Aluminum Melt Research Articles

PENGECORAN ALUMINIUM MATRIKS KOMPOSIT BERPENGUAT CARBON NANOTUBE (CNT) DENGAN VARIASI PENAMBAHAN SERBUK MAGNESIUM

Aluminum matrix composite reinforced CNT have been developed to improve the mechanical properties of aluminum. In this study, the melting of Aluminum 1100 reinforced Carbon Nanotube (1 wt.% CNT) with variations in the addition of Magnesium powder was carried out by the slurry-based method. The casting of the specimens is carried out using a metal mold. CNT powder was first mixed with magnesium powder at 60°C. Then the aluminum is melted to a temperature of 700°C until it melts, then the temperature is lowered to 500°C or the texture has changed to be like mush (slurry based) and then mixed with CNT powder and Magnesium powder are added. After that the alloy was raised again at 720°C for 30 minutes and the stirring process was carried out, after that it was poured into a metal mold with a mold temperature of around 400°C. The samples were then analyzed for mechanical properties and microstructure observations. The results of the Vickers hardness test before the addition of Mg powder and CNT were 36.7 HV. While after the variation of adding 1wt.% Mg powder, the hardness of the specimen increased to 44.5 HV, the variation of adding 3% Mg powder was 45.3 HV, and the variation of adding 5% Mg powder reached a hardness value of 46 HV. The tensile test results on 3% Mg powder is 241.6 MPa. The wear test results show the wear rate value for the 1% Mg variation of 0.146 mg/s, the 3% Mg variation of 0.106 mg/s, and the 5% Mg variation with a wear rate value of 0.093 mg/s. The α-Al phase is the dominant phase formed, where the grain size and grain boundaries in the 3% Mg variation have a relatively small size and the spread of CNT is evenly distributed in the alloy, so the addition of Mg to the alloy can help spread CNT in Aluminum alloys.

Вивчення взаємодії інфрачервонопрозорих матеріалів ZnSe, ZnS, Si, Ge з розплавами металів

Wetting of infrared-transparent materials — selenide and sulfide zinc, germanium, and silicon by metal melts in a vacuum in a wide temperature range was studied by the sessile drop method using the method of capillary purification of the drop melt during the experiment. Pure metals In, Sn, Pb, Al, Fe, Ni, binary Al—Si, Ge—Si, In—Cu and multicomponent In—Sn—Cu—Ti alloys were used. When zinc chalcogenides are wetted with In—Sn—Cu—Ti melts, zinc selenide is wetted better than zinc sulfide. This is due to the lower thermodynamic stability of selenide. In systems where copper is present in melts, wetting is affected not only by the interaction of selenium or sulfur with titanium, but also by the interaction of copper and zinc (in the copper-zinc system, solid solutions of copper and zinc are formed and copper dissolves in solid zinc). This conclusion also confirms the wetting of the substrate by the In—Cu melt. The values of the contact angle at 650 C are equal to 32, which is less than for the In—Sn—Ti melt at the same temperature. It can be said that for such a system, the interaction of zinc with copper is very important, which is not inferior to the wetting effect of the interaction of chalcogens with titanium. The wetting of single crystals of germanium and silicon by metal melts improves with increasing temperature. Iron and nickel wet silicon (contact angles close to zero) at temperatures lower than their melting point. Contact melting also occurs when silicon substrates are wetted with aluminum melts (the eutectic in the Al—Si system has a temperature of 577 °C). Germanium is better wetted by tin than by indium and lead. Technological processes of soldering infrared transparent materials with metals were developed and soldered joints were obtained. Keywords: infrared transparent materials, polycrystalline zinc selenide and sulfide, single crystals of germanium and silicon, wetting, soldering.

PIXE analysis of contaminants in tree rings in proximity of the aluminum processing factory in Ladomerská Vieska (Slovakia)

The aluminum smelter in the Žiar nad Hronom region of central Slovakia was a substantial source of pollution in the past. Five trees were sampled in close proximity to the smelter and the tree rings were chemically processed and analyzed with the PIXE technique. Elevated concentrations of Mg, Al, Si, P, S, K, Ca, Fe, and Zn were observed in tree rings, however, they did not show a significant correlation with PM, HF and SO2 emission rates. Concentration trends show a significant effect of the heartwood-sapwood boundary layer, where a substantial drop or increase was observed between tree-ring sections.

