Annotation of the results obtained in 2022
During the implementation of project No. 19-79-30025 "Development of scientific and technological basis for the design of aluminum-matrix composites and their production by additive laser methods for industrial application", a wide range of scientific research was carried out in accordance with the stated plan, and the results obtained during the implementation were summarized. On the basis of experimental experience, generalized methods, route maps and models have been developed, and recommendations have been formulated for using the results obtained in practice and introducing the developed materials and technologies in industry. The main results of the project in 2022 are presented below: - It has been shown that the modification of AlSi10Mg powder using both graphene and ZrN makes a significant contribution to the strengthening of the material and improves the mechanical properties of the samples after synthesis. The highest value of tensile strength, as in the case of hardness, is achieved when modified using 15% ZrN; the tensile strength of such a material reaches 475 MPa. However, in this case, the values of relative elongation noticeably decrease. The highest plasticity is achieved by modifying the silumin powder with 1.5% graphene particles. The drop in plasticity values for the material with the addition of ZrN is associated with additional hardening by the Petch-Hall mechanism. As can be seen from the analysis of the results of optical microscopy, there are practically no elongated large grains in the microstructure, which leads to additional hardening. Since strength and ductility are competing properties, with an increase in strength, a decrease in the relative elongation of the material is observed. - By conducting experiments on the recycling of powders remaining in the chamber after printing, and analyzing the unused powder from the printing zone, it was shown that such a powder can be used for the next 3D printing cycles while maintaining its morphology and did not significantly affect the final properties of the synthesized products. The main recommendation in this case is the need to screen such powders to screen out large agglomerates of particles that arise as a result of sparking during laser synthesis. Two main powder recycling strategies have been proposed: a one-volume powder strategy (reuse of unmelted powder after sieving) and a mixing strategy with the original powder, in which the used powder is periodically mixed with the original. - A generalized route map of the technology for the synthesis of products from various aluminum matrix composite materials was developed, consisting of three fundamental stages, the sequential implementation of which allows achieving the optimal mechanical properties of the synthesized material / product: preparation and control of the initial powder material, the procedure for 3D printing of test samples and 3D printing of the final product. The requirements and conditions for the implementation of the developed route map are formulated, including requirements for starting materials, a description of the necessary equipment and synthesis by the method of selective laser melting. - A technology for the production of products with a complex periodic structure by selective laser melting was studied using the example of an aluminum matrix composite AlSi10Mg + ZrN. Ordered porous structures based on bcc, fcc, and gyroid cells were chosen. Porous samples based on different unit cells had a porosity in the range of 49–86%. When examining the samples using microcomputed tomography, no zones with insufficient powder fusion were found, the relative density of the samples was 99.96%, and it was also demonstrated that the main number of deviations from the geometry is concentrated on the overhanging surfaces. It is shown that the yield strength and Young's modulus for ordered structures have a linear dependence on porosity, and the choice of the bcc, fcc, or gyroid unit cell does not have a strong effect on the mechanical properties in the selected macroparameter window. - Taking into account the array of experimental data formed during the implementation of the project, a generalized statistical model was presented for predicting the properties of products obtained by selective laser melting, depending on the synthesis modes. The model is based on the response surface method with experiment planning. Using this approach, it is possible to reduce the number of samples required to analyze the influence of each technological parameter. The relative density of the samples, measured by metallographic analysis, was used as the response variable. The main parameters of the process were continuous factors: laser power, scanning speed, overlap parameter, and layer thickness. Using correlation analysis, the influence of each process parameter on the formation of defects due to insufficient fusion or metallurgical porosity was determined. It was concluded that scanning speed is the most influential factor in terms of the formation of different types of pores. Using the model, a technological map was built in the P–V coordinates for the AlSi10Mg aluminum matrix. This flow chart was tested on experimental data obtained earlier in the course of the project. - Studies carried out within the framework of this project and aimed at forming a knowledge base on the creation of aluminum matrix composite materials by selective laser melting, allow us to conclude that this class of materials has a unique set of mechanical and functional properties, which makes them promising for further development and implementation, taking into account and the economic efficiency of the proposed materials and approaches. Based on the developed generalized route map, a number of recommendations were formulated for its use in industry, including regarding the choice of composition and type of aluminum matrix composite material and the choice of a strengthening additive (nano- or micro-sized particle distribution). - A school for young scientists "Additive Technologies - Science and Production 2022" was successfully held, which was held online. Leading scientists and industry representatives working in the field of additive technologies spoke at the school. More than 180 participants were registered at the event, of which 138 are students, graduate students and Russian young scientists under the age of 35 from various universities and scientific organizations. - The total number of publications on the project in journals indexed by Scopus / Web of Science in 2019-2022 reached 48 with the planned indicator of 42 papers, which is an overfulfillment of the stated plan. - The results of this project were presented at 4 scientific conferences and events. Thus, all the tasks set within the framework of the project for 2022 were completed in full with the achievement of all expected results.

