Melting Parameters Research Articles

Speed function effects on properties of Ti-5Al-5Mo-5 V-1Cr-1Fe alloy manufactured by electron beam melting

The speed function (SF) parameter, which is a unique combination of beam speed and beam current, is one of the most important parameters of the electron beam melting (PBF-EB) production process. It allows the same process conditions (size of the melt pool, process temperature, etc.) to be maintained for parts with different geometries and sizes. The aim of this research was to understand the effect of SF on the Ti-5Al-5Mo-5V-1Cr-1Fe alloy produced by electron beam melting technology. The results showed that increasing the SF from 86 to 116 resulted in a decrease in the average process temperature, a decrease in the length of the α phase plates, and change in the proportion of α and β phases from 53% (SF 86) to 50% (SF 116) of the β phases. Differences in microstructure (column diameters, thickness, and length of α-phase plates), phase composition, microhardness, porosity at the bottom, and top of the samples were observed on all samples. The mechanical property analysis did not show a significant effect of SF on elongation, but an increase in SF from 86 to 96 resulted in an increase in ultimate tensile strength (UTS) of approximately 7%, whilst an additional increase to 116 resulted in a decrease in UTS of approximately 8.5% compared to SF 96. From the results, it can be seen that the microstructural and mechanical properties of the material strongly depend on the SF. Based on it, SF 86 can be considered as the recommended value for the manufacture of Ti-55511 alloy parts.

Effect of Technological Parameters of Selective Electron Beam Melting on Chemical Composition, Microstructure, and Porosity of a TiAl-Alloy of Ti-Al-V-Nb-Cr-Gd System

Effect of Technological Parameters of Selective Electron Beam Melting on Chemical Composition, Microstructure, and Porosity of a TiAl-Alloy of Ti-Al-V-Nb-Cr-Gd System

The relationships between enthalpy and volume changes of aromatic compounds on melting at Tm and 298.15 K

Establishing the relationship between the thermodynamic parameters of melting, on the one hand, and the structural and physicochemical parameters of molecular compounds, on the other, is a long-standing problem. The volume change on melting has been long thought to be related to the entropy of fusion. In this work, we attempted to reveal the connection between the volume change on melting and the thermodynamic parameters of fusion of non-hydrogen-bonded aromatic compounds. Comparative analysis of the fusion enthalpies of different compounds, inherently melting under different conditions, may be ambiguous. Therefore, we additionally employed our recent findings on the experimental determination of the temperature dependence of the fusion enthalpy to adjust the quantities to the same temperature, 298.15 K. Linear correlations were established both at Tm and 298.15 K. An opportunity to use the correlation established at 298.15 K for predicting the fusion and sublimation enthalpies from the crystal density at 298.15 K and the molecular structure, taking advantage of existing approaches for predicting the molar volume of liquids and vaporization enthalpies, was demonstrated. Further investigation of these relationships might help to understand the nature of the melting process.

Investigation and validation of the flow stress equation and damage model parameters of an electron beam melted Ti6Al4V alloy with a martensitic phase

The Johnson and Cook flow stress and damage model parameters of an electron beam melt (EBM)-Ti64 alloy composed of α' (martensite) and α+β and an extruded-annealed conventional Ti64 alloy were determined experimentally. The validities of the determined flow stress equations and damage model parameters were then verified by the numerical simulations of the compression tests on the Body Centered Cubic lattices produced using the same EBM parameters with the solid EBM samples. In addition, a compression flow stress equation was extracted from the small-size test specimens (1 and 2 mm diameter) taken directly from the struts of the as-built lattices. The microscopic observations, XRD analyses and hardness tests confirmed the presence of α′ phase in the EBM solid samples and in the struts of the BCC lattices, which reduced the ductility of the EBM solid specimens and struts compared to the conventional Ti64. Furthermore, the partially melt particles on the surfaces of the struts acted as the stress concentration sides for micro-cracking; hence, the compression flow stresses of the struts were found to be significantly lower than those of the as-built EBM solid specimens. The flow stress equation derived from the struts predicted more accurately the compression behavior of the lattices. The compression tests and models showed that early damage formation in the lattices was noted to decrease the initial peak and post-peak stresses. As with the experiments, the initial damage occurred in the models with the separation of the nodes at the lattice cell surface edges. This resulted in an abrupt reduction in the stresses after the peak stress. The numerical lattices without damage showed a localized lattice deformation at the mid-sections and the stress increased continuously as a function of normal strain.

