Al Si System Research Articles

Investigation of self-diffusion and specific heat capacity of eutectic al-si systems using molecular dynamics simulations with ADP

Aluminum-silicon (Al-Si) alloys are of significant interest in various engineering applications due to their favorable mechanical properties and low density. Understanding the thermodynamic and transport properties of these alloys is essential for optimizing their performance in practical applications. In this study, an angular dependent potential (ADP) for Al-Si systems is employed to describe the atomic interactions and dynamics of an Al-Si alloy system. A set of molecular dynamics (MD) simulations are performed to explore the diffusion behavior of the Al-Si alloy at different temperatures, with a specific focus on the eutectic composition of the Al-Si system. The mean squared displacement (MSD) method is applied to calculate its diffusion coefficients, enabling a detailed analysis of the system’s atomic mobility and transport characteristics. Furthermore, the specific heat capacity of the Al-Si system is determined through energy fluctuation analysis, providing insights into the system’s thermodynamic behavior. The obtained diffusion coefficients play a vital role in predicting the kinetics of the eutectic solidification of Al-Si alloys, while the specific heat capacity will facilitate the understanding of the thermal behavior and the energy changes associated with the eutectic reaction in such alloys.

The impact of small Zr addition to Al–Ni cast alloy for elevated temperature applications

Most aluminium casting alloys are based on the eutectic system Al–Si, which has weak thermal properties. Alloys from the eutectic Al–Ni system on the other hand have higher thermal stability and good casting properties and are therefore promising for casting applications. Using casting simulations, a copper mold was designed to achieve cooling rates above 100 K/s with the aim of producing a Zr-rich supersaturated solid solution. Microstructural analysis revealed that the addition of Zr leads to notable changes in the microstructure characterised by the formation of primary Al3Zr and αAl dendrites. Subsequent heat treatment revealed that Zr-enriched alloys undergo significant age hardening, which showed an improvement in microhardness due to effective Al3Zr precipitation.

Selection of heat treatment and its impact on the structure and properties of AK10M2N–10%TiC composite material obtained via SHS method in the melt

The composite materials based on the Al–Si system alloys, strengthened with a highly dispersed titanium carbide phase, possess improved characteristics and belong to the group of promising structural materials. Currently, self-propagating high-temperature synthesis (SHS) based on the exothermic interaction, wherein titanium and carbon precursors directly involve in the melt, is the most accessible and effective method to obtain them. This paper proves the feasibility and demonstrates the successful synthesis of a 10 wt.% titanium carbide phase in the melt of the AK10M2N alloy, resulting in the AK10M2H-10% TiC composite material. Samples of the matrix alloy and the composite material were subjected to heat treatment according to the T6 mode, with various temperature-time parameters for hardening and aging operations. Based on the results, optimal heat treatment modes were selected to ensure maximum hardness. We studied the macroand microstructure of the obtained samples and performed micro X-ray spectral and X-ray diffraction phase analyses. Different groups of properties underwent comparative tests. It was established that the density of AK10M2N–10%TiC samples before and after heat treatment, according to optimal modes, is close to the calculated value. We showed that the combination of reinforcement and heat treatment significantly increases hardness, microhardness, and compressive strength, with a slight decrease in ductility. Additionally, it maintains the values of the coefficient of thermal linear expansion, high-temperature strength, and resistance to carbon dioxide and hydrogen sulfide corrosion at the level of the original alloy. The greatest effect was observed during the investigation of tribological characteristics: heat treatment of the composite material according to the recommended mode significantly reduces the wear rate and friction coefficient, eliminates seizure and tearing, and prevents temperature rise due to friction heating.

Thermal Stability of the Structural and Phase State of Aluminum and Alloys of the Al–Si System Doped with Zirconium Atoms under the Influence of Compression Plasma Flows

Thermal Stability of the Structural and Phase State of Aluminum and Alloys of the Al–Si System Doped with Zirconium Atoms under the Influence of Compression Plasma Flows

Aluminium-Silicon Lightweight Thermal Management Alloys with Controlled Thermal Expansion

With the ever-growing emphasis on global decarbonization and rapid increases in the power densities of electronics equipment in recent years, new methods and lightweight materials have been developed to manage heat load as well as interfacial stresses associated with coefficient of thermal expansion (CTE) mismatches between components. The Al–Si system provides an attractive combination of CTE performance and high thermal conductivity whilst being a very lightweight option. Such materials are of interest to industries where thermal management is a key design criterion, such as the aerospace, automotive, consumer electronics, defense, EV, and space sectors. This paper will describe the development and manufacture of a family of high-performance hypereutectic Al–Si alloys (AyontEX™) by a powder metallurgy method. These alloys are of particular interest for structural heat sink applications that require high reliability under thermal cycling (CTE of 17 μm/(m·°C)), as well as reflective optics and instrument assemblies that require good thermal and mechanical stability (CTE of 13 μm/(m·°C)). Critical performance relationships are presented, coupled with the microstructural, physical, and mechanical properties of these Al–Si alloys.

