Solidification Of Melt Research Articles

Towards a theory of steady-state solidification process with a quasi-equilibrium two-phase region

AbstractThe process of directional crystallization in the presence of a quasi-equilibrium two-phase region located between the solid material and the liquid phase is studied theoretically. The mathematical model of the process is based on heat and mass transfer equations in the solid, liquid and two-phase regions, as well as boundary conditions at the phase interfaces “solid phase” – “two-phase region” and “two-phase region” – “liquid phase”, which are moving with a constant velocity. The process of directional crystallization is given by fixed temperature gradients in the solid and liquid phases, which determine a constant velocity of melt solidification. An exact analytical solution of the nonlinear problem with two moving boundaries of phase transformation is obtained, which is based on the transition to a new independent variable, the solid phase fraction, when integrating the nonlinear heat and mass transfer equations in the two-phase region. As a result of solving the problem, the distributions of temperature and concentration of dissolved impurity, the solid phase fraction in a two-phase region, the laws and velocities of motion of its interphase boundaries are determined. It is analytically shown that the impurity concentration and temperature in the two-phase region are only the functions of solid phase fraction, which, in turn, depends on the spatial coordinate. Analysis of the obtained solutions shows that the solid phase fraction in a two-phase region can be both a decreasing and increasing function of the spatial coordinate, which is directed from the solid material to the melt. This determines the internal structure of two-phase region, its permeability, average interdendritic spacing, distribution of dissolved impurity, crystallization velocity and laws of two-phase region boundaries.

A Phase-Field Model for Wet Snow Metamorphism.

The microstructure of snow determines its fundamental properties such as mechanical strength, reflectivity, or thermo-hydraulic properties. Snow undergoes continuous microstructural changes due to local gradients in temperature, humidity, or curvature, in a process known as snow metamorphism. In this work, we focus on wet snow metamorphism, which occurs when the temperature is close to the melting point and involves phase transitions among liquid water, water vapor, and solid ice. We propose a pore-scale phase-field model that simultaneously captures the three relevant phase change phenomena: sublimation (deposition), evaporation (condensation), and melting (solidification). The phase-field formulation allows one to track the temperature evolution among the three phases and the water vapor concentration in the air. Our three-phase model recovers the corresponding two-phase transition model when one phase is not present in the system. 2D simulations of the model unveil the impact of humidity and temperature on the dynamics of wet snow metamorphism at the pore scale. We also explore the role of liquid melt content in controlling the dynamics of snow metamorphism in contrast to the dry regime before percolation onsets. The model can be readily extended to incorporate two-phase flow and may be the basis for investigating other problems involving water phase transitions in a vapor-solid-liquid system, such as airplane icing or thermal spray coating.

Crystallization behavior of BOF slag during the cooling process towards leaching for CO2 sequestration

This work addresses the crystallization behavior and microstructure feature of the molten basic oxygen furnace (BOF) slag during a slow cooling process. The aim is to provide a reference for the modification of BOF slag for subsequent leaching of Ca as part of CO2 sequestration. Integrated analysis of XRD, SEM-EDS, and thermodynamic calculations suggest a crystallization behavior of BOF slag during the cooling process. RO phases ((Mg, Fe, Mn) O) was the equilibrium phase at a high temperature of around 1600 °C, followed at lower temperatures by the formation of Ca3SiO5 (C3S) and α-Ca2SiO4 (α-C2S). The Ca2Fe2O5 (C2F) phase forms during the latter stages of melt solidification. On the basis of the combined analysis of the leaching test results and crystallographic analysis, a future direction of modification of BOF slag is suggested that enriches Ca into the C2S and hinders the formation of C2F. However, inhibiting the generation of C2F by adjusting the cooling process alone is difficult since its crystallization rate is fast. The phase of C2F was observed in XRD and SEM even if the BOF slag was quenched from 1600 °C. Furthermore, the chemical characterization and morphological evolution of the crystalline phase of molten BOF slag during the slow cooling process was observed.

