achieving a liquid bridge transition at distances ranging from 0.75 to 5.82 mm. Although the droplet composition was generally uniform owing to elemental evaporation, the fluctuations among the droplets exceeded those observed in the as-deposited components. The extensive molten pool and keyhole effect enhanced compositional homogenization within the TiAl alloy components. During the deposition process, the evaporation rate of Al surpassed that of Ti due to its higher saturation vapor pressure, consequently yielding a lower actual Al content. The loss rate of Al initially decreased and then increased as the calculated Al content increased, which was influenced by the Al content in the molten pool and temperature variations. This research advances the fundamental understanding of TiAl alloy fabrication via in situ reactions and contributes to the development of the EB-DED process.

MATHEMATICAL MODELING OF THE NON-STATIONARY THERMAL STATE OF A COMPOSITE COATING OF CLOSE TO EQUIMOLAR COMPOSITION DURING LASER REMELTING

Based on assumptions and limitations, a mathematical model of the non-stationary thermal state of a composite coating during laser remelting on a metal substrate to obtain an alloy of equimolar or close to equimolar composition has been developed. The model includes the boundary value problem of calculating the nonstationary thermal state of the temperature distribution in the solid, two-phase and liquid regions, considering the heat release of crystallization according to the theory of a quasi-equilibrium two-phase zone in the presence of porosity of a mixture of metal powders. Based on the mathematical model, the computer program “Composite coating thermal state” was created, which allows to determine the non-stationary temperature distribution in the formed coating and substrate, the depth of penetration of the high-entropy coating layer, to evaluate the shrinkage of the molten coating under different technological conditions: laser power, the diameter of its focal spot, as well as the speed of movement along the surface of the processed material. The created program also allows to determine the dynamics of the position of two-dimensional liquidus and solidus lines for each metal included in the mixture. Using the created program, a computer simulation of the process of unsteady heating of a mixture of three metal powders in the same mass fractions: nickel, chromium and iron was carried out. Non-stationary temperature fields in the composite coating are obtained, considering its penetration and heating of the substrate. The depth of penetration of all metals, including the most low-melting one, was determined during laser remelting on a metal substrate in the production of a high-entropy alloy. The practical significance of the developed computer model lies in its use to predict the penetrationdepth of a composite coating under specified technological modes of laser remelting. At the same time, its adaptation is necessary, based on experimental data on the porosity and thickness of the coating before and after melting of simple metal systems with similar thermophysical properties.

Establishing a process route for additive manufacturing of NiCu-based Alloy 400: an alignment of gas atomization, laser powder bed fusion, and design of experiments

Alloy 400 is a corrosion-resistant, NiCu-based material which is used in numerous industrial applications, especially in marine environments and the high-temperature chemical industry. As conventional manufacturing limits geometrical complexity, additive manufacturing (AM) of the present alloy system promises great potential. For this purpose, a robust process chain, consisting of powder production via gas atomization and a design of experiment (DoE) approach for laser powder bed fusion (LPBF), was developed. With a narrow particle size distribution, powders were found to be spherical, flowable, consistent in chemical composition, and, hence, generally applicable to the LPBF process. Copper segregations at grain boundaries were clearly detected in powders. For printed parts instead, low-intensity micro-segregations at cell walls were discovered, being correlated with the iterative thermal stress applied to solidified melt-pool-near grains during layer-by-layer manufacturing. For the production of nearly defect-free LPBF structures, DoE suggested a single optimum parameter set instead of a broad energy density range. The latter key figure was found to be misleading in terms of part densities, making it an outdated tool in modern, software-based process parameter optimization. On the microscale, printed parts showed an orientation of melt pools along the build direction with a slight crystallographic [101] texture. Micro-dendritic structures were detected on the nanoscale being intersected by a high number of dislocations. Checked against hot-extruded reference material, the LPBF variant performed better in terms of strength while lacking in ductility, being attributed to a finer grain structure and residual porosity, respectively.