ДОСЛІДЖЕННЯ ЩІЛЬНОСТІ МАКРОСТРУКТУРИ ВИЛИВКІВ ІЗ ВТОРИННОГО СПЛАВУ СИСТЕМИ AL-SI ПРИ МОДИФІКУВАННІ ВИСОКОДИСПЕРСНИМ КАРБІДОМ КРЕМНІЮ

The study analyzes the impact of modifying a secondary aluminum casting alloy of the Al-Si system with high-dispersion silicon carbide on the density of the metal and the macrostructure of cylindrical castings. It was found that the solidification rate and the structure of the metal depend on the type of mold (metal or sand-clay) and the amount of added SiC. Alloys with a 0.1% SiC addition, cast in a metal mold, have the highest density. The macrostructure of SiC-modified castings is characterized by the presence of deep shrinkage cavities and concentrated porosity. Castings poured into a sand-clay mold with SiC modification show concentrated shrinkage and gas pores, which corresponds to a low grade on the reference scale. The study highlights the importance of choosing the casting method and alloy modification to optimize the density and structure of the castings.

Understanding the Electronic Transport of Al-Si and Al-Ge Nanojunctions by Exploiting Temperature-Dependent Bias Spectroscopy.

Understanding the electronic transport of metal-semiconductor heterojunctions is of utmost importance for a wide range of emerging nanoelectronic devices like adaptive transistors, biosensors, and quantum devices. Here, we provide a comparison and in-depth discussion of the investigated Schottky heterojunction devices based on Si and Ge nanowires contacted with pure single-crystal Al. Key for the fabrication of these devices is the selective solid-state metal-semiconductor exchange of Si and Ge nanowires into Al, delivering void-free, single-crystal Al contacts with flat Schottky junctions, distinct from the bulk counterparts. Thereof, a systematic comparison of the temperature-dependent charge carrier injection and transport in Si and Ge by means of current-bias spectroscopy is visualized by 2D colormaps. Thus, it reveals important insights into the operation mechanisms and regimes that cannot be exploited by conventional single-sweep output and transfer characteristics. Importantly, it was found that the Al-Si system shows symmetric effective Schottky barrier (SB) heights for holes and electrons, whereas the Al-Ge system reveals a highly transparent contact for holes due to Fermi level pinning close to the valence band with charge carrier injection saturation due to a thinned effective SB. Moreover, thermionic field emission limits the overall electron conduction, indicating a distinct SB for electrons.

Изучение технологии синтеза металлокерамического материала системы AlxFeySi

The current stage of development of the metal products market dictates the need to search for new materials with an improved set of performance characteristics using high technologies and publicly available raw materials. One of the promising materials with an attractive set of properties is ceramics of the MeSi type (silicides). Materials from this group have high hardness and wear resistance. The study of alloys of the Al-Si system containing elements such as iron, copper, manganese is one of the promising areas in metallurgy and materials science. To solve the problem of improving the quality of aluminum-based parts, it was decided to use AlxFeySi composite ceramic material. In this work, using the principles of additive technologies, an experimental batch of metal-ceramic materials is obtained, which has a typical cast microstructure with a set of phases inherent in the system under consideration. It was found that the hardness of the resulting material is 541.7 Vickers units, exceeding the hardness of the steel-substrate by 2 times