In Situ Observation of Precipitation Behavior of MnS during Solidification of Steel Melt Intended for Production of Nonquenched and Tempered Steel

Two heats of steel are melted using a vacuum induction furnace in the laboratory, with one heat undergoing magnesium treatment and the other being subjected to a combined magnesium–calcium treatment. The precipitation and agglomeration behaviors of inclusions of these two steel samples are observed using a high‐temperature confocal laser scanning microscopy. MnS precipitates form around oxide cores and undergo rapid growth during the solidification process of molten steel, and these MnS precipitates with oxide cores react with the cores, resulting in the transformation of the MnS into complex sulfides. In comparison with Al2O3 inclusions, MgO·Al2O3 inclusions have a lower critical velocity (V c), making them more susceptible to being engulfed by the solid–liquid interface. As the size of colliding inclusions increases, the coalescence–collision frequency (E 0) initially decreases until it reaches a minimum value. After that, with further size increments, the frequency starts to increase. During the inclusions growth process through collision, there is a distinct zone where coalescence–collision frequency is low. Inclusions that reach this zone struggle to grow further due to reduced collision coalescence, consequently leading to a predominance of inclusions with diameters in this zone.

Ultra-high volume expansion ratio branched PBT/TPEE three-dimensional reticulated foams of supercritical CO2 melt foaming for efficient oil/water separation

The development of polymer reticulated foams with high expansion ratios (VER) for selective oil-adsorption applications has been hindered by technical challenges. In this article, high VER reticulated foam with outstanding selective oil-adsorption performance was realized through the synergistic effect of molecular topological structure and blending heterostructure. Branched polybutylene terephthalate(B-PBT)/thermoplastic polyester elastomer(TPEE) was prepared by blending reaction. Then, B-PBT/TPEE blends were foamed by supercritical CO2 melting foaming, a solvent-free process. The nano-scale TPEE, acting as the weak point, induced the cell wall to rupture and form reticulated foam after the B-PBT had expanded to a high VER. The branching topological structure endowed PBT high storage modulus(G’) and complex viscosity(η*), which support the expansion of foam and keep foam from collapsing before the melt solidification. As a result, ultra-high VER three-dimensional reticulated foams possessing VER of 46.9 and open-cell content of 97.8 % were prepared, which is higher about 200 % than the previous research. The water contact angle of reticulated foams is 132° and cyclohexane droplets diffuse into reticulated foam showing the contact angle of 0°, indicating the reticulated foam have oleophilicity and hydrophobicity. The adsorption capacity of the reticulated foam for various oils is from 24 to 67 g/g. Moreover, the adsorption rate constant of reticulated foam is 8 times more than that of conventional open-cell foam. These benefits from the unique cell structure and high VER of reticulated foam. The work provides a facile and novel method for the green preparation of high-performance oil/water separation materials.

Variation in microstructural features of melt-pool structure in laser powder bed fused Al–Fe–Cu alloy at elevated temperatures

The present study was undertaken to understand the effect of annealing on the microstructural features of the melt-pool structure and the associated multiscale mechanical properties of the Al–2.5%Fe–2%Cu alloy manufactured by laser powder bed fusion (LPBF). Microstructural characterizations and tensile tests were conducted for the LPBF-built specimen and those subsequently annealed at various temperatures ranging from 200 to 500 °C. Nanoindentation hardness mapping was used to evaluate the mechanical inhomogeneity of the melt-pool structure and its changes by annealing at different temperatures. The LPBF-manufactured sample exhibited a melt-pool structure containing numerous particles of the Al23CuFe4 phase (oC28, orthorhombic structure) formed because of local melting and rapid solidification during the LPBF process. The relatively coarsened cellular structure localized along the melt-pool boundary resulted in local soft regions. The local vulnerability contributed to the direction dependence of the tensile ductility. A slight variation was observed in the inhomogeneous microstructure of the samples annealed at 200 or 300 °C. The formation of numerous Al23CuFe4 nanoprecipitates in the α-Al supersaturated solid solution prevented strength loss after post-heat treatments. In addition, considerable coarsening of the intermetallic phase after annealing at 500 °C eliminated the melt-pool structure. The tensile performance of the specimens demonstrated a ductile fracture mode, wherein ductile fracture occurred in the α-Al matrix with low hardness while the harder θ-Al13Fe4 stable phase was embedded within it. The anisotropy in the mechanical properties was less pronounced owing to the significant microstructural changes.

