Alloy Melt Research Articles

A qualitative and quantitative investigation of nonmetallic inclusions in molten Al–Mg, Al–Cu, and Al–Zn–Mg–Cu alloys

In this work, a qualitative and quantitative investigation on inclusions in molten Al–Mg, Al–Cu, and Al–Zn–Mg–Cu alloys, and the evolution behavior of inclusions in these three alloys during off-line and on-line purification steps were studied via the porous disc filtration technique. It was found that the removal of oxide from 2219 and 5A06 aluminum alloys melt via furnace refining is difficult, both of which can only remove the oxide by about 27 %, whereas the furnace refining can remove oxide from 7A04 aluminum alloy melt effectively, it can reduce the oxide by 55 %. Moreover, we determined that the furnace refining and degassing can reduce the boride content in 5A06 aluminum alloy effectively, but the boride content in 7A04 and 2219 aluminum alloy varied little after these two purification processes. Also, the furnace refining and on-line degassing were found to increase the carbide in 7A04 aluminum alloy, which was not found in the other two alloys. Further, we correlated the relationship between the slopes of the melt mass-time curves of the filtrates and the inclusion content for 2219, 5A06, and 7A04 aluminum alloys, which implies a higher concentration of inclusion possesses a lower slope for the melt mass-time curves of the filtrates. The obtained result could offer some guidelines for the production of high-quality ingot for the studied three alloys.

Influence of buoyancy on phase separation during laser melting of Silicon and Iron ore

Phase separation is a well-known effect in liquid-liquid interactions, which can also occur during laser-related processes such as laser melting and laser alloying. However, the mechanism of phase separation between immiscible liquids on a millimeter scale during rapid laser processes has not been fully investigated, in which the extent of buoyancy’s contribution to it has remained unclear. Therefore, this investigation focused on the effect of buoyancy on liquid phase separation during the laser melting of silicon (Si) and iron ore. A simplified 2D numerical model was established to simulate the motion of a single Si liquid droplet in iron ore melt with and without the impact of gravity, respectively. The rise velocity of the droplet was calculated and analyzed under the effect of gravity. In addition, the phenomena of simultaneous laser remelting of Si and iron ore in layers were recorded with a high-speed camera, and the element and phase distributions of the target nugget were analyzed by Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS). By combining the simulation, high-speed imaging, and SEM/EDS analysis, the effect of buoyancy on phase separation has been qualitatively analyzed. This investigation revealed that buoyancy is not the main driving force of liquid-liquid phase separation during rapid laser processing.

Застосування титану у вигляді фольги для натирання неметалевих матеріалів з метою їх змочування і паяння металевими припоями

Activation of filler metal alloys for brazing non-metals by introducing chemically active elements such as titanium, zirconium, etc. is a technically challenging task. This paper discusses some methods of brazing non-metallic materials with filler metal alloys. A brief review of publications on the metallisation of non-metallic materials by titanium friction for further brazing with filler metal alloys is given. Two types of titanium foil tools for friction coatings on non-metallic materials have been proposed and used, which, in comparison with friction with compact titanium, significantly reduce the destruction of the ceramic surface and facilitate their application. Samples of high-alumina ceramics A995 and WK94-1, were metallized by the proposed method. The wetting of ceramics coated with PSr72 filler alloy (copper-silver eutectic) was studied, brazed joints were obtained, and the microstructure of the metal-nonmetal contact zone was studied The main purpose of such a coating for brazing processes is to activate the filler metal alloys melt to wet the ceramic. The surface roughness of non-metals affects the microstructure of the applied coating. As the roughness decreases, the density of the coating increases. Studies of the microstructure of the brazed joint have shown that the PSr72 melt penetrates the titanium coating, saturates it with titanium and wets the ceramic. This means that such metallisation accelerates the saturation of the melt with titanium. The brazing modes of this method practically coincide with the brazing modes of titanium-containing filler metal alloys Using the method of friction the metallization layer reduces the cost of the brazing process. Keywords: rubbing with metals, titanium foil, soldering of ceramics, metal solders, microstructure.