Cooling rate calculation of pure aluminum solidified during a novel gas-assisted continuous casting and extrusion process

Gas-assisted continuous casting and extrusion (GAC) process is a novel technique for the continuous preparation of non-equilibrium solidified materials. To evaluate the solidification rate of the melt during GAC, the cooling rate of pure aluminum melt solidified in the wheel groove is calculated, based on the Newtonian heat transfer model and the one-dimensional Fourier heat transfer model. Results show that the cooling rate of the melt during GAC mainly depends on the conduction heat transfer in the wheel groove and the melt thickness. When the thickness of the pure aluminum melt is between 1 and 2.5 mm, the cooling rate can reach 103–104 K s−1, which is much higher than that in CAXTEX (~10 K s−1). It means that GAC is a very effective process in the preparation of non-equilibrium solidification alloys.

Improving the Energy Efficiency of Aluminum Smelting Using the Anode Preheating Technology

Improving the Energy Efficiency of Aluminum Smelting Using the Anode Preheating Technology

Corrosion Resistance of Fe-Cr-Al Intermetallic Coatings Obtained by Aluminizing

The growing interest in intermetallic and metal–intermetallic materials and coatings is based on the number of favorable properties they possess, primarily mechanical. However, the lack of data on their corrosion resistance has largely limited their scope of application. In this study, the corrosion destruction mechanisms of coatings formed on substrates made of AISI 321 steel and Aluchrom W (fechralloy) were investigated. The coatings were created by alloying in an aluminum melt followed by diffusion annealing to form the ultimate intermetallic structure. Corrosion resistance was studied under cyclic exposure to a humid marine atmosphere simulator and potentiostatic tests in an aqueous NaCl solution. Corrosion destruction parameters were determined, and mechanisms for each type of coating were revealed. The conducted studies allowed us to determine the electrochemical parameters of the corrosion destruction process and its mechanisms. It was shown that the corrosion rates during potentiostating for coatings on substrates Cr15Al5 and 12Cr18Ni10Ti differed by almost twofold. Two different mechanisms of corrosion are proposed. The first is associated with the formation of Al2O3 and MgO oxide films, which at the initial stage protect only local areas of the coating surface on Cr15Al5. The second is determined by the diffusion of titanium atoms during annealing to the coating surface on a 12Cr18Ni10Ti steel substrate with the formation of TiC carbide at the grain boundaries.

INVESTIGATION OF CARBON-ALUMINUM COMPOSITE WITH A BARRIER COATING ON CARBON FIBERS

Barrier SiO2 coatings on the surface of carbon fibers were deposited by the sol-gel solutions (dip coating) based on tertraethoxysilane Si(C2H5O)4. The average thickness of the barrier SiO2 coating on carbon fibers is 127 ± 30 nm. Carbon-aluminum composites were obtained by a type of liquid-phase infiltration — by the shell molding process. The components of the composite were placed in a steel hermetic shell, then after the shell evacuate and heat until the aluminum melts, the fibers were infiltrated by the melt under the external pressure, followed by cooling. Composites with SiO2 coating and without coating on carbon fibers were obtained. After extracting the composite from the metal shell, the structure, phase composition, and mechanical properties of the samples were studied. Studies of the structure of composites showed that the interfiber space is filled with aluminum melt, without porosity and macroscopic defects. The study of the phase composition of the composite reinforced with uncoated carbon fibers showed that aluminum carbide peaks are observed at the angles 2θ = 41°, 67°, 74°. Quantitative analysis carried out by the Rietveld method revealed that the amount of aluminum carbide in the composite is 12.0 ± 1.3 %. The deposition of a barrier SiO2 coating on carbon fibers leads to a decrease in the intensity of the main peaks of aluminum carbide, while the amount of Al4C3 decreases by 4 times, to 3.0 %. An analysis of the fracture surface of the samples after mechanical testing revealed that the fracture of the composite reinforced with uncoated carbon fibers is almost flat. No protrusions and relief are observed on the fracture surface. The fracture surface of a composite reinforced with coated carbon fibers has a relief surface, and separately sticking out fibers are observed. Mechanical tests of samples for three-point bending showed that the barrier coating on the fibers increases the strength to 520 ± 50 MPa, the strength of the uncoated composite is 350 ± 8 MPa. Barrier SiO2 coating applied to the surface of carbon fibers prevents the formation of aluminum carbide and fiber degradation in the carbon-aluminum composite.

