Al-Si Materials Research Articles

Coral-shaped AlSi anode materials for Li-ion batteries enabled by THF-based electrolyte

This research aims to implement a strategy of using a controlled acidic etching on AlSi alloy particles to partially remove Al and preserve a porous Si framework as anode materials. The etched AlSi materials with different Al/Si weight ratios have been investigated in lithium-ion batteries. Microstructural analysis shows the evolution of the AlSi material during selective wet etching, highlighting the preservation of coral-shaped Si nanostructures with an Al-rich core. Lower Al/Si ratios result in increased surface area and pore volume, which is favorable for improving lithium-ion diffusion and accommodating volume expansion during cycling. Evaluation of electrochemical performance in different electrolytes proves the importance of electrolyte selection for AlSi anodes. The tetrahydrofuran-based (THF-based) electrolyte stabilizes electrochemical reactions, resulting in superior specific capacity, cycle life, and Coulombic efficiency compared to the carbonate-based electrolyte with fluoroethylene carbonate additive. Rate performance analysis shows excellent high-rate capability with stable capacity retention at 3C, particularly in Al53Si47 and Al10Si90 materials. Electrochemical impedance spectroscopy measurements emphasize the critical role of porous structure and electrolytes in sustaining low resistance and enhancing cycle life performance. Selective aluminum etching and the THF-based electrolyte effectively mitigate the breakdown and subsequent reformation of the solid electrolyte interphase, resulting in superior efficiency and extended lifespan.

Influence of manganese content on the microstructure and properties of AlSi10MnMg(Fe) alloy for die castings

This paper was to determine the effect of different manganese addition contents from 0.2 to 1.0 wt.% on the microstructure, HB hardness and selected mechanical properties (UTS; YS; EL) of AlSi10MnMg alloy with increased iron content (about 1.0 wt.%). The proportion of iron in the studied alloy is so high because approx. 50% of the charge came from secondary materials.Chemical composition tests were performed using a Foundry Master Compact 8 emission spectrometer. Static tensile testing at ambient temperature was carried out according to PN-EN ISO 6892-1 on an Instron 3382 using a 20:1 ratio and a constant tensile speed of 5 mm/min-1. Tensile strength (UTS), conventional yield strength (YS), and per cent elongation after rupture of a proportional sample (EL) were determined from this test. Brinell hardness measurement was performed on a Zwick ZHF1, with a loading force of 250 N, with a 5 mm diameter ball for 35 s. Ten measurements were taken, discarding the two outliers, and the arithmetic mean was calculated from the remaining measurements. Metallographic studies were conducted on a MeF-2 Reichert light microscope. X-ray microanalysis studies were carried out on a Hitachi S-3400 scanning microscope coupled to an EDS Voyager X-ray spectrometer equipped with an SE secondary and BSE backscattered electron detector. Chemical composition analysis was performed by energy dispersive X-ray microanalysis (EDS) using a Thermo Noran detector.Increased iron content in aluminium-silicon alloys is a major concern. It causes a significant reduction in the mechanical properties of the materials. This is due, among other things, to the increasing scarcity of primary materials (high cost and environmentally unjustifiable) versus the increasing share of recycled materials. Based on the study, AlSi10MnMg(Fe) alloys obtained under pressure with higher iron content (about 1% wt.), the optimal value of manganese addition is about 0.58% wt.This research has shown that it is possible to use recycled Al-Si materials. The article presents one way to reduce the negative impact of iron addition to aluminium alloys as a result of reusing this type of material.The article presents the effect of manganese addition on the selected aluminium alloy. It was determined that the addition of manganese in the amount of 0.58% wt. causes a significant reduction in the negative effect of iron phases. The article is intended not only for the academic community but also for specialists in the foundry industry.

Microstructure and Mechanical Properties of Al-Si Alloys Produced by Rapid Solidification and Hot Extrusion.