CHANGES IN THE STRUCTURE AND PROPERTIES OF ALUMINIUM ALLOYS WHEN MODIFIED WITH POWDER COMPOSITIONS

Purpose. To determine the effect of modification with powder compositions on the structure and mechanical properties of cast and deformed aluminium alloys. Research methods. Metallographic analysis, stereometric metallography, testing of strength and plastic properties of cast alloys AL4, AL4C of the Al-Si system and deformed alloys 1545 of the Al-Mg-Sc system, 2219 of the Al-Cu-Mn system in their original and modified state. Results. Meltings of AL4, AL4C, 1545, 2219 alloys were carried out in the initial state and with melt treatment with a complex nano-disperse modifier of magnesium silicide Mg2Si and silicon carbide SiC with a particle size of 50...100 nm. The optimal content of Mg2Si+SiC (0.10%) for increasing σ0.2 of aluminium alloys was determined. A 1.6-fold reduction in the grain structure of cast alloys was achieved. The dependence of the particle size and the amount of the modifier on the mechanical properties of the alloys was established. In industrial experiments, the most effective particle size of Mg2Si+SiC was established for increasing σ0.2 of AL4, AL4C alloy from 115 to 260 MPa in the as-cast state. The increase in the strength properties of the modified alloys is 44 % compared to the original state. Scientific novelty. Further development, insight into the influence of melt modification on the parameters of the structure and properties of aluminium alloys was obtained. The use of nanodispersed complex modifier Mg2Si+SiС with a particle size of 50...100 nm is proposed. It has been confirmed that the use of complex nanodisperse modifiers allows you to actively influence the structure and mechanical properties of aluminium alloys. Practical value. It has been experimentally proven that the rational amount of the introduced complex modifier is 0.10% of the mass of the melt. A significant grinding of the grain structure and an increase in the strength properties of cast and deformed aluminium alloys were achieved as a result of the modification.

Electronic Structure of Li, Be, and Al Ultrathin Coverings on the Si(100) Surface

Within the framework of density functional theory and the pseudopotential method, calculations of the density of electronic states of the system “Si(100) substrate plus disordered two-dimensional metal layers (Li, Be or Al)” with a thickness of one to four single-atomic layers were carried out during growth at 0°K. It is shown that the electronic structure of the first single-atomic layers of these metals on Si(100) has band gaps. The maximum band gap was found in the Be-Si system (1.03 eV for a single-atomic layer). In this system, the band gap disappears when four single-atomic layers are deposited. In the Li-Si system (0.98 eV for a single-atomic layer) it disappears for two single-atomic layers. In the Al-Si–system (0.50 eV with four single-atomic layers), the band gap disappears for three single-atomic layers. This behavior of the band gap can be explained by the passivation of the substrate surface states and the peculiarities of the electronic structure of the adsorbed metals.

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.

Sub-nano Layers of Li, Be, and Al on the Si(100) Surface: Electronic Structure and Silicide Formation

Within the framework of the density functional theory and the pseudopotential method, the electronic structure calculations of the “metal-Si(100)” systems with Li, Be and Al as metal coverings of one to four monolayers (ML) thickness, were carried out. Calculations showed that band gaps of 1.02 eV, 0.98 eV, and 0.5 eV, respectively, appear in the densities of electronic states when the thickness of Li, Be and Al coverings is one ML. These gaps disappear with increasing thickness of the metal layers: first in the Li-Si system (for two ML), then in the Al-Si system (for three ML), and then in the Be-Si system (for four ML). This behavior of the band gap can be explained by the passivation of the substrate surface states and the peculiarities of the electronic structure of the adsorbed metals. In common the results can be interpreted as describing the possibility of the formation of a two-dimensional silicide with semiconducting properties in Li-Si(100), Be-Si(100), and Al-Si(100) systems.

Effects of ErF3 Particles on the Structure and Physicomechanical Properties of A359 Alloy

In this work, the impact of ErF3 submicroparticles on the microstructure and mechanical properties of the A359 alloy was studied. ErF3 particles provided a homogeneous structure in castings produced via the casting method. The modifying effect of ErF3 particles on the structure of Al–Si alloys is realized through the mechanism of restraining the crystallization front and is achieved through the reduction in the formation of clusters of iron phases and eutectic lamellar silicon. It was found that the addition of 1 wt% ErF3 to the A359 alloy leads to a decrease in the average grain size by 21% and an increase in the yield strength by 14%, in tensile strength by 16%, in the microhardness of Al15(FeMn)3Si2 phase by 34% and in the Al15(FeMnCr)3Si2 phase by 7%. The heat treatment of the A359 alloy with ErF3 particles increased the yield strength by 36% and the tensile strength by 34%. The absence of an effect of ErF3 particles on the hardness values of the A359 alloy, as well as on the fracture process of the A359 alloy, was observed. The negative influence of ErF3 particle agglomerates and clusters on the strength characteristics of the investigated alloys was observed. Approaches for further exploring the potential of ErF3 particles as a strengthening phase in cast aluminum alloys of the Al–Si system were proposed.