The temperature field characteristics and amorphous formation ability during the continuous casting process of Zr-based bulk metallic glass

This study utilized FLUENT dynamic mesh simulation technology to simulate the temperature field distribution characteristics during the continuous casting (CC) process of 5 mm thick Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 (Vit1) bulk metallic glass (BMG), analyzed and discussed the amorphous forming ability of the Vit1 BMG plate prepared through CC. The results indicate that during the CC process, the temperature gradient and cooling rate of Vit1 BMG plate decrease with increasing distance from the cooling copper block surface and prolonged solidification time. Even at the lowest cooling rate, it still remains significantly higher than the critical cooling rate (Rc) of Vit1 bulk amorphous alloy. The temperature variations recorded by the thermocouple during the alloy melt solidification process are in basic agreement with the simulation data. The experimental test and simulation results show that 5 mm thick Vit1 BMG slab can be prepared theoretically by continuous casting technology. Finally, XRD, DSC and TEM were used to analyze the amorphous formation ability and microstructure of the Vit1 BMG slab.

Strength and plasticity improvement induced by strong grain refinement after Zr alloying in selective laser-melted AlSiMg1.4 alloy

In order to enhance the mechanical properties of the selective laser-melted (SLM) high-Mg content AlSiMg1.4 alloy, the Zr element was introduced. The influence of Zr alloying on the processability, microstructure, and mechanical properties of the alloy was systematically investigated through performing microstructure analysis and tensile testing. It was demonstrated that the SLM-fabricated AlSiMg1.4−Zr alloy exhibited high process stability with a relative density of over 99.5% at various process parameters. Besides, the strong grain refinement induced by the primary Al3Zr particle during the melt solidification process simultaneously enhanced both the strength and plasticity of the alloy. The values for the yield strength, ultimate tensile strength, and elongation of the SLM-fabricated AlSiMg1.4−Zr were (343±3) MPa, (485±4) MPa, and (10.2±0.2)%, respectively, demonstrating good strength− plasticity synergy in comparison to the AlSiMg1.4 and other Al−Si-based alloys fabricated by SLM.

Thermal Performance Improvement of Composite Phase-Change Storage Material of Octanoic Acid–Tetradecanol by Modified Expanded Graphite

Phase-change cold storage technology is recommended as a solution for energy conservation and carbon neutrality in air conditioning systems of buildings. This study focuses on the development of binary composite phase-change materials comprising octanoic acid–tetradecanol (OA-TD). To enhance its thermal conductivity, expanded graphite (EG) was employed as an additive carrier, and the surface modification of EG particles using hexadecyltrimethoxysilane (HDTMOS) was attempted to make up for the instability and further to improve the performance of OA-TD/EG CPCMs. The OA-TD/EG-HDTMOS CPCMs were synthesized by EG mixed with EG-HDTMOS at a 1:1 mass ratio. The thermal performance and stability of the OA-TD/EG-HDTMOS CPCMs were thoroughly evaluated by multi-cycle melting–solidification and thermal conductivity measurements. The results revealed that the OA-TD mixture, when at a mass ratio of 77:23, exhibited a phase-transition temperature of 11.4 °C and a latent heat ranging from 150 to 155 J/g. Then, the OA-TD/EG-HDTMOS composite material, at a 12:1 mass ratio of OA-TD to EG-HDTMOS, solidified and melted at temperatures of 9.2 °C and 11.2 °C, with a latent heat ranging from 138 to 143 J/g, and significantly improved the thermal conductivity to 0.7 W/(m·K), representing a remarkable 133% increase compared to that of OA-TD alone. Even after undergoing 100 melting–solidification cycles, the OA-TD/EG-HDTMOS maintained superior phase-change thermal performance and stability, making it suitable for cold storage and energy conservation in air conditioning.

Influence of Mg Content on Microstructure Coarsening, Molten Pool Size, and Hardness of Laser Remelted Al(-x)-Mg-Sc Alloys.