The paper presents the results of tests of rapid solidification (RS) aluminum alloys with the addition of silicon (5%, 11%, and 20%). Casting by melt-spinning on the surface of an intensively cooled copper cylinder allowed to obtain a metallic material in the form of flakes, which were then consolidated in the process of pressing and direct extrusion. The effect of refinement on structural components after rapid solidification was determined. Rapidly solidified AlSi materials are characterized by a comparable size of Si particles, regardless of the silicon content, and the shape of these particles is close to spheroidal. Not only Si particles are fragmented, but also the Al-Si-Fe phase, which also changed its shape from irregular with sharp edges to regular and spherical. The melt-spinning process resulted in a fine-grained structure compared to materials obtained by gravity-casting and extrusion. The influence of the high-temperature compression test on the mechanical properties of rapidly solidified materials was analyzed, and the results were compared with those of gravity-cast materials. An increase in strength properties was found in the case of the AlSi5 RS alloy by 20%, in the case of AlSi11RS by 25%, and in the case of the alloy containing 20% Si by as much as 86% (tensile test). On the basis of the homogeneity of the particle distribution determined by the SEM method, it was found that rapid solidification is an effective method of increasing the strength properties and improving the plastic properties of Al-Si alloys.

Investigation of residual stresses and microstructure effects on the fatigue behaviour of a L-PBF AlSi10Mg alloy

Al-Si alloys produced by Laser Powder Bed Fusion (L-PBF) techniques allow the fabrication of lightweight free-shape components that find space in aerospace, automotive, biomedical and military applications. Due to the high cooling rates occurring during the building process, L-PBF AlSi10Mg alloys exhibit an ultra-fine microstructure that leads to superior mechanical properties in the as-built condition compared to conventional cast Al-Si materials. Nevertheless, L-PBF processing induces high thermal gradients, leading to deleterious residual stress levels that must be considered to avoid part distortion and unpredicted failures. In order to relax detrimental residual stress and to increase the ductility, post-processing stress relief treatments are generally performed. In as-built condition the hypoeutectic AlSi10Mg microstructure consist of fine α-Al cells containing uniformly dispersed silicon nanoparticles, which are, in addition, surrounded by a eutectic Si network. Above 260°C the silicon interconnectivity starts to breakdown into spheroidized particles and to coarsen. At the same time, the heating residual stresses are relieved.The objective of the contribution is to investigate, under different heat treatment conditions, the evolution of microstructure and residual stresses in view of optimizing the fatigue performance of the alloy. To this purpose various heat treatments in a range of temperatures between 265°C and 300°C for a duration between 15 minutes and 2 hours are performed. The microstructure modifications are analysed using a scanning electron microscope and the residual stress state is measured by laboratory X-ray diffraction.

The red deer antler: Bioinspired design of an Al[sbnd]Si composite with a fenestrated network-particle structure

Conventional AlSi materials always have a coarse and discontinuous Si structure, which limits their application as thermal management materials. Fortunately, nature has evolved efficient strategies to form complex microstructures that exhibit excellent wear resistance and thermal properties; one such example is found in the red deer antler. Here, inspired by the antler structure, AlSi composites with a novel fenestrated network-particle structure (FN) and with a common isolated island structure (II) are designed and prepared. Subsequently, the dynamic formation of FN is tracked and studied using computational fluid dynamics (CFD) simulation. To investigate the reinforcement mechanisms of FN, the wear resistances and thermal properties of FN and II are compared and analyzed. Simulation and experimental results show that the reconstruction of a semi-continuous structure promotes the formation of a striated structure, whereas flowing Si particles provide some sites for the formation of the fenestrated structure. The dynamic formation of FN is strongly influenced by the convection–diffusion process and the flow path. Moreover, this biomimetic FN structure exhibits better wear resistance and thermal properties than II, owing to its strong structural support and high expansion resistance. This work is expected to provide new perspectives on the microstructural design of thermal management materials with good wear resistance.

Tribological investigations with near eutectic AlSi alloys found in engine vane pumps – Characterization of the material tribo-functionalities

This paper gives attention to wear and friction processes of sliding contacts with cover parts of variable displacement engine vane pumps. Two near eutectic aluminium-silicon alloys for different casting processes were characterized by tribological investigations. This was done with the aid of specifically designed test methods on model scale as well as by damage analysis of real life parts from engine tests. The latter was additionally used as a validation measure for the model tests, which proved transferability of damage events from model tests to the engine parts. The results emphasize significance of the material structure of near eutectic AlSi materials on the wear performance. A pronounced load bearing structure of eutectic Si is able to provide high wear resistance.