Vapor-Phase Contribution to Laser-Induced Plasma Emission of Magnesium in Liquid Aluminum.

Liquid aluminum containing the important alloying element magnesium in varying concentrations was analyzed using in-situ laser-induced breakdown spectroscopy (LIBS). Magnesium emission shows an exponential dependence on melt temperature that correlates well with the expected partial pressure of magnesium above the aluminum melt. Furthermore, comparison with LIBS measurements on corresponding solid samples supports the conclusion that a significant part of Mg emission from liquid metal samples originates from the vapor phase above the metal surface. Simultaneously, curves of growth measured over four orders of magnitude in Mg concentration reveal a level of self-absorption for liquid aluminum samples that is stronger than for solid aluminum samples having a corresponding Mg concentration, and beyond what is expected from conventional plasma models. The implications for measurements of volatile species in liquid metals in general are discussed.

Binder Content and Storing Conditions of Inorganically-Bound Foundry Cores Determine the Intensity and Onset Time of Gas Release in Metal Casting

Organically-bound foundry cores are substituted by inorganically-bound cores increasingly. This trend is due to regulatory efforts, workplace safety issues, and increasing costs for waste deposits. Changing the binder system reduces the emissions to mostly water vapor, solving health and safety issues. Yet, the difference in the behavior of the gas phase, namely, the condensation potential of water, changes the casting process drastically. In contrast with the continuous generation and discharge of combustion products in the case of organic binders, water accumulates within the foundry core. Only once the cold spots of the core reach boiling temperature noteworthy amounts of vapor are created, increasing the chance for gas defects of the cast parts. Countermeasures have to be taken when designing the core’s geometry. We conducted the following research to improve the understanding of core gas release and its interactions with the foundry core’s binder content and storage conditions. Both binder content and relative humidity during storage were varied in three steps. Their influence on the core gas amount, time of gas generation, and gas permeability of the cores were investigated. The experiments were performed in the institute’s Induction Analysis Furnace and an aluminum melt bath. We found a strong dependency of storage humidity, further increased by increasing binder content on the gas amount and time of the gas release.

Nucleation Work on Curved Substrates

Nucleation is the initial phase transition process when nuclei of a new phase form within an undercooled or supersaturated parent phase under appropriate conditions. Nucleation most often occurs through a heterogeneous process on active centers on which the probability of nucleus formation is high. In general, the origin of active centers may be difficult to distinguish. In this work, we consider the formation of crystalline nuclei in a melt on various curved substrates. Knowledge of excess free energy plays a key role in understanding the process of formation of clusters and it is not easy to express this quantity in a considered system. Excess free energy is often approximated within the framework of capillarity approximation based on interfacial energy, which depends on interatomic interactions near the interface, as well as the misfit between melts, surface roughness, temperature, composition, etc., near the phase interface. The formation of nuclei requires overcoming a certain energy (nucleation) barrier that is a consequence of balancing the volume and the interfacial free energy. Knowing the nucleation barrier (W) is crucial for understanding this process, as nuclei predetermine the physical properties of a newly formed phase. W is typically expressed as a function of the nucleus radius; however, in nucleation kinetics, one needs to determine (W) as a function of the number of molecules forming the nucleus. We analyze nucleation work on various substrates (flat, convex, and concave) for crystallization from an aluminum melt to show that the formation of nuclei is the most probable on concave substrates. An analytical expression for W can be easily applied to other systems under consideration. We show that under the same conditions, the critical radius of nuclei is identical for various substrate, in contrast with the critical number of molecules forming a nucleus.