Investigations leading to high-quality surfaces and optimized properties in laser remelted Al-Mg-Sc alloys remain scarce. Laser surface remelting (LSR) has been used for the final treatment of these alloys processed through additive manufacturing. However, the direct microstructure responses of the treated cast surfaces have not yet been investigated. In the present research, Al-3, 5, and 10 wt %-Mg-0.1 wt %-Sc alloys plates were processed using LSR to study the effects of local melting and rapid solidification. The morphology of the α-Al phase, microstructure coarsening, and hardness were mapped from the bottom to the top of the molten pools, varying with local Mg content and laser heat input (2.5 J/mm, 5 J/mm, and 10 J/mm). This study aimed to create a comprehensive map of the microstructures, hardness, and molten pool sizes under various conditions. The findings may help to optimize these alloys through understanding laser processing parameters. Methods used included CALPHAD computations, optical microscopy, SEM, EDS, image analysis, hardness tests, and heat flow models. The results obtained showed α-Al cell growth with bands in all alloys with hardness changes correlating with cell spacing and heat input. Higher Mg content resulted in more refined cells and a higher fraction of bands. Increased Mg content decreased the thermal diffusivity and enthalpy of melting, enlarging the molten pool size. Hardness increased with decreasing heat input and higher Mg content in the tested alloys, especially in the Al-10 wt %-Mg-0.1 wt %-Sc alloy as the heat input was varied.

Optimizing Selective Laser Melting of Inconel 625 Superalloy Through Statistical Analysis of Surface and Volumetric Defects

This article delves into optimizing and modeling the input parameters for the selective laser melting (SLM) process on Inconel 625. The primary aim is to investigate the microstructure within the interlayer regions post-process optimization. For this study, 100 layers with a thickness of 40 µm each were produced. Utilizing the design of experiments (DOE) methodology and employing the Response Surface Method (RSM), the SLM process was optimized. Input parameters such as laser power (LP) and hatch distance (HD) were considered, while changes in microhardness and roughness, Ra, were taken as the responses. Sample microstructure and surface alterations were assessed via scanning electron microscopy (SEM) analysis to ascertain how many defects and properties of Inconel 625 can be controlled using DOE. Porosity and lack of fusion, which were due to rapid post-powder melting solidification, prompted detailed analysis of the flaws both on the surfaces of and in terms of the internal aspects of the samples. An understanding of the formation of these imperfections can help refine the process for enhanced integrity and performance of Inconel 625 printed material. Even slight directional changes in the columnar dendrite structures are discernible within the layers. The microstructural characteristics observed in these samples are directly related to the parameters of the SLM process. In this study, the bulk samples achieved a microhardness of 452 HV, with the minimum surface roughness recorded at 9.9 µm. The objective of this research was to use the Response Surface Method (RSM) to optimize the parameters to result in the minimum surface roughness and maximum microhardness of the samples.

Process exploration for scale melting and solidifying of municipal solid waste incineration (MSWI) fly ash by horizontal cyclone melting furnace

This study used the horizontal tubular heating furnace to explore the melting potential of circulating fluidized bed (CFB) incinerator fly ash and mechanical grate furnace (MGF) incinerator fly ash. The horizontal cyclone melting furnace was then built to explore further the feasibility of scale melting of MSWI fly ash. The melting characteristic temperature, amorphous content, and heavy metal leaching concentration characterized the melting potential and solidification effect of MSWI fly ash. The experimental results show that the amorphous content of CFB fly ash after melting is up to 92.37%, and the volatilization rate of heavy metals Zn, Pb, and Ni does not exceed 30%. MGF fly ash exhibits the “sintering into shells” phenomenon during heating, and the leaching concentrations of heavy metals Pb in the sintered products still exceed the standard limits. In addition, the volatilization rates of heavy metals Cu, Zn, Cd, Pb, Cr, and Ni in Slag II are above 50%, and the volatilization rate of Cr reaches 85%. So, slag’s amorphous content also affects heavy metals’ volatilization rate. The MSWI fly ash melting characteristic temperature decreases with the decrease of alkalinity value. When the alkalinity value drops to 0.6, the melting characteristic temperature reaches its lowest value. Mixing 80% CFB fly ash or 50% MGF bottom ash into MGF fly ash can significantly enhance the melting potential to reduce hazardous waste. When using the horizontal cyclone melting furnace to process MSWI fly ash on a large scale, MSWI fly ash achieves an excellent melting effect with an amorphous content of over 93% at the positions of the furnace middle section, inner tail cone, slag discharge outlet, and flue gas outlet. The fly ash particles are in motion in the melting furnace, so the particle size distribution affects the melting effect of MSWI fly ash.

Application of Numerical Modeling and Finite Element Analysis in Fused Filament Fabrication: A Review.