Microstructure of TiAl Capsules Processed by Electron Beam Powder Bed Fusion Followed by Post-Hot Isostatic Pressing.

The microstructures of intermetallic γ-titanium aluminide (TiAl) alloys are subjected to a certain degree of Al evaporation when processed by electron beam powder bed fusion (EB-PBF). The magnitude of the Al-loss is mainly correlated with the process parameters, and highly energetic parameters produce significant Al evaporation. The Al-loss leads to different microstructures, including the formation of inhomogeneous banded structures, thus negatively affecting its mechanical performance. For this reason, the current work deals with creating EB-PBFed TiAl capsules with the inner part produced using only the pre-heating step and melting parameters with low energetic parameters applying high beam speed from 5000 to 3000 mm/s. This approach is investigated to reduce the Al-loss and microstructure inhomogeneity after hot isostatic pressing (HIP). The results showed that the HIP treatment effectively densified the capsules obtaining a relative density of around 100%. After HIP, the capsules produced with the inner part melted at 3000 mm/s presented a lower area shrinkage (around 6.6%) compared to the capsules produced using only the pre-heating step in the core part (around 20.7%). The different magnitudes of shrinkage derived from different levels of residual porosity consolidated during the HIP process. The HIPed capsules exhibited the presence of previous particle boundaries (PPBs), covered by α2 phases. Notably, applying low energetic parameters to melt the core partially eliminates the particles' surface, thus reducing the PPBs formation. In this case, the capsules melted with low energetic parameters (3000 mm/s) exhibited α2 concentration of 3.5% and an average size of 13 µm compared to the capsules produced with the pre-heating step in the inner part with an α2 around 5.7% and an average size around 23 µm. Moreover, the Al-loss of the capsules was drastically limited, as determined by X-ray fluorescence (XRF) analysis. More in detail, the capsules produced with the pre-heating step reported an atomic percentage of Al of 48.75, while using low energetic melting parameters led to 48.36. This result was interesting, considering that the massive samples produced with standard parameters (so more energetic ones) revealed atomic Al percentage from 48.04 to 47.70. Finally, the recycled small particles showed a higher fraction of α2 phases with respect to the coarse particles, as determined by X-ray diffraction (XRD).

Runoff Simulation and Climate Change Analysis in Hulan River Basin Based on SWAT Model

The shortage of water resources is a long-standing constraint on the development of the Chinese economy and society. In this paper, the climate change occurring in Hulan River Basin is analyzed using the data collected at Wangkui Meteorological Station from 1960 to 2020. The overall temperature in the basin shows an upward trend, with a cumulative increase of 1.6 °C, as does the precipitation, which reaches 566.2 mm. In contrast, there is a downward trend shown by wind speed, with a cumulative decrease of 1.313 m/s. GIS remote sensing technology is applied to build a SWAT distributed hydrological model for the purpose of conducting runoff simulation in Hulan River Basin, and SWAT-CUP software is used to correct and analyze the simulation results. The parameters of snow melt are set to improve the accuracy of the model. The runoff data collected from Lanxi Hydrological Station from 2008 to 2020 are used to verify the model. The results show that the efficiency coefficient (NES) and correlation coefficient (R2) are 0.75 and 0.84, respectively, in the validation period from 2010 to 2013, while they are 0.77 and 0.93, respectively, in the correction period from 2014 to 2016, meeting the criteria of model evaluation. It can be seen from results noted above that SWAT is applicable in Hulan River Basin, providing a certain reference for the management of hydrological and water resources available in this region and for the construction of a distributed hydrological model of rivers in those high-latitude cold regions.