 

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Annotation of the results obtained in 2019
The first stage of the scientific project "Development of scientific and technological bases of design of aluminum matrix composites and their production by additive laser methods for industrial application" was carried out. Analytical review of modern scientific and technical literature on the subject of the project was carried out. The properties of the most common aluminum powders for additive manufacturing have been studied. The compositions of aluminum matrix composites are considered. Ways to obtain them are studied. The directions of further researches are defined. Laboratory stands for obtaining aluminum matrix composites have been developed and manufactured: - laboratory stand for electrochemical oxidation of aluminum powder; - laboratory stand for hydrothermal oxidation of aluminum powder; - laboratory stand for production of AlN and AlON precursors for aluminum matrix composites by self-propagating high-temperature synthesis; - laboratory stand for mechanical mixing of aluminum matrix and reinforcement; - laboratory stand for obtaining aluminum powder from its castings. The parameters for obtaining Al-Al2O3 and Al-AlN/AlON powder composites are established. The detailed characteristic of the received composite materials is carried out. Some aspects of formation of structure and properties of aluminum matrix composites are considered. Thermodynamic calculations of aluminum alloys are carried out. The method for determining the suitability of aluminum powders for additive manufacturing is proposed. Experimental studies of 3D objects synthesis by selective laser melting were carried out using the obtained composite materials. The study of synthesized 3D objects was carried out: the microstructure of objects was studied, the level of mechanical characteristics was assessed. Optimal parameters of selective laser melting of Al–10 wt.% Al2O3 powder composite were determined using mathematical modeling methods. Methods of synthesis of various 3D objects by selective laser melting have been worked out. Published 8 articles in leading journals Scopus and Web of Science. All-Russian (with international participation) conference and school for young scientists "Additive technologies in digital manufacturing. Metals, alloys, composites" was successfully carried out. Materials of the school-conference are available on the website: http://3d.misis.ru/

 

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Annotation of the results obtained in 2020
The second stage of the project "Development of scientific and technological basis for the design of aluminum-matrix composites and their production by additive laser methods for industrial application " was completed. In 2020 the following works and studies were carried within the framework of the project: – selective laser melting parameters of aluminum-matrix composites containing ceramic and carbon additives (graphene, diamond, and carbon nanofibers) were studied, including the characteristics of composite materials; the influence of the selective laser melting parameters on the characteristics of the produced samples; the mechanical properties of synthesized 3D objects; –- the production methods for the compositions "aluminum oxide – nanodiamond" and "aluminum oxide – carbon nanofibers", intended for the reinforcement of aluminum matrix composites, were proposed and developed; – technologies for aluminum powder coating by the nanodiamond and multigraphene were proposed and tested; – a new aluminum alloy based on the Al-Ca-Ni-Mn system was developed and its features as initial material for selective laser melting were considered; – models describing the relationship between the parameters of selective laser melting and the mechanical properties of synthesized objects were developed using statistical data processing. During the project implementation in 2020, 10 publications were prepared in Sсopus / Web of Science journals. 5 of them were in the first quartile journal (Q1) according to the SJR classification (Scientific Journal Rankings, scimagojr.com). Online school "Additive technologies of the future: Materials, Methods and Prospects" for young scientists and students was held. More than three hundred participants were registered on the official website of the event, and later they were joined by more than a thousand online listeners. According to the registration data, the geography of the event included almost all subjects of the Russian Federation, as well as major cities from Kaliningrad to Vladivostok. Official website of the online school: http://3d.misis.ru/additive_school Full online school record: https://youtu.be/LhvwNfOqwnY NUST MISIS press releases reflecting the results and progress of the project: – "New technology for the production of high-strength aluminum composites for the aerospace industry": https://misis.ru/university/news/science/2020-06/6669/ – "NUST MISIS improves 3D printing technology for aerospace composites using oil production waste": https://misis.ru/university/news/science/2020-11/7076/ – "NUST MISIS held the second school on additive technologies of the future": https://misis.ru/university/news/science/2020-10/6979/

 