Interaction kinetics between molten aluminium alloy Al99.7 and H11 tool steel with and without an AlCrN protective coating

The tool used in die casting or hot forming is subjected to thermal and mechanical stress, resulting in damage and cracking due to thermal fatigue and melt flow. This reduces the profitability and efficiency of production, as the products may not meet the required dimensions and mechanical properties. Understanding the interaction between tool steel and molten aluminium alloy is critical to extending tool life. AlCrN protective coatings on tool surfaces can improve corrosion resistance, thermal fatigue and wear resistance.The present work was carried out to predict the effect of the AlCrN protective coating on the interaction kinetics between H11 tool steel and molten aluminium alloy Al99.7. The AlCrN protective coating on the H11 tool steel sample served its purpose and slowed down the interaction between the aluminium melt from Al99.7 and the H11 tool steel, as the DSC curve of the sample that had the AlCrN protective coating applied flattened out faster, indicating the cessation of dissolution in the material at all investigated temperatures. Measurements of the thicknesses of the interaction layers also confirmed these results, whereas the thickness of the composite layer was almost the same at both experimental temperatures, 670 °C and 700 °C, respectively, without an AlCrN protective coating; the temperature has no effect on this layer and the types of interaction layers did not differ from each other.

IMPROVING THE STRENGTH AND CORROSION PROPERTIES OF ALUMINIUM ALLOYS WHEN MODIFICATION WITH NANODISPERSED COMPOSITIONS

Aluminium alloys of the Al-Si and Al-Mg-Sc systems, which are promising for nuclear power generating facilities, were studied. The AK9 aluminium casting alloy and the 1545 wrought alloy were selected as the study materials. Modification of aluminium alloys with a multicomponent nanodispersed modifier based on Mg2Si and SiC was proposed. Grain grinding of modifying alloys by 1.5–2 times, strength properties increasing by 12…18% and corrosion resistance improving were achieved. The mechanism of action of the multicomponent nanodispersed modifier in an aluminium melt was proposed. The use of such modifiers facilitates the technological process, is environmentally safe, and leads to a uniform distribution of the introduced nanocompositions, which increases the strength and stability of alloys. The results achieved showed the effectiveness of modification aluminium alloys with nanodispersed compositions.

Phase analysis of complex non-metallic inclusions in Al-deoxidized 42CrMo4 steel after contact with MgO–C refractories

This study extensively investigated characteristic non-metallic inclusions in oxidized and deoxidized 42CrMo4 steel after contact to MgO–C refractories, proposing possible formation and modification mechanisms of non-metallic inclusions. The structures and compositions of different inclusion species were analyzed, revealing various types: crystalline, amorphous, and complex inclusions containing both crystalline and amorphous phases. The latter always consisted of an amorphous Mn–Si–Al–O matrix containing various crystalline phases such as Al2O3, MnAl2O4 and/or MnTiO3. The formation of amorphous Mn–Si–Al–O inclusions was attributed to steel melt oxidation, while pure crystalline corundum inclusions resulted from both the steel melt oxidation and deoxidation. Alumina inclusions exhibited different shapes, likely because of variations in aluminum and oxygen supersaturation in the steel melt during their formation. Complex inclusions were suggested to form through precipitation on existing inclusions and mutual collision of pre-existing inclusions, facilitated by the non-wetting behavior of solid alumina inclusions in the steel melt.

Influence of High-Pressure Die Casting Process Parameters on the Compound Strength of Hybrid Components with Undercut Sheet Metal

Reducing the weight of parts through lightweight designs impacts CO2 emissions, especially in the automotive and transportation sectors, which have significant fuel and electric energy consumption. Using multi-material design approaches, specific material properties can be combined to achieve effective lightweighting. Commonly used metals include aluminum, which is known for its high specific strength, and steel, which is valued for its strength and structural integrity. However, joining aluminum and steel presents challenges given their different thermophysical properties and the potential formation of brittle intermetallic phases, making common joining techniques like fusion welding unsuitable. In this study, a hybrid casting process for the production of a complex workpiece from dissimilar materials was investigated. Aluminum was die-cast around a steel sheet insert. Surface structures with undercuts on the steel sheet were applied through modified cold rolling, allowing molten aluminum to flow into the channels and interlock during solidification. It was found that elevated temperatures of the melt and tool were beneficial for the interlocking, resulting in a 30% increase in compound strength. Furthermore, a reduction in both the piston position at the changeover point, between the pre-filling and cavity filling, and the melt velocity at the gate reduced the compound’s strength by 41% and 30%. Up- and downstream processes did not show any significant influence on the conducted experiments. Based on this, two main detrimental effects were observed: pre-solidification of the aluminum melt and gas entrapment.