Experimental Manufacturing of Ferromanganese Alloy from Man-Made Manganese-Containing Wastes

The results of experiments on manganese pellets based on beneficiated manganese-containing sludge and the melting of ferromanganese alloy with their use are presented. Via beneficiating manganese-containing sludge (16.32% Mn), a concentrate with a manganese content of 35.2% was obtained. The composition of the charge used to prepare manganese pellets is proposed, and the conditions affecting their strength are determined. It was established that manganese is present in the composition of calcined pellets in the form of jacobsite MnFe2O4 and hausmannite Mn3O4. The formation of a phase of ferrobustamite (Ca0.79Fe0.21)SiO3, a ferrosilico-calcium binder that helps increase the strength of pellets, was found. Ferromanganese alloy was obtained as a result of the melting of calcined manganese pellets in a high-temperature Tamman-type unit. The Fe-Mn-Si alloy corresponds to the DIN 17 564 as-grade FeMn70Si in terms of manganese (63.76%) and silicon (17.21%) contents. The content of limiting impurity elements—carbon and phosphorus—in ferromanganese alloy is within acceptable limits. The structure of Fe-Mn-Si alloy and slag formed during their smelting process were studied.

A distinctive kinetics transition from stable hcp to metastable fcc dendrite growth within liquid Re95W5 refractory alloy

ABSTRACT A transition of dendrite growth kinetics from stable hcp to metastable fcc phases was observed for refractory Re95W5 alloy in an electrostatic levitation state, which attained a liquid undercooling up to 872 K (0.26T L). Stable hcp dendrite dominated in the single recalescence for pure Re in the whole of its undercooling regime, but prevailed for Re95W5 alloy only in the specific range of 159–867 K undercooling. The rapid dendrite growth velocity displayed a power-law relationship with the degree of undercooling. Once the refractory alloy melt was undercooled beyond 867 K undercooling, metastable fcc dendrite grew primarily from the liquid phase in the first recalescence, which was followed by a complete ‘fcc to hcp’ solid-state transformation in the second recalescence. An abrupt change of growth kinetics took place to depress the dendrite growth velocity drastically from 41.8 m·s−1 for stable hcp phase at 867 K undercooling to 10.9 m·s−1 for metastable fcc phase at 872 K undercooling.

Metal-metal and metal-composite joints with 3D printed aluminium substrates: effect of surface treatment on the mode I fracture toughness

ABSTRACT Adhesive bonding of composite laminates to metals is an increasingly employed technique to manufacture lightweight structures. However, this type of joints is sensitive to defects and composite delamination near the bonded area. Thus, increasing their damage tolerance is fundamental to design reliable multi-material components. This work is the first step in a project aimed at improving the fracture toughness of Carbon Fibre Reinforced Polymer (CFRP)/metal joints, exploiting Additive Manufacturing (AM) to produce small features on the metal adherend. This first step is devoted to the qualification of the Mode I fracture toughness of the as-built AM surface. Thus, Double Cantilever Beam (DCB) tests are carried out on metal/metal secondary bonded and CFRP/metal co-bonded joints. The metal part is obtained by Selective Laser Melting (SLM) of AlSi10Mg aluminium alloy, without surface pre-treatment to preserve the as-built roughness. The fracture toughness of the AM un-treated joints is also compared to that of joints in which the metal adherend is sandblasted. Optical profilometry is employed to evaluate the surface morphology of both as printed and sandblasted adherends. The results show that the untreated joints have comparable fracture toughness to their treated counterparts, despite manifesting dissimilar failure modes due to the different surface morphologies.

Formation of primary intermetallic phases in the interaction of Fe-containing melts of recycled Al-Si alloys with Al2O3 and Al2O3-C filter materials: A µ-CT study

Fe is the most detrimental impurity element in recycled Al-Si alloys due to the formation of brittle, primary, Fe-containing, intermetallic particles during solidification. Their removal from the Al-Si melts e.g. by filtration can reduce the Fe content. New active filter materials can facilitate the formation of these particles for their removal and contribute to the production of high-quality, recycled Al-Si alloys. The interaction of the alloy with the filter material can lead to modification of the thermodynamics of the alloy or of the kinetics of the particle formation. Time-resolved, three-dimensional microstructural investigations have been carried out to study the formation of primary intermetallic particles in Al7.1Si1.5Fe and Al7.1Si0.75Fe0.75Mn alloy melts in contact with Al2O3 and Al2O3-C filter substrate material during a melt conditioning treatment at 620 °C. The microstructures, in particular the primary intermetallic particles αc and αh, have been characterized by computed tomography (CT) and supplementary scanning electron microscopy (SEM). As expected by thermodynamics, the total volume fraction of primary particles remains unchanged by the interaction with the substrate materials. However, kinetic advantages for Fe-removal efficiency can be achieved by an accelerated and preferred selective particle formation in contact with the Al2O3-C material. Furthermore, particle formation is discussed in view of its different stages: nucleation, growth, and ripening.