Laser Melting of Prefabrication AlOOH-Activated Film on the Surface of Nodular Cast Iron and Its Associated Properties.

This study aimed to improve the absorption rate of laser energy on the surface of nodular cast iron and further improve its thermal stability and wear resistance. After a 0.3 mm thick AlOOH activation film was pre-sprayed onto the polished surface of the nodular cast iron, a GWLASER 6 kw fiber laser cladding system was used to prepare a mixed dense oxide layer mainly composed of Al2O3, Fe3O4, and SiO2 using the optimal laser melting parameters of 470 W (laser power) and 5.5 mm/s (scanning speed). By comparing and characterizing the prefabricated laser-melted surface, the laser-remelted surface with the same parameters, and the substrate surface, it was found that there was little difference in the structure, composition, and performance between the laser-remelted surface and the substrate surface except for the morphology. The morphology, structure, and performance of the laser-melted surface underwent significant changes, with a stable surface line roughness of 0.9 μm and a 300-400 μm deep heat-affected zone. It could undergo two 1100 °C thermal shock cycles; its average microhardness increased by more than one compared to the remelted and substrate surfaces of 300 HV, with a maximum hardness of 900 HV; and the average friction coefficient and wear quantity decreased to 0.4370 and 0.001 g, respectively. The prefabricated activated film layer greatly improved the thermal stability and wear resistance of the nodular cast iron surface while reducing the laser melting power.

Redefined interface error, 2D verification and validation for pure solid-gallium phase change modeling by enthalpy-porosity methodology

For simulating phase change process of pure solid gallium, previously published literature contains some key problems, including the inappropriate definition & computation for interface errors, and the unsatisfactory numerical verifications & validations. Herein, the 2D verifications and 2D validations for the enthalpy-porosity modeling of pure gallium melting starting from a vertical end wall have been reported comprehensively. The well-known and classic experimental data presented in literature are used to verify and validate the model. The groundbreaking contributions in this work are that: i) The definition and computational method of the interface-position errors between the numerical and experimental results are revisited and proven carefully; ii) The numerical schemes as well as major parameters of 2D modeling gallium melting are selected with overall interface error <9%. However, these schemes and parameters are not appropriate for the solidification modeling of gallium due to the irregular and non-reproducible interface shapes caused by highly anisotropic properties of solid crystal gallium as experimentally reported in literature; iii) The 2D validations of enthalpy-porosity modeling of gallium melting are investigated in detail, and the maximum interface error is within the limits of ±12%. Moreover, the simulated liquid volume fractions and dimensionless heat transfer coefficients are well correlated in terms of related criteria parameters, and they are compared with correlations available in literature. It is concluded that to solidly validate the modeling of pure metal melting, both the global parameters (e.g., volume-averaged liquid fraction) and the local parameters (e.g., interface position) need to be considered together.

Significance of melting heat in bioconvection flow of micropolar nanofluid over an oscillating surface

Pharmaceuticals, biological polymer synthesis, eco-friendly uses, sustainable fuel cell innovations, microbial-enhanced extraction of petroleum, biological sensors, biological technology, and continual mathematical modeling refinement are all examples of how bioconvection is applied. This study examines the bio convectional viscoelastic-micropolar nano liquid flow with non-uniform heat sink/source, motile microorganisms that move across a stretched sheet. Thermal radiation and thermal conductivity are also explored. Brownian and thermophoresis diffusion effects are taken into account. The system of a higher partial differential equation is transformed to ODEs by using the appropriate similarity functions. Such reported equations are implemented with the computational tool MATLAB shooting approach using a bvp4c solver. The variations of numerous flow parameters comprise velocity, temperature, concentration, and motile microorganism profile. Various important, interesting transport numbers are numerically and graphically demonstrated with physical justifications. The bouncy ratio parameter reduces the fluid's velocity profile whereas the material parameter increases it. For increased melting parameters, the micro rotation profile improves, but it deteriorated. For the Prandtl number and temperature ratio parameters, the temperature profile is negative. The melting parameter influences the concentration profile. The microorganism’s profile is decreased bioconvective Lewis numbers and is higher for the magnetic parameter. The current model has many features in the manufacturing industries, engineering works, physics, and applied mathematics.

