Metallurgy Method Research Articles

Microstructure and hydrogen storage properties of the Mg2−xYxNi0.9Co0.1 (x = 0, 0.2, 0.3, and 0.4) alloys

Rare earth elements have excellent catalytic effects on improving hydrogen storage properties of the Mg2Ni-based alloys. This study used a small amount of Y to substitute Mg partially in Mg2Ni0.9Co0.1 and characterized and discussed the effects of Y on the solidification and de-/hydrogenation behaviors. The Mg2−xYxNi0.9Co0.1 (x = 0, 0.2, 0.3, and 0.4) hydrogen storage alloys were prepared using a metallurgy method. The phase composition of the alloys was studied using X-ray diffraction (XRD). Additionally, their microstructure and chemical composition were studied using scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. The hydrogen absorption and desorption properties of the alloys were studied using pressure-composition isotherms and differential scanning calorimetric (DSC) measurements. The structure of the as-cast Mg2Ni0.9Co0.1 alloy was composed of the peritectic Mg2Ni, eutectic Mg–Mg2Ni, and a small amount of pre-precipitated Mg–Ni–Co ternary phases, and was converted into the Mg2NiH4, Mg2Ni0.9Co0.1H4, and MgH2 phases after hydrogen absorption. Furthermore, the XRD patterns of the alloys showed the MgYNi4 phase and a trace amount of the Y2O3 phase along with the Mg and Mg2Ni phases after the addition of Y. After hydrogen absorption, the phase of the alloys was composed of the Mg2NiH4, MgH2, MgYNi4, YH3, Y2O3, and Mg2NiH0.3 phases. With the increase of Y addition, the area ratios of the peritectic Mg2Ni matrix phase in the Mg2−xYxNi0.9Co0.1 (x = 0, 0.2, 0.3, and 0.4) alloys gradually decreased until they disappeared. However, the eutectic structure gradually increased, and the microstructures of the alloys were obviously refined. The addition of Y improves the activation performance of the alloys. The alloy only needed one cycle of de-/hydrogenation to complete the activation for x = 0.4. The DSC curves showed that the initial dehydrogenation temperatures of Mg2Ni0.9Co0.1 and Mg1.8Y0.2Ni0.9Co0.1 were 200 and 156 °C, respectively. The desorption activation energies of the hydrides of the Mg2Ni0.9Co0.1 and Mg1.8Y0.2Ni0.9Co0.1 alloys calculated using the Kissinger method were 94.7 and 56.5 kJ/mol, respectively. Moreover, the addition of Y reduced the initial desorption temperature of the alloys and improved their kinetic properties.

Effects of Cu on the microstructure and hydrogen storage properties of Mg-20Ni alloy

In order to improve the hydrogen storage capacity of hypereutectic Mg-Ni alloy, the Mg40Ni10 and Mg40Ni8Cu2 alloys were prepared by metallurgy method. The effects of Cu on the alloys’ phase composition, microstructure were studied systematically. The volumetric Sieverts’ method was used to test and analyze the activation performance and hydrogen absorption and desorption kinetic performance of the alloys. It was found that the partial substation of Ni in the Mg2Ni-riched matrix alloy with Cu can change the primary Mg2Ni and eutectic Mg-Mg2Ni morphology of the alloy. With the doping of Cu content, although the activation property of the alloy decreases, the hydrogen storage capacity as well as the kinetic of hydrogen absorption and desorption are improved significantly.