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Annotation of the results obtained in 2021
A wide range of scientific studies was carried out within the framework of the project No. 19-79-30025 " Development of scientific and technological basis for the design of aluminum-matrix composites and their production by additive laser methods for industrial application" (supervised by Professor, Dr. hab. A.A. Gromov) implementation in 2021. The main results are presented below. - A unified method for determining the regimes of 3D samples synthesis and their testing was developed. The proposed method consists of the following operations. 1) Control of the powder fluidity and the average particle size to determine the optimal thickness of the powder layer (t); 2) Selection of the distance between adjacent vectors (h) based on the results of single tracks study; 3) Selection of optimal parameters of laser power (P), laser scanning speed (V), and technological window of optimal regimes (EDv) based on the results of synthesis and analysis of porosity of cubic samples with a 5x5 mm cross-section; 4) Determination of synthesized samples hardness according to the optimal regimes by the Vickers method; 5) Determination of mechanical characteristics using uniaxial tensile tests of microsamples synthesized by optimal regimes. When compiling the methodology, the possibilities and expediency of testing microsamples for tensile tests (with a working length of 5.0 mm and a cross-section of 1.45 × 0.65 mm using special adapters) were shown to save the initial powder material. The developed author's technique was tested on ten powder compositions and demonstrated a high convergence of the obtained values. - Compositions AlSi10Mg – WC (wt. 0.5%, 1%, 5%, 10%, 15%) were prepared by mixing in a planetary ball mill. A study of the prepared powder compositions characteristics was carried out by the developed method. For each composition, main characteristics were determined, including the morphology of the powders, their flowability, bulk density, and the chemical and phase compositions. The results showed the applicability of the prepared compositions for further synthesis by the SLM method. - The technological foundations of silumin powder materials obtained by spraying were developed. An Atolab atomizer was used to obtain the initial powder material. With a sonotrode in the spraying process, it was possible to produce spherical metal powders. Due to the ordered nature of the oscillation process after spraying, the resulting powder had a very narrow particle size distribution. The morphology of the powder obtained by the described method and subsequent sieving through sieves with a mesh size of 60 μm met the requirements for powders for SLM with a spherical shape, high flowability of the particles, and bulk density. - 14 variants of powder compositions with different concentrations of strengthening additives were obtained and prepared for synthesis by the SLM method: variants modified by micron-sized particles ((AlSi10Mg – AlN (1%, 5%, 10%), AlSi10Mg – ZrN (1%, 5% , 10%)) and variants modified by carbon-containing nanoparticles (AlSi10Mg – Graphene (0.5%), AlSi10Mg – Nanodiamond (0.1%; 0.25%; 0.5%), AlSi10Mg - CNF (0.5% , 1%, 1.5%, 2%). The selection of the optimal synthesis parameters for these compositions made it possible to develop the following criteria for selecting promising compositions for additive technologies: 1) The procedure for mixing composite powders should ensure a uniform distribution of components. 2) A powder composite material's physical and technological parameters (flowability and particle size distribution) must meet the requirements of the SLM process. 3) Particles of the modifying additive should have high thermal stability, remain in the structure after synthesis, and ensure homogeneous distribution during synthesis according to optimal parameters. 4) Modifying particles should have high wettability with the matrix melt and retain in the structure after crystallization. 5) The morphology of the particles should preferably be spherical and retain geometry after the SLM process to provide the hardening effect. 6) The physical properties (hardness and elastic modulus) of modifying particles must significantly exceed the characteristics of the matrix, providing the hardening effect. 7) The modifying particle concentration during the optimal parameters window should ensure no more than 1% residual porosity. - Investigations of the mechanical characteristics of 3D products obtained by selective laser melting of various compositional compositions were carried out. The maximum hardness of 191 ± 13 HV was achieved by modification with WC particles in an amount of 15 wt.%, which is 65% higher than the hardness of the initial AlSi10Mg material (116 HV). A 53% decrease in wear was observed for 15 wt.% WC composite compared to the matrix. The addition of 10 wt.% ZrN resulted in a 30% reduction in wear. The highest hardness of 172 HV was observed for samples with 1.5 wt.% CNF, while adding 0.5 wt.% of graphene, allowed a hardness of 166 HV. The maximum uniaxial tensile strength of 432 MPa was obtained by adding 1.5 wt.% CNF corresponds to a 23% increase in strength compared to the initial AlSi10Mg alloy. The strength of the material increases with an increase in the WC concentration and reaches the maximum values of the ultimate strength of 410 MPa at a concentration of 15 wt.%, while the values of the relative elongation decrease to 2.8%. - The peculiarities of synthesis regimes for micro- and bulk samples of aluminum-matrix composites were studied. It was found that the smallest wall thickness that can be achieved using aluminum-matrix composites is about 150 μm, which is the limit of the resolution of the SLM technology for such materials. In this case, for micro-objects, a regime with a higher energy input was selected compared to the internal shading of massive objects. A method of the optimal regimes of micro-objects printing was presented, consisting of thin walls printing with different angles between the sample and the substrate surface. - The possibility of drum-type electrostatic separators used for fractionation of silumin powders for 3D printing was investigated. The studies were carried out on ASP-30 aluminum powder. The optimal characteristics of the fractionation process were determined. It was shown that the powders had a narrower particle size distribution after fractionation. This demonstrates the possibility of using drum-type electrostatic separators for powders fractionation. In addition, in 2021, within the framework of the project, 14 scientific articles were published in leading international journals indexed by Scopus / WoS, 4 of which belong to the first quartile Q1 according to SJR. Also, on July 23, 2021, a School for students and young scientists was held, which was performed within the framework of the International Aviation and Space Salon MAKS 2021. 14 leading scientist-lecturers from Russia, Germany, Switzerland, and 71 listeners, including 51 young Russian scientists, graduate students, and students up to 35 years old, took part in the summer school work. Link to the video of the School's broadcast: https://www.youtube.com/watch?v=3WZSRZ6vyVU

 

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