In-situ formed, ultrafine Al-Si composite materials: ductility

Purpose: The work objective includes optimization of the casting production and heat treatment processes that will simultaneously maximize the combination of strength, hardness, and ductility for hypereutectic Al-Si compositions with Si volume fractions of as much as 25 vol.%. In addition, such an in-situ formed composite alloy will attain a unique combination of low production cost, high potential recycled content, and functional characteristics suitable for mission critical aerospace and vehicular applications. Design/methodology/approach: The unique High Pressure Die Casting Universal Metallurgical Simulator and Analyser (HPDC UMSA) was used for melting, cyclic melt treatment, and solidification of the hypereutectic Al-Si-X (A390). The produced as-cast structures contained colonies of nano-diameter Si whiskers and other morphologies, and absence of primary silicon particles. Heat treated structures rendered nano and ultrafine metal matrix composites. Findings: New developed as-cast Al-Si materials containing nano-diameter Si whiskers, without primary silicon particles required ultra short time heat treatment to result in nano and ultrafine metal matrix composite, rendering their hardness, strength and wear resistance, and the same time retaining toughness and ductility. Research limitations/implications: The cast samples were produced in laboratory conditions and potential tensile strength was estimated from empirical correlation with micro-hardness measurements. In the future, the comprehensive mechanical properties need to be tested. Practical implications: These ultrafine Si, Al-MMCs can be net-shape formed by modified HPDC technology or consolidated from spray-atomized alloy powder. Originality/value: Optimization of the entire production process for the hypereutectic Al-Si alloy compositions achieved a uniform distribution of ~ 25 vol.% of ultrafine Si particles in ductile FCC-Al matrix further reinforced by age hardening with nano-scale spinodal GP-zones. The associated mechanical property and ductility improvements will open a wide range of critical lightweighting components in transportation: aerospace, terrestrial vehicle and marine to the optimized hypereutectic Al-Si alloys. Presently, these components do not use the commercial HPDC A390 alloys due to their limited ductility and strength. Proposed new technology will allow conversion of various cast airspace alloys with ultrahigh mechanical properties to the automotive applications.

Application of a area -Approach for Fatigue Assessment of Cast Aluminum Alloys at Elevated Temperature

This paper contributes to the effect of elevated temperature on the fatigue strength of common aluminum cast alloys EN AC-46200 and EN AC-45500. The examination covers both static as well as cyclic fatigue investigations to study the damage mechanism of the as-cast and post-heat-treated alloys. The investigated fracture surfaces suggest a change in crack origin at elevated temperature of 150 ∘ C. At room temperature, most fatigue tests reveal shrinkage-based micro pores as their crack initiation, whereas large slipping areas occur at elevated temperature. Finally, a modified a r e a -based fatigue strength model for elevated temperatures is proposed. The original a r e a model was developed by Murakami and uses the square root of the projected area of fatigue fracture-initiating defects to correlate with the fatigue strength at room temperature. The adopted concept reveals a proper fit for the fatigue assessment of cast Al-Si materials at elevated temperatures; in detail, the slope of the original model according to Murakami should be decreased at higher temperatures as the spatial extent of casting imperfections becomes less dominant at elevated temperatures. This goes along with the increased long crack threshold at higher operating temperature conditions.

Aluminum and silicon based phase change materials for high capacity thermal energy storage

Six compositions of aluminum (Al) and silicon (Si) based materials: 87.8Al-12.2Si, 80Al–20Si, 70Al–30Si, 60Al–40Si, 45Al–40Si–15Fe, and 17Al–53Si–30Ni (atomic ratio), were investigated for potentially high thermal energy storage (TES) application from medium to high temperatures (550–1200 °C) through solid–liquid phase change. Thermal properties such as melting point, latent heat, specific heat, thermal diffusivity and thermal conductivity were investigated by differential scanning calorimetry and laser flash apparatus. The results reveal that the thermal storage capacity of the Al–Si materials increases with increasing Si concentration. The melting point and latent heat of 45Al–40Si–15Fe and 17Al–53Si–30Ni are ∼869 °C and ∼562 J g−1, and ∼1079 °C and ∼960 J g−1, respectively. The measured thermal conductivity of Al–Si binary materials depend on Si concentration and is higher than 80 W m−1 K−1 from room temperature to 500 °C, which is almost two orders of magnitude higher than those of salts that are commonly used phase change material for thermal energy storage.