Occurrence and screening- flotation separation for the beneficiation of rare earth elements and yttrium (REY) in core sediments from the Pacific Ocean

Rare earth elements (REE) and yttrium (termed as REY), as a significant strategic resource, are recently found to be extremely enriched in deep-sea sediments, which is expected to be an important REY resource in the future. However, the efficient development and utilization of deep-sea REY-rich sediments are greatly limited by the current common beneficiation and metallurgy method. In this study, detailed grain size analysis, mineral identification and geochemical measurement aiming at deep-sea sediments collected from a station in the Central Pacific Basin were employed to determine the occurrence of deep-sea REY-rich sediments. Based on that, the Screening-flotation separation was adopted to achieve efficient enrichment of REY in the sediments. The ΣREY contents in the samples can reach 790 ppm, and sieve analysis reveal that bioapatite (fish teeth and bones) and Fe-Si-Mn oxide (oxyhydr) on the micro-nodule surface are the major REY carriers. About 87.27% REY was scavenged by bioapatite fossils. The REE patterns show distinct negative Ce/Ce* and slightly positive Eu/Eu* anomalies, similar to the Western and central North Pacific seawater, indicating a promising source of REY in the samples may be pore water in sediments, taking into account other studies as well. The grain size analysis suggests that REY enrichment can be achieved by removing the fine-grained particles (<15 μm). Screening-flotation separation, as a newly developed approach for the beneficiation, uses the pre-screening method to pre-detach the clay-size fraction (<15 μm), and combines flotation and magnetic separation, which further upgrades REY concentrate to achieve about 9 times enhancement of REY recovery from marine sediments. Although further research is needed, the study we determined can provide reference for industrial exploitation of rare earth resources in deep-sea REY-rich sediments.

Study on physical properties of Al2O3-based slags used for the self-propagating high-temperature synthesis (SHS) – metallurgy method

Abstract The Al2O3-based slags are playing important roles in the preparation of Cu–Cr alloy through self-propagating high-temperature synthesis (SHS) – Metallurgy method. However, the current research on Al2O3-based slag is mainly concentrated on steel metallurgical slag and electroslag remelting slag, and the research on aluminum thermal reduction slag with high content of Al2O3 is still insufficient. Therefore, systematic studies of the physical properties of slag with high aluminum content were carried out in the present work, and the influence of CaF2, CaO, MgO, SiO2, and Na3AlF6 on viscosities, liquidus temperatures, densities, and surface tensions of high Al2O3 content slags was measured and analyzed. The results indicated that CaO and CaF2 have positive effects on the physical properties of Al2O3-based slags, MgO has positive effects when its content is not over 3%, and SiO2 and Na3AlF6 have negative impacts. CaO, CaF2, and MgO (not over 3%) could be used as additives to improve the metallurgical performance of Al2O3-based slags in aluminothermic reduction–slag refining method.

Weak donor-like effect to enhance the thermoelectric performance of Bi2Te2.79Se0.21 near room temperature

Bismuth telluride-based materials are the most celebrated thermoelectric (TE) materials near room temperature. However, for the n-type bismuth telluride-based materials, the traditional powder metallurgy (PM) method, such as grinding and ball milling, can induce strong donor-like effect. The strong donor-like effect boosts the carrier concentration [Formula: see text] and the carrier thermal conductivity [Formula: see text], leading to the deterioration of both electrical and thermal performance. Herein, the basal deformation (BD) has been performed in the n-type Bi2Te3-based materials to introduce weak donor-like effect. The BD crystalline bulks were obtained through sintering the stacked crystals, which had been heavily deformed on the (00[Formula: see text] plane. The BD process optimizes the carrier concentration [Formula: see text] and improves the power factor (PF). Meanwhile, the lattice thermal conductivity [Formula: see text] is suppressed due to the enhanced grain boundary scattering. Consequently, a peak ZT of 1.0 at 380 K has been achieved in Bi2Te[Formula: see text]Se[Formula: see text], which is 24% and 30% higher than that of the original zone-melting (ZM) ingot and the polycrystalline sample by PM. This study sheds light on the further TE performance enhancement of bismuth telluride-based materials via introducing the weak donor-like effect.