Additive manufacturing (AM) is not necessarily a new process but an advanced method for manufacturing complex three-dimensional (3D) parts. Among the several advantages of AM are the affordable cost, capability of building objects with complex structures for small-batch production, and raw material versatility. There are several sub-categories of AM, among which is fused filament fabrication (FFF), also commonly known as fused deposition modeling (FDM). FFF has been one of the most widely used additive manufacturing techniques due to its cost-efficiency, simplicity, and widespread availability. The FFF process is mainly used to create 3D parts made of thermoplastic polymers, and complex physical phenomena such as melt flow, heat transfer, solidification, crystallization, etc. are involved in the FFF process. Different techniques have been developed and employed to analyze these phenomena, including experimental, analytical, numerical, and finite element analysis (FEA). This study specifically aims to provide a comprehensive review of the developed numerical models and simulation tools used to analyze melt flow behavior, heat transfer, crystallization and solidification kinetics, structural analysis, and the material characterization of polymeric components in the FFF process. The strengths and weaknesses of these numerical models are discussed, simplifications and assumptions are highlighted, and an outlook on future work in the numerical modeling and FE simulation of FFF is provided.

High-speed synchrotron X-ray imaging of melt pool dynamics during ultrasonic melt processing of Al6061

Ultrasonic processing of solidifying metals in additive manufacturing can provide grain refinement and advantageous mechanical properties. However, the specific physical mechanisms of microstructural refinement relevant to laser-based additive manufacturing have not been directly observed because of sub-millimeter length scales and rapid solidification rates associated with melt pools. Here, high-speed synchrotron X-ray imaging is used to observe the effect of ultrasonic vibration directly on melt pool dynamics and solidification of Al6061 alloy. The high temporal and spatial resolution enabled direct observation of cavitation effects driven by a 20.2 kHz ultrasonic source. We utilized multiphysics simulations to validate the postulated connection between ultrasonic treatment and solidification. The X-ray results show a decrease in melt pool and keyhole depth fluctuations during melting and promotion of pore migration toward the melt pool surface with applied sonication. Additionally, the simulation results reveal increased localized melt pool flow velocity, cooling rates, and thermal gradients with applied sonication. This work shows how ultrasonic treatment can impact melt pools and its potential for improving part quality.

Inhomogeneous deformation in melt-pool structure of Al-Fe-Cu alloy manufactured by laser powder bed fusion

Abstract The laser powder bed fusion (L-PBF) processed Al–2.5Fe–2Cu (mass%) alloy exhibited a high tensile strength above 340 MPa and pronounced directional dependence. The sample exhibited a characteristic inhomogeneous microstructure (in melt-pool structure) arising from the local melting and rapid solidification in the L-PBF process. The coarsened cellular structure localized along the melt pool boundary resulted in the local soft regions affected by the melt pool structure. The local vulnerability contributed to the direction dependence of the tensile ductility of the specimen.

An exploratory study on miniaturized additive friction stir deposition

Without melting and rapid solidification, additive friction stir deposition offers a deformation processing route to additive manufacturing and repair of high-performance alloys with full density and desirable properties. However, this approach has traditionally relied on expensive and bulky equipment, posing challenges for small-feature creation and portability. Here, we explore miniaturized additive friction stir deposition by modifying an affordable benchtop mill and introducing innovative tool design. With in situ monitoring of temperature and force evolution, we demonstrate the efficacy of this approach by dissimilar metal printing, depositing high-strength martensite steel (AISI 4140) onto mild steel (AISI 1018). Compared to conventional facilities, the present approach reduces the in-plane dimension of the feed-rod by a factor of three and narrows the deposition tracks to a few millimeters in width. The as-deposited steel exhibits full density and retains martensitic characteristics without forming new phases at the interfacial region. The as-deposited steel shows significant microstructure refinement with increased hardness because of the extreme thermomechanical conditions during deposition. We discuss the influences of downsizing on the thermal and mechanical aspects of deposition. Owing to the size effects in heat generation and heat loss, the rotation rate of the print head needs to be significantly increased in miniaturized additive friction stir deposition to ensure good deposition quality. To prevent buckling, the unsupported length of the feed-rod should be reduced in proportion to its in-plane dimension.