Thermo-mechanical Experiments of Y-PSZ Thermal Barrier Ceramic Coating with Bond Coat of Alumina

In the present study, aluminum alloy (AlSi) substrates coated by Yttria stabilized zirconia used as thermal barrier have been investigated. The ceramic coating on the substrate is applied by plasma-spraying technique. Alumina (Al2O3) is used as a bond coat material. Four types of ceramic coating thickness (150, 250, 350 and 450 µm) were applied to AlSi materials which were cut out of diesel engine pistons with 100 µm thickness of bonding coat of Al2O3. The thermal torch and the thermal shock tests were conducted to coated samples which were made according to the international standards. Constant shock intensities were tested for 70 cycles on different thicknesses of the ceramic material and special attention was paid to the influence of thickness of the coating on the crazing phenomenon. Thermal resistance of thermal torch tested samples has been checked by drilling a hole in the middle of the samples and deformation time has been noted. Thermal shock tested samples were analyzed by X-ray diffraction machine and scanning electron microscopy machine. The diffractograms and micrographs have been obtained respectively for the samples. The diffractograms and micrographs of as sprayed samples and shock tested samples for different thickness have been compared, even the effect of thermal shock experiment on the different coating thickness of the ceramic have been analyzed. At the end of the tests, the most suitable ceramic coating thickness was determined.

SiC-based refractory paints prepared with alkali aluminosilicate binders

Refractory paints based on silicon carbide (SiC) were developed using inorganic alkali aluminosilicates binders. In order to optimize the binders, different raw materials have been tested for their preparations (calcined kaolin, commercial metakaolin, α-alumina and fumed silica synthetic powders). The alkali activator was an aqueous solution of KOH/K 2SiO 3. The SiO 2:Al 2O 3 molar ratio was equal to 4 and the SiO 2:K 2O molar ratio was 2. Calcined kaolin and metakaolin in alkaline conditions dissolved and re-precipitated to form geopolymer resins acting as a glue for the un-reacted Al–Si materials and SiC (90 wt.%). Binders based on α-alumina and fumed silica behaved as water glass. Binders and SiC paints were tested and characterized in inert and oxidative atmospheres up to 1300 °C. The oxidation of the SiC paints was 50% lower than that of pure SiC, evidencing a key role of the alkali aluminosilicate binders during the thermal treatments.

Catalytic activity and surface characteristics of layered Zn–Al–Si materials supported platinum

The present work aims at the preparation and characterization of novel catalysts based on layered double hydroxide structures (LDHs) containing Zn 2+, Al 3+ and Si 4+ cations in host layers and platinum species supported over the surface of these structures. LDHs with different Zn/Al/Si ratios were prepared via a co-precipitation method. Characterization of Zn–Al–Si layered double hydroxides was carried out using energy-dispersive X-ray spectrometry, X-ray powder diffraction, infrared spectra, thermal analyses and scanning electron microscopy. Experimental results revealed the presence of only crystalline phases of layered double hydroxides containing about 20–40 mol% of aluminum and silicon. These novel materials are commonly used as supports for platinum catalysts. Layered double hydroxide supported platinum samples were characterized through nitrogen adsorption–desorption, X-ray powder diffraction, infrared spectra and thermal analyses. The activity of the prepared platinum catalysts was tested through cyclohexane dehydrogenation and n-hexane cracking using a pulse flow system. Our results suggested that the Zn–Al–Si layered double hydroxides have a positive catalytic effect towards dehydrogenation.

A new method to evaluate the hydraulic activity of Al-Si materials

Slag, fly ash, gangue and 500°C calcined gangue are analyzed by using identical coupled plasma optical emission spectroscopy (ICP), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR) and magnetic angle spinning nuclear magnetic resonance (MAS NMR). Research results show that there is a negative linear relationship between the Si 2p and Al 2p binding energies of Al-Si materials and the compressive strength of aluminosilicate based cementitious materials prepared with these Al-Si materials, i.e. the lower the binding energies, the higher the compressive strength. Indeed, the Si 2p and Al 2p binding energies of Al-Si materials can be used to indicate their hydraulic activity. The binding energies of the four examined materials increase in the order of slag, fly ash, 500°C calcined gangue and untreated gangue. Moreover, the binding energies of Si 2p, Al 2p and O 1s of every Al-Si material have excellent correlation. By using the Al 2p binding energy and 27Al MAS NMR spectra, the coordination number of aluminum in slag is determined to be four, while that in gangue, is six. Based on the aforementioned discoveries, this paper presents a new effective method to evaluate the hydraulic activity of Al-Si materials by using the surface binding energies of silicon and aluminum of Al-Si materials.