Determination of the pressure inside pores

Determination of the porosity, structural characteristics of pores, and gas pressure in closed pores is the most important part of assessing physical and mechanical properties of materials. The internal pressure inside the pore can be used in estimating the level of strength reliability of the porous volume of the product to optimize the technological processes of product manufacturing, control their structure and properties, and avoid the formation of cracks at the boundaries of the particles consisting the material. We present a method for calculating the internal pressure in a spherical pore that has arisen in the material of a product obtained using powder metallurgy or additive technologies. The proposed procedure for measuring internal pressure in a pore consists in application of an external pressure to the product, measurements of the displacements of the points on the pore surface, and calculation of the internal pressure from the difference between the displacements. In this case, the known solutions of the problem of the theory of elasticity regarding the deformation of a spherical cavity located in the center of a spherical hollow ball are used. The results obtained can be used to assess the properties and structure of the products obtained by additive technology and methods of powder metallurgy, as well as to improve the technology of their manufacture.

A Study on Mechanical and Tribological Properties of Aluminum 7075 MMCS Reinforced with Silicon Carbide and Coconut Husk by Powder Metallurgy Process

The metal matrix composite strengthened with ceramic material of silicon carbide has smart mechanical characteristics. Metal-based composites, however, demand progress in their friction and tribological characteristics. In this work-study an effort is made to design a completely new material through the method of metallurgy by adding Coconut husk. This study explored the effect of coconut husk on the tribological behavior of hybrid composite Al 7075/5 wt. % Sic/Xwt. %coconut husk(X=6,4 and0).The research confirms the performance of wear properties by incorporating coconut husk into the composite. The sic-coconut husk reinforced Al 7075 (aluminum alloy 7075) was studied. Metallurgy route was used to prepare the composites. Microstructures, the mixture of materials, wear and wear resistance properties were analyzed by optical micro cope and scanning electron microscope.

Investigation of the effect of addition of boron nitride on microstructure and mechanical properties of cast iron brake materials used in railway vehicles

In this study, characterization of cast iron break shoes used in locomotives and the effect of BN addition and BN addition on microstructure and mechanical properties by using powder metallurgy (PM) method by adhering to the chemical composition of cast iron break shoes were investigated. In this context, cast iron sabers were chemically analyzed and all elements were supplied in powder form, and then BN added powder compositions were produced by cold and hot pressing technique. A total of 4 different compositions were created without BN, with 0.25, 0.5 and 1 % BN addition. Cold pressing was made in a steel mold with a diameter of 10 mm under 700 MPa pressure under room conditions. Hot pressing was carried out in a graphite mold with a diameter of 15 mm in an argon atmosphere under a pressure of 45 MPa at a temperature of 900 °C. Then the cold and hot pressed samples were sintered at 1 200 °C for 2 hours in argon atmosphere. Density measurement of the produced compositions, microstructure examination, micro hardness measurement were made. Generally, in density measurements, the densities of the samples subjected to hot pressing were higher than the cold pressing process. The hardness value decreased in parallel with the addition of BN. Keywords: Brake shoe; powder metallurgy; microstructure; mechanical properties

Влияние механической активации порошка ВК-8 на свойства спеченных твердых сплавов

Introduction. For the manufacture of wearproof tools and machine elements, the method of powder metallurgy is widely used. The preliminary high-intensity mechanical activation of the powder is used to improve the structure and properties of the alloy obtained by the method of powder metallurgy. The mechanical activation can result in formation of nanostructures with subsequent amorphization of the material, can bring phase transformations, it can certainly affect the properties of the material. However, mechanical treatment does not always lead to a positive result. Therefore, the study of the effect of mechanical activation of WC-based powder on the properties of sintered alloys is important. Purpose of the work: to study the effect of high-intensity mechanical activation of WC-based powder on the structure and properties of sintered samples. The work investigates alloys obtained by the method of powder metallurgy, using mechanically activated powders for 10 to 300 seconds in a planetary ball mill. Materials and methods. The alloys are obtained by cold one-sided pressing followed by sintering at a temperature of 1400 °C in a vacuum furnace. Particle morphology of powder and structure of alloys is analyzed by scanning electron microscopy method. The metallographic analysis of the alloys is carried out by optical microscopy. Phase analysis and the parameters of the crystal structure are performed by X-ray diffraction. The hardness of the sintered samples is measured by hardness tester. Results and its discussion. It is shown that after sintering of powders alloys with WC and Co phases are formed. The lattice parameter of the WC-phase correlates well with values in literature. A second carbide phase, Co3W3C, is formed in the samples upon mechanical activation for more than 100 sec. The minimum porosity of sintered sample is 7.8 ± 1 % that corresponds of sample with preliminary mechanical treatment for 30 seconds. It is shown that the hardness depends on grain size, porosity and second carbide content. Thus, mechanical activation can be effective for increasing the physical and mechanical properties and inhibiting grain growth, but in this case, it is necessary to carry out mechanical processing in the mechanical treatment time range 60-100 sec.