Fabrication of Aluminum Alloy with Open-Channel and Columnar Structures through a Ceramic Fiber Template Method

Aluminum alloys with open-channel and columnar structures were fabricated by casting the melt of aluminum alloys using a ceramic fiber template method. Stainless steel plates or wires coated with ceramic fibers impregnated by polyvinyl alcohol were used as cores. The cores were embedded in a melt of an aluminum alloy. After solidification, the ceramic fibers were macerated and became sodden by immersing the aluminum alloy ingots in water so that the plates or wires were easily removed by extraction forces as large as 5N, in other words, by pulling out them manually. Thus, an open-channel aluminum alloy was fabricated by a simple method. On the other hand, ceramic fiber blocks composed of ceramic fibers impregnated by polyvinyl alcohol were perforated by microdrills. Melts of aluminum alloy were cast in the holes by a vacuum suction method. The ceramic fibers were removed by immersing the ingots in water. Thus, a columnar-structured aluminum alloy was produced. Previous methods for the fabrication of open-channel metals necessitates a process to extract the metallic wires embedded in the solidified metals. However, the ceramic fiber template method does not require such an extraction process and thus is a very simple technique for the fabrication of open-channel metals, such as porous metals with rectangular holes and circular holes and columnar structures metals.

Development and Numerical Testing of a Model of Equiaxed Alloy Solidification Using a Phase Field Formulation

A computational framework is developed to understand the transient behavior of isothermal and non-isothermal transformation between liquid and solid phases in a binary alloy using a phase-field method. The non-isothermal condition was achieved by applying a thermal gradient along the computational domain. The bulk solid and liquid phases were treated as regular solutions, along with introducing an order parameter (phase field) as a function of space and time to describe the interfacial region between the two phases. An antitrapping flux term was integrated into the present phase-field model to mitigate the amount of solute trapping, which is characterized by the non-equilibrium partitioning of the solute. The governing equations for the phase field and the solute composition were solved by the cell-centered finite volume method using the open-source computational tool OpenFOAM. Simulations were carried out for the evolution of equiaxed dendrites inside an undercooled melt of a binary alloy, considering the effect of various computational parameters such as interface thickness, strength of crystal anisotropy, stochastic noise amplitude, and initial orientation. The simulated results show that the solidification morphology is sensitive to the magnitude of anisotropy as well as the amplitude of noise. A strong influence of interface thickness on the growth morphology and solute redistribution during solidification was observed. Incorporating antitrapping flux resulted in the solute partitioning close to the equilibrium value. Simulations show that the grain shape is unaffected by changes to crystallographic orientation with respect to the Cartesian computational grid. Thermal gradients exerted discernible effects on the solute distribution and the dendritic growth pattern. Starting with multiple nucleation events the model predicted realistic polycrystalline solidification and as-solidified microstructure.

High-value utilization of modified magnesium slag solid waste and its application as a low-carbon cement admixture