Determination of Strength Characteristics of Basalt Composite in COMSOL Multiphysics

Some strength characteristics of basalt melt, and basalt fiber are considered. The analysis of micromechanics and stress analysis is carried out on the example of composite cylindrical reinforcement based on multilayer and equivalent single-layer theory. The distributions of the stress wave field of three different values of natural frequencies and mode shapes in three samples of objects from the melt of basalt and basalt fiber are studied using the COMSOL Multiphysics software package. It has been established that three parameters of basalt fiber and basalt melt mainly influence the natural frequency and shape of the modes: these are the volume fraction, the density of the basalt fiber and the density of the basalt melt. It has also been found that the concentration of basalt melt, and basalt fiber affect the strength of the composite material.

Machine vision-based multi-degree-of-freedom laser cladding system integration and process monitoring research

Abstract Machine vision-based multi-degree-of-freedom laser cladding system integration and process monitoring is an important methods to ensure high-quality laser cladding. In this paper, based on the basic theory of multi-degree of freedom of machine vision, the laser cladding system is redesigned, and the melt pool images during the cladding process are monitored and analyzed. The melt pool image is pre-processed with the help of spatial filtering, and the image is thresholded using the iterative method thresholding to analyze the melt pool image. It is proved that the larger the laser power is, the larger the melt pool area is, and the maximum melt pool area is 60,000 pix when the laser power is 200 W. The maximum melt pool area is achieved when the nozzle tilt angle is 30° and the melt pool area is vertical. The smaller the melting speed, the larger the melting area and the maximum melting pool area is up to 35000pix when the melting speed is 210mm/min. It shows that the integration and process monitoring of the multi-degree-of-freedom laser melting system based on machine vision can reasonably control the process parameters of laser melting and improve the quality of laser melting by real-time monitoring and analysis of the melting pool images.

MODELLING THE PROCESS OF OXIDISING IMPURITIES IN A METAL BATH USING COHERENT NOZZLES

The main task of the oxygen-converter process is to produce a liquid metal semi-product with specified properties. It is directly related to the optimization of the blowing mode and devices responsible for the process and technical and economic parameters of melting. The effectiveness of the organization of the process of introducing oxygen into the melt, and, accordingly, assimilation by the metal bath basically depends on the design of the lance nozzles. In electrometallurgy, coherent nozzles are used to improve bath mixing performance and activate processes (a central nozzle for supplying oxygen and a peripheral one surrounding it for supplying gas as a fuel that forms an enveloping flame). Therefore, the authors conducted a study of the influence of coherent top nozzles on the oxidation of impurities in the metal bath under the conditions of the use for the oxygen-converter process (with oxygen supplied to both parts of the nozzle). A high-temperature simulation of the oxidation process of Si from hot metal was carried out by using a Cu-Zn melt (1%) when comparing blowing through a nozzle of a coherent type with a peripheral part of 75% and a conventional nozzle of the equivalent diameter.

Enhancement of a quasi-analytical solution for modelling additive manufacturing processes

Numerical modelling methods (e.g. finite element) can provide accurate descriptions of long-range temperature fields in laser or electron-beam melting processes, however the high computational costs at part-scale make them unsuitable for process modelling in additive manufacturing (AM). Alternative methods such as semi-analytical solutions based on a moving heat source reduce the computational expense but at the cost of unrealistic assumptions. Radiation, temperature-dependent physical properties and latent heat are not considered in the semi-analytical approach but can have a significant effect on the thermal history. In this study, the error associated with each of these contributions are assessed against the conduction-only semi-analytical solution for a range of processing parameters for surface melting on solid Ti-6Al-4V. The semi-analytical model is then “enhanced” using results from finite element simulations to better account for the heat transfer in the AM process.