Bulk Grain-Boundary Materials from Nanocrystals

<h2>Summary</h2> Grain-boundary engineering is pivotal to fully utilize the mechanical, electrical, and thermal-transport properties of various materials. However, current methods in metallurgy rely almost exclusively on top-down approaches, making precise grain-boundary engineering, especially at nanoscale, difficult to achieve. Herein, we report a method to produce tailored grain-boundary conditions with nanoscale precision from colloidal metal nanocrystals through surface treatment followed by a pressure-sintering process. The resulting bulk grain-boundary materials (which we call "nanocrystal coins") possess a metal-like appearance and conductivity while inheriting the original domain features of the nanocrystal building blocks. Nanoindentation measurements confirmed the superior mechanical hardness of the obtained materials. Further, we use this method to fabricate, for the first time, a single-component bulk metallic glass from amorphous palladium nanoparticles. Our discovery may spur the development of new materials whose functionality crucially depends on the domain configuration at nanoscale, such as superhard materials, thermoelectric generators, and functional electrodes.

Machining behaviors of nickel titanium composite using non-traditional machining processes

The research work is related to nickel titanium composite that has been increased due its admirable substance properties. The present research concluded that the nickel and titanium is reinforced with boron carbide prepared by metallurgy method. The synthesized composite is processed under different testing for evaluation of substance properties. Subsequently, the accumulation of boron carbide, the substance properties has been greatly improved. Non-traditional machining processes like Spark Erosion Machining (SEM) and Laser Beam Machining (LBM) are carried out to evaluate the machining behaviors such as. In each non-traditional machining process, the prominent factors effect is examined through variance analysis. In EDM process, the current is offered the utmost effects (83.28%) on MSR. In LBM process, the cutting speed is top most effects (90.27%) on material subtraction rate followed by gas pressure (6.21%).

ПРОБЛЕМЫ РАЗВИТИЯ ЛИТЬЯ ПОД ДАВЛЕНИЕМ ТВЕРДОЖИДКОГО МЕТАЛЛА В РОССИИ

The methods of powder and granular metallurgy are rapidly improving, granulation and spheroidization of solid phase particles is carried out “in–situ” at the stage of alloy preparation, which precedes the casting stage, and on this basis, a new generation of technologies is born and developed. dubbed Thixo – (casting, molding, forming) and PowderInjectionMolding (РIM (МIM, СIM)) technologies. All of the above technologies are united by the term Semi–Solid Processing (SSP), and the mandatory code prefixes Semi–Solid Metal (SSM) and MetalInjectionMolding (MIM) have appeared in the designations of alloys prepared for processing in a solid–liquid state.

ТЕХНОЛОГИЧЕСКИЕ ПУТИ СОЗДАНИЯ КОМПОЗИЦИОННЫХ МАТЕРИАЛОВ НА ОСНОВЕ ЖАРОПРОЧНЫХ ТУГОПЛАВКИХ СОЕДИНЕНИЙ (обзор)

The article discusses the main technological approaches to obtain heat-resistant and heat-resistant materials based on compounds in the Ni–Al system in order to use them in promising products of aviation and rocket technology. It is shown that when receiving materials based on compounds in the Ni-Al system, a phase of eutectic origin is formed based on the Ni3Al compound, which reduces the technological plasticity of the alloys of this system. The use of powder metallurgy methods eliminates such phases in the structure of alloys obtained using granule metallurgy technology, as well as with the use of special methods of powder metallurgy. Technological approaches are presented to obtain similar materials using powder metallurgy methods combined with thermomechanical processing.