A large amount of magnesium slag solid waste, insufficient comprehensive disposal capacity, high disposal costs, and uncertain environmental stability hinder the low-carbon, green, and sustainable development of magnesium and magnesium alloy smelting. Therefore, this study proposed a high-quality, large-scale, and industrialized disposal method for modified magnesium slag (MMS). Through relevant experimental tests and microscopic characterization methods (physical and chemical performance, hydration heat, resistivity, and microstructure tests), the physical and chemical properties, curing mechanism, and social benefits of MMS low-grade magnesium slag were investigated. The physical and chemical properties, curing mechanism, and social benefits of modified magnesium slag low-carbon Portland cement (MMSPC) produced by MMS as a cement admixture were elucidated. The results showed that (1) the physical and chemical properties of MMSPC met the requirements of the GB 175–2007 “General Portland Cement” standard. (2) A significant difference was observed in the early hydration heat release of fresh MMSPC slurry, confirming a hydration composite effect between MMS and clinker, which was also the key reaction mechanism of MMS replacing clinker to produce MMSPC. (3) The resistivity of MMSPC increased, decreased, and then increased with time, which was mainly controlled by the settling of the aggregate, the dissolution of the binder, and the hydration reaction of the system. However, the variation in resistivity with time and value was influenced by the mixing ratio of the system. (4) MMSPC could also offer certain environmental and economic benefits. Carbon emissions per ton of cement produced were reduced by 7.95%, and the total cost per ton of cement produced was reduced by more than 10%. This study provided a theoretical basis for the high-value disposal of MMS and the reduction of carbon emissions in the cement industry.

The Effect of Vacuum Forming on the Quality of Refractory Materials

Various designs of furnaces for melting alloys are used in the foundry industry. Regardless of their design, they have one common detail, which is the lining of their interiors with refractory materials. This component in the design of a metal-melting furnace has a very important task—to protect the rest of the furnace assemblies from thermal and mechanical damage. Continuous technical progress and the quality requirements of casting production produce increasingly higher demands for refractory materials in connection with their development as well. The article presents the results of an innovative method of vibratory compaction of refractory material (high-alumina aluminosilicate) using reduced pressure. The analysis presents a comparative study of two methods used for forming refractory materials, i.e., the application of the mentioned innovative method and the classical (standard) method of compaction by vibration only. The effects of the introduced modification in the manufacture of ceramic shapes were evaluated by means of the material’s resistance to thermal shock, linear expansion, and dimensional change due to firing, apparent density, open porosity, and apparent specific gravity, determination of total pore volume and pore size distribution by mercury porosimetry, and slag resistance. The tests performed indicate that the procedure of lowering the pressure during the vibratory compaction of the refractory material creates a more homogeneous structure with a smaller number and size of pores. This makes it possible to improve most of the parameters that determine the quality of the refractories used for the linings of the foundry furnace.

Composite phase change material based on Al alloy with durability of over 10,000 cycles for high-temperature heat utilization

High-temperature latent heat storage (LHS) technology using alloy-based phase change materials (PCMs) is promising for high-temperature heat applications owing to its high heat storage capacity at a constant temperature. Microencapsulated PCMs (MEPCMs) coated with stable ceramics can help prevent corrosive reactions observed in alloy PCMs during heat storage. Because MEPCMs are considered as ceramic particles, a composite PCM can be prepared by compositing them with a sintering aid. In this study, composite PCMs consisting of MEPCM with Al–12 mass% Si alloy (melting point: 577 °C) particles with diameters of 31.7 or 68.2 μm, and α-Al2O3 as the sintering aid were prepared. The MEPCM used in the preparation of the composite PCM included alumina hydroxide and various alumina polymorphs as coatings. Pellet-like compacts were successfully produced by mixing each MEPCM with α-Al2O3. After heat treatment, the composite PCMs retained their shape. In particular, the latent heat capacities of the composite PCMs made from small and large MEPCMs with α-Al2O3 coatings were 171 and 231 J g−1, respectively. Moreover, the composite PCMs retained their shape and more than 80 % of their latent heat capacity after 10,000 and 1000 cycles. The developed composite PCMs, with their high latent heat capacity and durability, can be employed for high-temperature heat applications.

Development of Al/Mg bimetal prepared by ultrasonic vibration-assisted compound casting: Effects of interface treatment temperatures