Evaluation of Selected Technological Parameters for Selective Laser Melting of AlSi10Mg Metal Powder

Reusing the powder across consecutive route cycles is typical in a Selective Laser Melting (SLM) process since it is more sustainable and cost-effective. The theoretical part of the paper is oriented on the explanation of the SLM method principle, construction, and parameters of the device Renishaw AM250 used for manufacturing samples made of AlSi10Mg aluminium alloy. The experimental part focuses on evaluating powders that had been used in the process for a long time with periodic &#8216;rejuvenation&#8217;. The main aim will be to monitor whether the samples will be affected and if they achieved the required quality of mechanical properties and compare results with virgin powder and manufacturer sheets for virgin powders. The experimental part further describes the procedures and analysis of the microstructure of the samples. AlSi10Mg aluminium alloy was chosen because of an assumption that it will be sensitive to increased oxygen content. A strong affinity for oxygen uptake exists in AlSi10Mg. Therefore, preventing the contamination, careful handling is required.

Main Characteristics of Processed Grain Starch Products and Physicochemical Features of the Starches from Maize (Zea mays L.) with Different Genotypes.

To understand the relationship between the genotype of maize plants and differences in their origin and the ploidy of the genome, which carry gene alleles programming the biosynthesis of various starch modifications, the thermodynamic and morphological features of starches from the grains of these plants have been studied. This study investigated the peculiarities of starch extracted from subspecies of maize (the dry matter mass (DM) fraction, starch content in grain DM, ash content in grain DM, and amylose content in starch) belonging to different genotypes within the framework of the program for the investigation of polymorphism of the world collection of plant genetic resources VIR. Among the starch genotypes of maize studied, four groups comprised the waxy (wx), conditionally high amylose ("ae"), sugar (su), and wild (WT) genotypes. Starches with an amylose content of over 30% conditionally belonged to the "ae" genotype. The starches of the su genotype had fewer starch granules than other investigated genotypes. An increase in amylose content in the investigated starches, accompanied by a decrease in their thermodynamic melting parameters, induced the accumulation of defective structures in the starches under study. The thermodynamic parameters evaluated for dissociation of the amylose-lipid complex were temperature (Taml) and enthalpy (Haml); for the su genotype, temperature and enthalpy values of dissociation of the amylose-lipid complex were higher than in the starches from the "ae" and WT genotypes. This study has shown that the amylose content in starch and the individual features of the maize genotype determine the thermodynamic melting parameters of the starches under study.

ANTICANCER EFFECT OF AgTOEPyP4 PORPHYRIN

The silver-containing porphyrin Ag-meso-tetra(4-N-hydroxyethylpyridyl)porphyrin (AgTOEPyP4) was investigated as a potential anticancer drug using spectrophotometric, calorimetric and electrophoretic measurements. The studies were conducted on healthy, cancer-induced, and treated by AgTOEPyP4 white mice. DNA was isolated from the liver and tumor tissues of mice. Melting curves were studied in the presence of various stoichiometric concentrations of Mn2+ ions. The character of the DNA–Mn2+ interaction in the tumor differs from that in the norm due to defects in the secondary structure of tumor DNA, which is expressed in the DNA melting characteristics of DNA. It was revealed that the melting parameters, enthalpy, and electrophoretic mobility of DNA isolated from the tumor-bearing mice tissues differed from healthy DNA. It was shown that all studied parameters of the DNA isolated from the liver and tumor treated by AgTOEPyP4 mice approached the norm. The obtained results revealed that AgTOEPyP4 porphyrin has a pronounced therapeutic effect against sarcoma S180 and requires further investigation as an anticancer drug.