Mechanical and Microstructure Characterisation of the Hypoeutectic Cast Aluminium Alloy AlSi10Mg Manufactured by the Twin-Roll Casting Process

Multi-material designs (MMD) are more frequently used in the automotive industry. Hereby, the combination of different materials, metal sheets, or cast components, is mechanically joined, often by forming joining processes. The cast components mostly used are high-strength, age-hardenable aluminium alloys of the Al–Si system. Here, the low ductility of the AlSi alloys constitutes a challenge because their brittle nature causes cracks during the joining process. However, by using suitable solidification conditions, it is possible to achieve a microstructure with improved mechanical and joining properties. For this study, we used the twin-roll casting process (TRC) with water-cooled rollers to manufacture the hypoeutectic AlSi10Mg for the first time. Hereby, high solidification rates are realisable, which introduces a microstructure that is about four times finer than in the sand casting process. In particular, it is shown that a fine microstructure close to the modification with Na or Sr is achieved by the high solidification rate in the TRC process without using these elements. Based on this, the mechanical properties increase, and especially the ductility is enhanced. Subsequent joining investigations validate the positive influence of a high solidification rate since cracks in joints can be avoided. Finally, a microstructure-property-joint suitability correlation is presented.

Dy–Al–Si System: Experimental Study of the Liquid–Solid Phase Equilibria in the Al-Rich Corner

The Dy–Al–Si ternary system has been experimentally studied, as the effect of the dysprosium addition on the constitution and topology of the liquidus surface, focusing on the (Al) rich part. The system has been investigated in a composition range of up to about 58 at% silicon. The alloys constitution and the liquidus surface projection have been determined by means of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), X-ray powder diffraction (XRPD), and differential thermal analysis (DTA). This work is part of a research framework on the properties and solid–liquid phase equilibria of the R Al–Si (R: rare earth) systems. These data, along with the ternary systems isothermal section, are needed to outline the design, plan, and development of new Al–Si-based alloys. In the Dy–Al–Si system, four primary crystallization fields have been experimentally detected: (Si), DyAlxSi(2−x) (orthorhombic form), Dy2Al3Si2 (Τ2), and DyAl(3−x)Six. The following three invariant equilibria have been identified: at 566 °C the ternary eutectic L ⇆ DyAl2Si2 + (Al) + (Si), at 630 °C the U1 L+ DyAl3 ⇆ Dy2Al3Si2 + (Al), and at 562 °C the U2: L+ Dy2Al3Si2 ⇆ DyAl2Si2 +(Al) reactions. A comparison with other known R Al–Si systems has been conducted.

Tension–Compression Flow Asymmetry as a Function of Alloy Composition in the Al-Si System

Tension–Compression Flow Asymmetry as a Function of Alloy Composition in the Al-Si System

Vacuum High-Temperature Brazing of 3003 Aluminum Alloy

Brazing filler metals based on the Al-Si system are widely used for brazing aluminum alloys. Their melting point is 577 °С (eutectic). It is necessary to conduct comprehensive studies of the technological properties of experimental filler metals and brazed joints to create a brazing filler metal with a reduced melting temperature for vacuum brazing of thin-walled aluminum products made of alloy 3003. The paper presents the research results on high-temperature vacuum brazing of aluminum alloy 3003 with Al-Cu-(Si, Mg) filler metal. It was determined that the amount of magnesium in the filler should be limited due to the risk of porosity formation associated with magnesium vaporization. It was identified that reducing the magnesium content increases the liquidus temperature above 530–550 °C. Therefore, experimental alloys require additional alloying with depressant elements, particularly silicon, to achieve the required melting temperature level. The chemical inhomogeneity of the filler in the initial state (after rapid solidification from the liquid state) and the structure of the brazed joints were investigated using micro-X-ray spectral analysis. Through empirical means, it was determined that a magnesium content of 1.5 % by weight in the filler allows for producing high-quality brazed joints without visible defects. In this case, shear strength is in the range of 0.6–0.7 of the strength of the base material. Tests of brazed joints for three-point bending resulted in an angle close to 180°, which indicates the promising use of experimental brazing filler metal in vacuum brazing of aluminum alloy 3003.