In this work, the A356/AZ91D bimetals were fabricated by ultrasonic vibration-assisted solid-liquid compound lost foam casting. The ultrasonic vibration treatment (UVT) was introduced to the Al/Mg interfaces, and the effects of interface treatment temperatures on the formation, microstructures and mechanical properties of the Al/Mg interfaces were investigated. The results revealed that the Al/Mg interface without UVT was composed of intermetallic compounds area (Al3Mg2 + Al12Mg17 + gathered Mg2Si particles) and eutectic area (Al12Mg17 + δ-Mg). With UVT, phase compositions were not changed, but the distributions were got more homogeneous. The Mg2Si particles at the Al/Mg interfaces were refined and formed at eutectic area. Besides, the thickness of the Al/Mg interfaces were increased. When the UVT performed to the Al/Mg interface of above liquidus temperature of liquid Mg alloy melt, the solid insert was eroded by ultrasonic cavitation, cracks appeared between the Al/Mg interface and AZ91D matrix, which declined the shear strength of Al/Mg interface. When the UVT performed to the Al/Mg interface of temperature close to the formation temperature of it, the Al/Mg interfacial grains were refined and the Al–Mg eutectic structures were formed at intermetallic compounds area, which was not observed in the case of UVT performed to Al/Mg interface of elevated temperatures. The microhardness of the Al/Mg interfaces were increased and became more uniform by UVT, due to the refinement of Mg2Si particles and more homogeneous microstructure. The shear strengths of the Al/Mg bimetals with UVT were increased to 53.9 MPa from 35.5 MPa, with an increase of 51.8%. The fracture morphologies of the Al/Mg interfaces showed typical brittle fracture characteristics. However, the main cracks were hindered and deflected by dispersed Mg2Si particles and transformed to crack branches during deformation and thus enhanced the shear strengths of the Al/Mg bimetal.

Effects of laser power and printing speed on the temperature field during selective laser melting of aluminum alloy

Additive manufacturing (AM) has significantly transformed the manufacturing industry and found diverse applications. Selective laser melting (SLM), as a common and valuable rapid prototyping technology in AM, is also a very important technology. In SLM, temperature is a very important parameter, and parameters such as melting time and manufacturing speed are highly correlated with temperature. However, temperature is not easy to measure in real-time, and it is convenient to study the changes in temperature field through numerical simulation. This paper explores the quantitative impact of printing speed and laser power on the temperature field through simulation. The peak temperature decreases with increasing printing speed, but increases with increasing laser power. The high temperature affected area is mainly related to the printing speed and decreases as the printing speed increases. The relevant results can provide guidance and reference for the application of SLM engineering.

Desulfurization Behavior of FeNi-Based Expansion Alloy Melt Using CaO-SiO2-MgO-Al2O3-CaF2 Slag

The effects of slag components on the sulfur distribution ratio {(wt.%S)/[wt.%S]} were analyzed using thermodynamic calculations. On this basis, the effects of the slag with different binary basicities (wt.% CaO/wt.% SiO2 = 3.0, 5.0, 7.0, 9.0 and 11.0) and Al2O3 contents (wt.% Al2O3 = 12, 16, 20 and 24) on the desulfurization behavior were investigated. The results show that the binary basicity and Al2O3 content were the main factors that affected the desulfurization. And an increase in the binary basicity and a decrease in the content of Al2O3, increase the sulfide capacity of the slag. In the early stage of the smelting process, the desulfurization process was limited due to the high content of oxides, such as FeO and MnO in the slag, and the sulfur content in the alloy melt reached 35 ppm. After the final deoxidation of the Si-Ca alloy, the desulfurization rate was significantly increased, and the maximum desulfurization rate reached 44.12%. During the ladle standing, the sulfur content in the alloy melt changed little because of the limitation of kinetics. The rate-limiting step of the desulfurization process was the diffusion of sulfur in the alloy melt.

A Fully Implicit Enthalpy-Porosity Model for Phase-Change

Abstract This article proposes a new formulation for a phase change model based on the enthalpy-porosity idea. A general one-energy equation model (1EEM) is extended to deal with the melting and solidification of pure substances and alloys. Before melting and after solidification, solid material is seen as a porous media with low porosity and very small permeability. During phase change, thermal equilibrium in the mushy zone is assumed. Viscous and form drag in the volume-averaged momentum equation are reduced as the temperature rises above the melting point. In the energy equation, latent heat is treated implicitly in the accumulation term instead of explicitly as in most works in the literature. Liquid fraction for the entire field is updated after a new temperature field is calculated. Thermophysical properties are updated with the new liquid fraction field. Governing equations are discretized according to the control-volume method. Algebraic equation sets are relaxed with the Simple Method. Inner iterations make use of the Strong Implicit Procedure. Preliminary results indicate good agreement with the literature for pure substances.