Study of the Effect of the Floating Die Compaction on Mechanical Properties of Titanium Foams

Titanium (Ti) and its alloys are used for biomedical applications because of their high resistance to corrosion, good strength-to-weight ratio, and high fatigue resistance. However, a problem that compromises the performance of the material is the mismatch between Young’s modulus of Ti and the bone, which brings about stress shielding. One strategy that has been investigated to reduce this difference is the manufacture of Ti-based foams, using powder metallurgy (PM) methods, such as the space-holder technique. However, in the uniaxial compaction, both non-uniform density distribution and mechanical properties remain because of the compaction method. This work studies the influence of compaction by adopting a floating-action die related to a single-action die (SAD), on the density of green and sintered Ti foams with porosities around 50 vol.% characterized by optical microscopy, ultrasound analysis, compression tests, and microhardness. The compaction process employing a floating-action die generates Ti foams with a higher density up to 10% with more control of the spacer particle added compared to the single-action die. Furthermore, compaction method has no relevant effect on microhardness and Young’s modulus, which allows getting better consolidated samples with elastic modules similar to those of human bone.

Dissolution Behavior of Al2O3 Inclusions in CaO-Al2O3 Based Slag Representing Aluminothermic Reduction Slag

In the preparation of CuCr alloy using the self-propagating high-temperature synthesis (SHS)-metallurgy method, the dissolution of alumina in molten slag has an important influence in two key steps: aluminum thermal reduction and slag refining. In the present work, the dissolution behavior of Al2O3 into molten SHS-metallurgical slags was investigated by employing the rotating cylinder method and static dissolution method. It is concluded that the increase of MgO, CaF2, CaO, and Na3AlF6 contents can increase the dissolution rate of alumina in SHS-metallurgical slag, and the order of influence is from strong to weak. Both temperature and rotating speed can increase the dissolution rate, and the rate-limiting step is the diffusion of alumina in the boundary layer, with the solid alumina first reacting with lime to form two intermediate phases, CaO·2Al2O3 and CaO·6Al2O3, and finally dissolving into the slag in the form of an aluminum polymer.

Microstructure and Corrosion Behavior of Hot-Forged Duplex Stainless Steels Sintered in Partial Vacuum and Hydrogen Atmospheres

In this investigation, two duplex stainless steels (DSS), namely DSS A and DSS B, were made by pre-alloyed powders such as 310L and 430L using the method of powder metallurgy. Chromium, nickel and molybdenum were added with pre-alloyed stainless steel powders in appropriate proportions to obtain duplex composition. Two DSS composition powders were sintered at 1350 °C in two different atmospheres, i.e., partial vacuum and hydrogen. Sintered compacts were forged at the temperature of 1150 °C and quenched in water immediately. Forged DSS were observed and analyzed for densification, microstructural examination, ferrite count and pitting corrosion. For both the compositions (DSS A and DSS B), forged density is in the range of 7.73–7.79 g/cc. Microstructure of DSS A (partial-vacuum-sintered) revealed acicular and angular types of ferritic grains along with austenitic phase. DSS B revealed elongated (cell structure) ferrite grains of various sizes along with random orientation. Partial-vacuum-sintered steels contain more ferrite volume than hydrogen-sintered steels. The lowest current density of 3.04 E-5 mA/cm2 and the highest linear polarization resistance of 46,882 Ωcm2 have been exhibited for the hydrogen-sintered DSS B composition.

Investigation of the Influence of Technology of Production of Cathodes on the Quality of Condensation Heat-Resistant Coatings

We present the results of comparative investigations of the quality of Me???Cr???Al???Y tube cathodes obtained by the methods of casting and granule metallurgy. The quality of coatings applied to turbine blades by the method of ion-plasma deposition is evaluated by the method of X-ray diffraction microanalysis. The influence of the technology of production of cathodes on the surface roughness of the coatings of turbine blades is analyzed. The surface quality of the blades with heat-resistant coatings deposited with the use of the investigated cathodes is estimated by the method of scanning electron microscopy. We also performed the quantitative analysis of the drop phase with its separation into fractions.