Experimental study of the effect of the simultaneous treatment of the melt with different currents on the quality indicators of castings

The purpose of the work is to obtain results that would confirm the effectiveness and perspective of using the method of simultaneous treatment of a liquid alloy based on Al with different types of currents in foundry technologies. As it is known the different types of current passing through the melt (alternating, constant, pulsed) are differ from each other by their different functional capabilities. The each types of currents generate electromagnetic fields with different amplitude-frequency characteristics and distribution, which determine the sphere of influence. The work proposed to use an innovative principle of simultaneous passing of at least two currents with different electrical characteristics through the melt and with different variants of electrode systems. This method made it possible to affect more effectively on the structure and properties of the melt and, in turn, improve the service characteristics of the casting. In the work, two series of experiments were performed with the application of melt treatment with three types of currents and three types of electrode systems in different combinations. Ingot alloys of the Al-Si system was treated: AK7 (GOST 1583-93), chemical composition: Si (7.3 %); Fe (0.5 %); Cu (0.5 %); Mn (0.07 %); Mg (0.07 %); Zn (0.2 %); Pb (0.01 %), Al base; and non-standard pre-eutectic silumin additionally doped with certain components (Si (8 %); Fe (0.79 %); Cu (1.98 %); Mn (0.1 %); Mg (0.27 %); Zn (0.44 %), Al base). In contrast to the treatment of one type of current, an increase the mechanical properties of castings and an effective modification of the elements of the solid state structure were achieved. Thus, for the first grade of alloy, σВ was increased by 13 %, and δ — by 1.5 times. Also after simultaneous treatment with different types of currents with defined modes, the value of Ψ was recorded at the level of 4.4 %. For the AK7 alloy, this indicator is not even specified by the standard. For the second grade of alloy, after simultaneous treatment with different types of currents, significant grinding of intermetallics to sizes from 8 μm to 11 μm was observed, while compared to the original sample, there is practically no segregation of the intermetallic component by size. The structure of the treated samples is distinguished by the grinding of silicon particles in the eutectic. The total energy consumption, under certain conditions, for both brands of alloys was reduced by 3 times. The main mechanism of a positive change in the crystallization ability of the melt is formation of electromagnetic fields superposition with more powerful thermoforce effect in the treatment object by passing different types of currents simultaneously than when using one type of current.

Assessment of the Possibility of Galvanic Corrosion in Aluminum Microchannel Heat Exchangers

As part of the work, three used microchannel heat exchangers from different manufacturers were analyzed. For comparison purposes, the new heat exchanger was also subjected to the NSS salt spray test. The material of the Al-Si system used for brazing, as well as the material of the core, were subjected to electrochemical tests. In laboratory tests, polarization curves were determined for the Al-Si material used for brazing, as well as for the core material. On the basis of exchanger research, it was found that a critical problem in the use of microchannel exchangers is galvanic corrosion occurring in the areas of brazed joints. Electrochemical tests have shown that the Al-Si alloy used for brazing has a lower value of corrosion potential than the core material. The existing potential difference is sufficient for galvanic corrosion. Electrochemical corrosion is initiated in the eutectic structure. The soplid solution is the anode and is particularly susceptible to corrosion, which led to its preferential dissolution in the entire volume of the eutectic mixture.

Crystalline aluminum silicides with electride state and superconductivity under high pressure

Metal-containing silicides are of fundamental interests in the fields of physics, chemistry, and material science due to their exotic structures and unique properties, such as electride state or superconductivity. However, crystalline compounds of elemental Al and Si remain poorly understood despite their abundance on Earth as well as Earth's interior where the pressure is dominated. In this work, we carry out an exhaustive research on the pressure-stabilized compounds of the Al–Si system through an advanced structural searching approach assisted with first-principal computations. Unexpectedly, a plethora of hitherto unknown metallic aluminum-silicon crystal phases (i.e., Al5Si, Al3Si, Al2Si, Al3Si2, AlSi, Al2Si3, AlSi2, AlSi4, AlSi6, and AlSi8) were identified with fascinating silicon motifs containing from isolated atom, ladder-like arrangement, linear chain, to three-dimensional framework. Our simulations further reveal the electride behaviors in Al5Si, Al3Si, Al2Si, and Al3Si2, in which Al could donate its valence electron into interstitial regions. Remarkably, Al2Si3 is predicted to possess a high superconducting critical temperature of 16 K at a relatively low pressure of 5 GPa, which allows it to become the best metal-silicon binary superconductor under high pressures. The present results provide a comprehensive understanding of metal-bearing silicides and will stimulate the future investigation and verification of our newly predicted metal silicides.