Multiresponse Optimization of Selective Laser Melting Parameters for the Ni-Cr-Al-Ti-Based Superalloy Using Gray Relational Analysis

The selective laser melting technology is of great interest in the aerospace industry since it allows the implementation of more complex part geometries compared to the traditional technologies. This paper presents the results of studies to determine the optimal technological parameters for scanning a Ni-Cr-Al-Ti-based superalloy. However, due to a large number of factors affecting the quality of the parts obtained by selective laser melting technology, the optimization of the technological parameters of the scanning is a difficult task. In this work, the authors made an attempt to optimize the technological scanning parameters which will simultaneously correspond to the maximum values of the mechanical properties ("More is better") and the minimum values of the dimensions of the microstructure defect ("Less is better"). Gray relational analysis was used to find the optimal technological parameters for scanning. Then, the resulting solutions were compared. As a result of the optimization of the technological parameters of the scanning by the gray relational analysis method, it was found that the maximum values of the mechanical properties were achieved simultaneously with the minimum values of the dimensions of a microstructure defect, at a laser power of 250 W and a scanning speed of 1200 mm/s. The authors present the results of the short-term mechanical tests for the uniaxial tension of the cylindrical samples at room temperature.

In-situ synthesis of CoCrFeMnNi high-entropy alloy by selective laser melting

The CoCrFeMnNi high-entropy alloy is considered to be one of the excellent potential material for metal additive manufacturing. In this study, Elemental powders of Co, Cr, Fe, Mn, Ni were blended for bulk samples fabricating to study microstructure, phase composition and mechanical properties. The blended powder shows good printability with various selective laser melting (SLM) parameters and the as-built high-entropy alloy (HEA) samples achieve a reliable forming quality. It has been shown that the as-built HEA presents a single Face Centered Cubic (FCC) matrix and few residual Cr particles, and FCC matrix exhibits a typical hierarchical microstructure. The bulk samples were produced using 320 W laser power, 750 mm/s scan speed and 0.09 mm hatch distance show the best strength and toughness matching. The study has verifified the feasibility of using blended powder to prepare high-quality HEA by SLM.

Response of glacier modelling parameters to time, space, and model complexity: Examples from eastern slopes of Canadian Rocky Mountains

Mountain glaciers are at risk of rapid retreat and require an accurate prediction of their melt and evolution. However, there is a great deal of hassle with mountain glacier melt modelling at a regional scale. Most advanced physical process-based models require an ample amount of high-resolution measurements, while widely-used empirical models suffer from parameter transferability. We developed a glacier melt, mass balance, and evolution modelling framework using three temperature index melt modelling approaches. We performed 24 model scenarios to examine the response of 19 empirical parameters to the effects of: (1) two time periods, for understanding how parameter response can vary with time period considered for the simulation; (2) two glaciers located at the eastern slopes of the Canadian Rocky Mountains, for understanding the effects of glaciers hydro-climate and geographic setting; and (3) two levels of complexity in the model structure including melt and mass balance models coupled with (complex) and without (simple) glacier evolution modules. The results showed that the best optimal melt parameter sets vary temporally and spatially for both simple and complex models, indicating that they are not transferable from one period to another and across glaciers. The variations of ice melt parameters are greater than the snowmelt parameters. The spatiotemporal variations of parameters are resulted from the geographical and local climatic settings and energy balance components, including albedo parameterization on the glacier surface, the altitudinal variations of the glaciers, and the slope and aspects to which glaciers are exposed. For all models, the most sensitive parameter is temperature Lapse rate (LR), but with increasing model complexity, the parameter responses vary depending on the melt model structure and input data. Our study provides important information for modelling glacier melt and evolution at a regional scale.

Study of electron beam refining of metals by modelling of heat processes

The development and application of heat mathematical models and simulation tools, taking into account peculiarities of the investigated metals enable a more precise determination of the effect of the electron beam melting parameters (beam power, residence time, etc.) on the quality of the refined metal, to assess the relation between the processes and the material properties, as well as to formulate recommendations regarding the controlled parameters for increasing the efficiency of the technological e-beam melting and refining process. In this work, developed time-dependent simulation tool for heat transfer modeling at e-beam melting, aiming to aid understanding and optimizing electron beam refining process of metals materials, is applied for melting of different metals (tantalum, copper, and titanium). The model is validated using experimental data for the melted pool geometry and results are discussed.