Mechanical and tribological properties of Al 7075 /SiC/ Graphite hybrid composites processed by powder metallurgy technique

The metal matrix composite strengthened with ceramic material of carbide (SiC) has smart mechanical characteristics. Metal-based composites, however, demand progress in their friction and tribological characteristics. In this work-study an effort is made to design a completely new material through the method of metallurgy by adding graphite, which acts as a solid lubricant. This study explored the effect of graphite on the tribological behaviour of hybrid composite Al 7075/5 wt. % SiC / X wt. % graphite (X=10, 5 and 0). The research confirms the performance of wear properties by incorporating graphite into the composite. The sic-graphite reinforced Al 7075 (aluminium alloy 7075) was studied. Metallurgy route was used to prepare the composites. Microstructures, the mixture of materials, wear and wear resistance properties were analyzed by optical micro cope and scanning electron microscope, XRD, and pin-on-disc apparatus. The freshly developed metal composite has significant improvement in tribological properties with a mixture 5% silicon carbide (SiC) and 5% graphite. The experimental investigations confirm that a sliding distance of one thousand meters and a sliding velocity of 1.5 m / s with an applied load of 5 N leads to minimum wear loss of 0.01062g and coefficient of friction as 0.1278

Properties Comparison of Ti-Al-Si Alloys Produced by Various Metallurgy Methods.

Melting metallurgy is still the most frequently used and simplest method for the processing of metallic materials. Some of the materials (especially intermetallics) are very difficult to prepare by this method due to the high melting points, poor fluidity, or formation of cracks and pores after casting. This article describes the processing of Ti-Al-Si alloys by arc melting, and shows the microstructure, phase composition, hardness, fracture toughness, and compression tests of these alloys. These results are compared with the same alloys prepared by powder metallurgy by the means of a combination of mechanical alloying and spark plasma sintering. Ti-Al-Si alloys processed by melting metallurgy are characterized by a very coarse structure with central porosity. The phase composition is formed by titanium aluminides and titanium silicides, which are full of cracks. Ti-Al-Si alloys processed by the powder metallurgy route have a relatively homogeneous fine-grained structure with higher hardness. However, these alloys are very brittle. On the other hand, the fracture toughness of arc-melted samples is immeasurable using Palmqvist’s method because the crack is stopped by a large area of titanium aluminide matrix.

The Investigation on Flow Behavior of Powder Metallurgy Ti-10V-2Fe-3Al Alloy Using the Prasad Stability Criterion

The hot deformation behavior of Ti-10V-2Fe-3Al alloy obtained by the powder metallurgy (PM) method was investigated. Material for the research was produced by blending of elemental powders followed by uniaxial hot pressing. Thermomechanical tests of Ti-10V-2Fe-3Al compacts were carried out to determinate the stress-strain relationships at the temperature range of 800 °C to 1000 °C and strain rate between 0.01 and 10 s−1. Based on the dynamic material model (DMM) theory, processing maps at constant strain value were developed using data obtained from hot compression tests. The processing maps were elaborated for the final strain value, which was 0.9, and with flow instability criterion domains applied to it. Two critical regions associated with the flow behavior of the investigated material were revealed. Microstructural changes during hot deformation at various temperatures and strain rates were discussed. The correlation between calculated efficiency of power dissipation, flow instability criterion, and microstructure evolution was determined. The presence of defects was confirmed in regions predicted by the instability maps. The microstructure of the investigated alloy, corresponding to the high efficiency of power dissipation characterized by the occurrence of dynamic recrystallization (DRX) phenomena, was also shown. Additionally, average hardness values in relation to variable process parameters were designated. Based on the conducted studies and analysis, processing windows for Ti-10V-2Fe-3Al alloy compacts were proposed.