Atomic sawtooth-like metal films for vdW-layered single-crystal growth

Atomic sawtooth surfaces have emerged as a versatile platform for growth of single-crystal van der Waals layered materials. However, the mechanism governing the formation of single-crystal atomic sawtooth metal (copper or gold) films on hard substrates (tungsten or molybdenum) remains a puzzle. In this study, we aim to elucidate the formation mechanism of atomic sawtooth metal films during melting–solidification process. Utilizing molecular dynamics, we unveil that the solidification of the liquid copper initiates at a high-index tungsten facet with higher interfacial energy. Subsequent tungsten facets follow energetically favourable pathways of forming single-crystal atomic sawtooth copper film during the solidification process near melting temperature. Formation of atomic sawtooth copper film is guaranteed with a film thickness exceeding the grain size of polycrystalline tungsten substrate. We further demonstrate the successful growth of centimeter-scale single-crystal monolayer hexagonal boron nitride films on atomic sawtooth copper films and explore their potential as efficient oxygen barrier.

Защита деталей горного оборудования, работающих в условиях подземных выработок от биокоррозии

Introduction. Biological corrosion of mining equipment parts is an important problem. Ti-Cu-based coatings provide effective protection against such corrosion. A significant number of mining equipment parts operate under conditions of intense wear. These are parts such as pins, rollers, gears, racks, drive stars, etc. When applying a coating to such parts, it is important not only to increase the anti-corrosion properties, but also to maintain or improve the tribological properties of the parts being processed. The use of coatings based on metal oxides is an effective tool to combat bio corrosion. Among such metal oxides, nanocomposites that include a combination of TiO2 and Cu2O have performed best. These composites have a narrow bandgap, chemical stability and low toxicity. However, the issue of their influence on the tribological properties of parts remains incompletely studied. The purpose of this work is to analyze the structural features, mechanical properties and wear resistance of the Ti-TiO2-Cu-Cu2O coating applied by detonation spraying. Materials and methods. In this work, Ti-TiO2-Cu-Cu2O composite coatings were formed on a steel substrate. Sputtering was carried out using a multi-chamber detonation accelerator system. The coating process was carried out layer by layer using a device that moved back and forth with a lateral displacement. Titanium (PTN-8VT10) and copper (PMS-1) powders were used as raw materials. Wear tests were carried out using a disk-pin design. X-ray structural analysis was carried out for the obtained samples, and the microstructure of the coatings was studied. The micro hardness of the applied coating was also determined. Results. In the resulting coatings between the two elements Ti and Cu of the deposited powders, no chemical reaction or intermetallic compounds were detected. Ti-TiO2-Cu-Cu2O composite coatings mainly consisted of TiO2 and Cu2O, with titanium and copper acting as a binder, providing a high density of the composite material. Distinct formations of metallic Ti and Cu particles are observed in various regions of the microstructure, with many formations of metallic Ti retaining their spherical shape. The Ti-TiO2-Cu-Cu2O coating has a high average hardness of 640 HV0.2. The coefficient of friction when the Al2O3 counter body slides over the coating after a short running-in cycle did not change and amounted to 0.38. Discussion. The analysis of the cross section revealed that the coating material has a dense structure, characterized by strong inter lamellar-type connections, and has no signs of destruction or cracks. The absence of cracks and delamination along the boundary between the substrate and the coating indicates the high quality of adhesion to the base. The thickness of this composite coating is approximately 340 ± 20 micrometers. The increased hardness of this coating can be explained by the partial melting and rapid solidification of powder particles during spraying, as well as its lamella-type compositional structure. The micro hardness profile inside the Ti-TiO2-Cu-Cu2O coating remains uniform. During tribo-technical tests with a 100Cr6 counter body, the friction coefficient of the tribo couple after running-in decreased as the sliding cycles increased. This effect is due to the formation of a tribo layer on the worn surface of the coating, which serves as protection against severe wear. These conditions prevent the counter body from sticking to the coating surface, which reduces the likelihood of adhesive wear. The main composition of the sealing tribo layer is iron oxide, formed as a result of an increase in temperature on the sliding surface and wear of the steel counter body during dry sliding, which prevents adhesion in contact. Conclusions. The authors conclude that during the spraying of a Ti-Cu powder mixture, ceramic reinforcement is formed, where titanium and copper, interacting with atmospheric components at the time of spraying, are capable of forming new oxide phases. Due to the absorption of oxygen by titanium and copper during the deposition process, the resulting composite acquires an average micro hardness of 640 HV0.2. The analysis of the cross-section of the coating revealed that the coating has a thickness of about 300 microns, has a dense structure characterized by strong interlamellar-type connections, and has no signs of destruction or cracks. Resume. The results obtained show that Ti-TiO2-Cu-Cu2O coatings applied to critical parts of mining equipment not only protect them from bio-corrosion, but also increase tribological properties. This allows you to increase the maintenance-free service life of equipment in mining operations. Suggestions for practical applications and future research directions. Ti-Cu composite coatings obtained by detonation thermal spraying can be used for such parts of mining equipment as pins, rollers, gears, racks, drive stars, etc. These coatings can be used not only to protect mechanisms and structural elements in mining conditions, but also for equipment elements operating in humid climates.