Sustainable recycling of aerospace-grade ultra-clean 7050 aluminum alloy melts through argon refining without secondary aluminum dross generation

The refining of aluminum scraps commonly employs nitrogen-fluxes to eliminate impurities. However, the aluminum nitride (AlN) generated by the reaction between nitrogen and the aluminum melt, along with residual fluxes, contribute to low cleanliness of the recycled aluminum melt and pose difficulties for the disposal of secondary aluminum dross (SAD). Our innovative research has resulted in the recycling of aerospace-grade clean aluminum alloy melts. The results indicate that the argon bubble floating process adsorbs inclusions and hydrogen, achieving an aerospace-grade ultra-clean melt. The solid-liquid interface between the tube wall and the melt provides a diffusion channel for hydrogen atoms, and the bubbles rising up along the wall lead to a higher hydrogen content in the melt. The argon refining dross is primarily composed of Al and Al2O3, which can be recycled as a raw material for aluminum electrolysis. Argon refining can decrease the hydrogen content and the number of inclusions with particle size ≥40 μm in the recycled aluminum melt to the level of aerospace aluminum alloy melt. Nonetheless, the particle size ≥20 μm remains 1.5–2.5 times that of primary aluminum.

Temperature effects of aluminum melt during the infiltration process into porous graphite matrix

Aluminum/graphite composites are receiving much attention due to the unique features and diverse possibilities in different fields. Generally, the aluminum melt into the inner pores of the graphite matrix requires an ambient prompting with high temperature and gas pressure. The infiltration dynamics of aluminum melt, which highly depends on the ambient temperature, would have a significant effect on the final composite’s performance. In this work, we have studied the temperature effect of aluminum melt during the infiltration process into the porous graphite matrix based on numerical simulation and experimental verification. Results show that the moderate temperature increase would effectively promote the infiltration of aluminum melt, achieving a higher filling rate with a shorter filling time. However, the promotion effects of the temperature increase would come to a certain limit due to the opposing effects of capillary porous and residual gas. The detailed influences of the temperature on the infiltration would be presented, and the final composite performance, including mechanical strength and thermal management capability, would be examined and discussed.

Study on chemical corrosion properties of titanium alloy in 2A14 aluminum melt

Titanium alloy radiation rods have excellent physical and chemical properties compared to other materials, and are commonly used for ultrasonic casting of 2A14 aluminum alloy. However, titanium alloys are chemically corroded in high-temperature aluminum melts for a long time, making it difficult to precisely regulate the elemental composition during casting. In order to better understand the high-temperature chemical corrosion mechanism of titanium alloy radiation rods, this research looks into the corrosion morphology, weight loss, surface roughness, and reaction layer. The study’s findings suggest that the rate of chemical corrosion of titanium alloy in high-temperature aluminum melt is often inversely correlated with the degree of roughness, with the degree of roughness changing nonlinearly during the corrosion process. Titanium alloy weight loss rates with roughness Ra0.4 μm, Ra7.2 μm, Ra9.5 μm and Ra9.8 μm are 0.16 mg per min, 0.25 mg per min, 0.37 mg per min and 0.29 mg per min, respectively. The corrosion product of the chemical corrosion process is TiAl3, which is granular. Under varying roughness conditions, the solid-liquid interface of Al/Ti emerges reactants after 4 min, and the TiAl3 reaction layer arises after 12 min. Furthermore, the reaction layer with little roughness is flat and compact, whereas the reaction layer with great roughness is loose and contains many faults. At the same time, the growth rate of the reaction layer decreases slightly. And the greater the surface roughness, the greater the TiAl3 reaction layer grows at the titanium alloy matrix.