Novel insights into the tribology of hypereutectic AlSi cylinder bore surfaces

Aluminium alloys remain highly attractive for weight reduction measures. Yet the fundamental mechanisms on the nanometre scale which dominate friction and wear are still largely unexplored. Using state-of-the-art surface analytical tools scientists at IAVF Antriebstechnik AG have studied the cylinder bore surface of a hypereutectic AlSi crankcase. These investigations led to a new model that is able to explain a number of wear phenomena of AlSi materials.

ダイキャスト法で作製したＡｌ‐Ｓｉ材料の熱特性

Recently heat spreader becomes more important for the heat diffusion of a micro processor unit (MPU). Physically, it needs a material with both low thermal expansion a and high thermal conductivity K. Although Cu-W, AIN and Al-SiC have hitherto been studied exhaustively as materials suitable for application in various heat spreaders, these materials have been limited to special uses because of a high price resulting from the complicated fabrication processes. Until now the study of heat spreader has hardly been made on Al-Si system, because this material tends to become more brittle and to make the fabrication more difficult as Si content increases, particularly in the composition range available for heat spreaders. Although there are such troublesome problems in Al-Si, we investigated both thermal conductivity K and thermal expansion a of Al-Si materials prepared by the conventional casting method. As a result, the Al-50Si material was found to have values of K = 150 W/m ⋅K and a =10 x10-6/K, respectively, which satisfy the thermal characterization required for heat spreaders. However the brittle Si phase in Al-50Si was needled to a length of about 0.5 mm, resulting in a marked lowering of tenacity. For this reason, the die casting method was employed to control the grain size, so that so precipitated Si phases became smaller needles of a length of approximately 30μm, leading to the effective improvement of tenacity.

Microstructural characteristics and mechanical properties of hypo-eutectic and hyper-eutectic Al–Si alloys in the semi-solid forming process

The characteristics of the globularization distribution and quantitative mechanical properties in the forming process of rheologically formed parts with an arbitrary shape need to be investigated to minimize occurrence of defects and to minimize subsequent machining. However, most of relevant research that has been performed is about the effects of die temperature and applied pressure on the filling behavior of semi-solid materials. Therefore, in the present study, the microstructures and mechanical behavior of Al–Si materials with wear resistance fabricated by the rheological forming (semi-solid forming) process are evaluated in terms of globularization and surface non-uniformity. The effect of alloy compositions and heat treatment on the mechanical properties is investigated for a part fabricated using the rheological forming process. The three-step reheating process for rheological forming was performed with wrought and cast aluminum alloys. The mechanical properties of the parts so formed are obtained for several locations by the tensile test and microstructure investigation.

Formation and evolution of weathering products in rhyolitic pyroclastic flow deposit, southern Kyushu, Japan.

Weathering reactions of a rhyolitic pyroclastic flow deposit in southern Kyushu, Japan were investigated in order to understand the behavior of elements and the formation and evolution of reaction products. The weathering profile developed in the pyroclastics contains variable amounts of erionite, halloysite and noncrystalline Al-Si-Fe-rich materials with or without noncrystalline Mn-rich material as weathering products. The formation of these products appears to reach depth of more than 10 m below the surface. The mobility of cations in this profile is Na>Ca>K>Si>Fe>Al>Ti>Mn, in which Al, Fe, Mn, and Ti accumulate mostly in the surface horizon during the weathering. The accumulation of these elements is caused by dissolution of volcanic glass, feldspar, and pyroxene, and precipitation of noncrystalline clays enriched in Al, Fe, Mn, and Ti. Aluminum and Si released into solutions from volcanic glass and feldspar tend to combine with each other to produce Al-Si complexes with high reactivity with other metal cations at the initial weathering stages. Fe2+ and Mn2+ derived mainly from pyroxene are incorporated with the Al-Si complexes and precipitate as Al-Si materials containing Fe and Mn exhibiting irregular aggregates of randomly elongated very fine noncrystalline fibers less than 0.1μm in length. These noncrystalline fibers tend to crystallize to halloysite by partial development of a domain structure and elimination of Fe and Mn during crystallization processes. This weathering profile characteristically contains erionite crystals exhibiting hexagonal rods and thin needles normally less than 5μm in length as a major weathering product of the rhyolitic pyroclastic flow deposit. The chemical compositions of erionite crystals show a wide range with negative correlation between numbers of Si and those of Al+Fe3++Ti in which Si content increases continuously with depth. These erionite crystals may have been formed in a micro-environment where high pH and high cation activity conditions have been achieved by heterogeneous dissolution of volcanic glass and feldspar.