Effect of Mn content in the Ti/Zr-based AB2 Laves type alloys on their electrochemical performance

In this work, we studied the impact of Manganese content on the structural and electrochemical properties of the AB2 Laves phase alloys. These multicomponent alloys were composed of 7 individual constituents with a composition Ti0.15Zr0.85La0.03V0.12Mn0.7+xFe0.12Ni1.2 and a variable Manganese content, x = 0.021, 0.035, 0.070. The alloys were prepared using arc melting and rapid solidification techniques. These alloys were characterized by X-ray diffraction and Scanning Electron Microscopy with X-ray Energy Dispersive Spectroscopy allowing to probe the phase-structural composition of the alloys, their microstructures, and elemental distribution among the phase constituents. The rapidly solidified alloys exhibited refined microstructures with a more uniform elemental distribution compared to their as-cast counterparts, the latter containing larger grain sizes and clustered La-rich phases. C15 and C14 Laves type structures contributed to the phase-structural composition of the alloys, with their proportions influenced by the Manganese content and the chosen preparation method. The study revealed a multi-feature relationship between the Manganese content, the phase abundances, and the electrochemical performances, with notable disparities between as-cast and rapidly solidified alloys. The alloy containing 3 wt% Manganese demonstrated the highest discharge capacity and superior activation performance for both preparation methods, suggesting the best choice when optimizing the composition of the anodes for achieving the best battery performance. The highest hydrogen diffusion rate was observed for the alloy containing 10 wt% Manganese which can be related to the catalytic role of Manganese in the processes of hydrogen exchange when present in these alloys.

Numerical study on migration and solidification behavior of molten droplets on structure surface and in debris voids during debris bed melting process

The melt migration and solidification behavior on the surface of metal structure and in the debris voids is a key phenomenon of debris bed melting, which has an important impact on the assessment of reactor pressure vessel damage and melt leakage. In this study, the moving particle semi-implicit (MPS) method with high-order discretization scheme was coupled with a surface tension model that was established based on interface reconstruction. The migration and solidification behavior of UO2–ZrO2 and Fe–Zr melts on the metal structure surface and in the debris voids were investigated with the improved MPS method. The effects of temperature, velocity, contact angle and droplet diameter on the melt migration and solidification were analyzed. The results showed that the molten UO2–ZrO2 droplet on the metal structure surface presented three stages with solidification rate decreasing, while the solidification rate of molten Fe–Zr droplet had little change. The maximum spread factor and solidification rate increased with the increase of droplet falling velocity, but the spread factor was independent of the melt type at the same velocity. The high-temperature molten droplet penetrated the voids formed by the debris with diameter of 5 mm more easily compared to the voids formed by the debris with diameter of 3 mm. The influence of contact angle on the migration of molten droplet with initial velocity was small, and the maximum difference in droplet mass fraction was about 6%. Three groups of molten droplets with different diameters penetrated the voids, and the average increments of penetration mass fraction were 2.3%, 2.7% and 5.8%, respectively, with the increase of velocity. Near the bottom of the debris bed, the molten droplet without initial velocity solidified and blocked the flow channel, but the molten droplet with initial velocity of 0.5 m/s penetrated through the debris voids. The droplet with initial velocity of 0.5 m/s had a faster solidification rate in the voids compared to the droplet without initial velocity, and the droplet solidification mass fraction was 96.27% when the initial melt temperature was 1410 K.