Alternative Industrial Chrome-Free Alumina-Based Bricks for Copper Alloy Melting Furnaces

Abstract In this study, the corrosion resistance of alumina-based bricks against the slag of copper alloy melting furnaces was investigated. Four commercial chrome-free alumina bricks have been studied. Bulk density and apparent porosity measurements and phase analysis of the bricks were performed. The most important property, the slag corrosion resistance, was evaluated at the temperature of 1,200°C for 2 h. The microstructures of the bricks, their penetration depth, and corrosion index were evaluated. The results showed that two bricks showed acceptable corrosion resistance against the slag. The low corrosion index of these bricks was attributed to their aluminosilicate phases (sillimanite, or andalusite) and lower phosphate bonding; however, the problematic matter was the silicate phase, which showed lower resistance against the penetration of slag. It was observed that the aluminosilicate phase can improve the corrosion resistance through the reaction with slag, whereas the presence of large alumina aggregates can restrict the penetration of slag.

3D Chiral Energy-Absorbing Structures with a High Deformation Recovery Ratio Fabricated via Selective Laser Melting of the NiTi Alloy.

Excellent energy-absorbing structures have been highly sought after in engineering applications to improve devices and personal safety. The ideal energy absorption mechanism should exhibit characteristics such as lightweight, high energy absorption capacity, and efficient reusability. To address this demand, a novel three-dimensional (3D) chiral lattice structure with compression-twist coupling deformation is fabricated by combining the left and right chiral units. The proposed structure was fabricated in NiTi shape memory alloys (SMAs) by using laser powder bed fusion technology. The compression experiment result indicates that the shape recovery ratio is as high as 94% even when the compression strain is over 80%. Additionally, the platform strain reaches as high as 66%, offering high-level specific energy absorption, i.e., 213.02 J/g. The obtained results are of great significance for basic research and engineering applications of energy-absorbing structures with high deformation recovery ratios.

Finite element heat transfer analysis in selective laser melting of AlSi10Mg alloy using bi-directional scan strategy: Enhanced thermal conductivity considerations

In the present work, a 3D finite element model was created using the commercial ABAQUS software to analyze the selective laser melting process of AlSi10Mg powder in a bidirectional multi-track, multi-layer configuration. The focus of this investigation was to examine distribution of temperature, melt pool geometry, thermal history, and the temperature change rate. To improve the accuracy of the results, the enhanced thermal conductivity was utilized to incorporate the Marangoni convection effect. The results revealed that, in the initial track, the maximum temperature and dimensions of the melt pool increased, ultimately reaching a plateau as the deposited path extended. However, using a bidirectional scan strategy, the maximum temperature at the second track reached its peak and then stabilized. While the maximum heating and cooling rates in the first track showed a nearly identical trend, both parameters decreased at the beginning of the second track and then began to rise again. It can be attributed to the overlapping of the molten zone between the first and second tracks. With an increase in the number of tracks, the maximum temperature, melt pool width, and depth increased until they reached a steady state, with specific values of 2093 K, 258 μm, and 150 μm, respectively. Introducing more layers initially caused an increase in the maximum temperature and dimensions of the melt pool, which eventually reached a steady-state condition. Finally, temperature distribution of the steady-state simulated melt pool was found to match with thermal behavior and eutectic Si features of the experimental sample.

Review on the preparation methods and strengthening mechanisms of medium-entropy alloys with CoCrNi as the main focus

Medium-Entropy Alloy (MEA) is a new metal material with high strength, high hardness, high corrosion resistance and excellent high temperature properties. With its excellent performance makes it promising for a wide range of applications in the fields of aerospace, automotive, energy and biomedicine. In addition, the continuous breakthroughs in preparation process have promoted the development of MEA with unique appeal. So far, outstanding results have been achieved in the preparation technology of MEA, and the scientific field of improving the performance of MEA by adjusting the process technology has received much attention. No work has been reported specifically on MEA preparation methods and enhancement mechanisms, and a review is needed to summarize the current state of research in this area. In this paper, we review the research progress of MEA in both preparation process and strengthening mechanism, and introduce in detail the arc melting, induction melting and mechanical alloying and deposition methods with CoCrNi as the main focus, and analyze the advantages and disadvantages. Finally, the prospects and challenges for the development of optimally designed MEA are presented.