Determination of Optimal Modifier Level for Eutectic Silicon Phase in Hypoeutectic AlSi7Mg0.3Cu0.5 Cast Alloy

Silicon particles in as-cast aluminum alloys can be modified using various modifiers, with Strontium (Sr) and Sodium (Na) being the most employed in the aluminum casting sector. However, their concentration diminishes (fades) during the melting furnace process. Modifier fading within the melt can result from three principal chemical reactions: vaporization of the modifier under high vapor pressure conditions at melting temperatures, oxidation driven by a significant affinity for oxygen, or interaction with other elements in the melt leading to the formation of intermetallic compounds. Given the very low vapor pressure of both Na and Sr, their vaporization from the aluminum melt was excluded as a reason for the modifier's fading. Oxidation seems to be like the primary chemical reaction leading to the fading of Na and Sr from the aluminum melt. This study examined the effect of Sr and Na fading on the modification level of silicon particles in the AlSi7Mg0.3Cu0.5 (356) aluminum alloy. The cooling curve analysis has been utilized to quantify modifier fading. Approximately 105 ppm of Sr in the form of master alloy (AlSr10) and 67 ppm of Na in the tablet form were separately added to the melt. Both modifiers were kept in the melt for approximately 200 minutes to monitor their fading. The present paper aimed to quantify the fading of Na and Sr in an AlSi7Mg0.3Cu0.5 alloy. The depletion of modifiers (Na and Sr) while the melt is retained in a furnace can be quantitatively determined through equations derived from existing literature. The surface reaction rate constant (ks), once calculated, serves as a tool for predicting the extent of modifier loss during the melt-holding process in both industrial and laboratory furnaces.

Steel, Aluminum, and FRP-Composites: The Race to Zero Carbon Emissions

As various regions around the world implement carbon taxes, we assert that the competitiveness of steel products in the marketplace will shift according to individual manufacturers’ ability to reduce CO2 emissions as measured by cradle-to-gate Life Cycle Analysis (LCA). This study was performed by using LCA and cost estimate research to compare the CO2 emissions and the additional cost applied to the production of various decarbonized materials used in sheet for automotive industry applications using the bending stiffness-based weight reduction factor. The pre-pandemic year 2019 was used as a baseline for cost estimates. This paper discusses the future cost scenarios based on carbon taxes and hydrogen cost. The pathways to decarbonize steel and alternative materials such as aluminum and reinforced polymer composites were evaluated. Normalized global warming potential (nGWP) estimates were calculated assuming inputs from the current USA electricity grid, and a hypothetical renewables-based grid. For a current electricity grid mix in the US (with 61% fossil fuels, 19% nuclear, 20% renewables), the lowest nGWP was found to be secondary aluminum and 100% recycled scrap melting of steel. This is followed by the natural gas Direct Reduced Iron–Electric Arc Furnace (DRI-EAF) route with carbon capture and the Blast Furnace-Basic Oxygen Furnace (BF-BOF) route with carbon capture. From the cost point of view, the current cheapest decarbonized production route is natural gas DRI-EAF with Carbon Capture and Storage (CCS). For a renewable electricity grid (50% solar photovoltaic and 50% wind), the lowest GWP was found to be 100% recycled scrap melting of steel and secondary aluminum. This is followed by the hydrogen-based DRI-EAF route and natural gas DRI-EAF with carbon capture. The results indicate that, when applying technologies available today, decarbonized steel will remain competitive, at least in the context of automotive sheet selection compared to aluminum and composites.

Incorporation of polysilazane precursor into aluminium melt for in-situ pyrolysis: Synthesis of in-situ metal matrix composites

This manuscript describes a polymer precursor approach to synthesize polymer derived SiCN ceramic dispersed in aluminum metal. The composites were prepared by in-situ pyrolysis of cross-linked polysilazane powder within molten aluminum metal at 800 °C by stir-casting method. The castings were hot extruded, vacuum arc remelted (VAR), and suction cast into copper mold. Microstructure analysis revealed the presence of Si- needles in addition to reinforced particles. The microstructure was dendritic and consisted of a uniform dispersion of SiCN phase within columnar grains, with some segregation to grain boundaries. The VAR process significantly improved the hardness, yield strength and ductility of these composites.