Al-Si Alloys Research Articles

Grain refiner fabricated by spark plasma sintering for hypoeutectic Al-Si alloy cast and its refining ability

Grain refiner fabricated by spark plasma sintering for hypoeutectic Al-Si alloy cast and its refining ability

Effect of friction stir processing on grain refinement and superplastic properties of binary Al-8 wt.% Si to Al-30 wt.% Si alloys

ABSTRACT As-cast binary Al–Si alloys containing ∼8, 12, 20, and 30 wt.% Si, representing the hypoeutectic, eutectic (12 wt.% Si), and hypereutectic compositions, were subjected to severe plastic deformation by friction stir processing (FSP) for grain refinement to 2.3–2.7 μm by dynamic recrystallization. Tensile tests conducted by differential strain rate test technique over the strain rates of 10−4 – 10−2 s−1 and test temperatures in the range of ∼840–530 K led to strain rate sensitivity index (m) varying from ∼0.04 to 0.40 depending on temperature, strain rate, and alloy composition. The constant initial strain rate tests conducted at 10−4 s−1 and 840 K exhibited a maximum elongation of 250% in the hypereutectic Al–20Si alloy, but the same increased linearly with m irrespective of alloy composition. Generally, with increasing Si content, the activation energy for deformation increased from 104.7 ± 14.4 kJ/mol for eutectic Al–12Si to 310.4 ± 32.3 kJ/mol for hypereutectic Al–30Si, which increased further to 572 ± 148 kJ/mol over the higher temperature range of 840–800 K. Analysis of observed deformation and microstructure behaviour supports the occurrence of superplasticity, whereby the accommodation of grain boundary sliding by grain boundary migration led to enhanced grain growth or else the local high-stress concentration at the particle-matrix interface led to cavity formation. There was no evidence of dynamic recrystallization during high-temperature tensile deformation but the flow softening observed is ascribed to the occurrence of concurrent cavitation.

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.

Review of Wear and Mechanical Characteristics of Al-Si Alloy Matrix Composites Reinforced with Natural Minerals

Al-Si alloys are vital in the aerospace and automotive industries due to their high strength-to-weight ratio, excellent ductility, and superior corrosion resistance. These properties, along with good thermal conductivity, low thermal expansion, and enhanced wear resistance due to silicon, make them ideal for lightweight, high-performance components like engine parts exposed to harsh conditions and thermal cycling. In recent years, the development of aluminium metal matrix composites using Al-Si alloys as the base material has gathered significant attention. These composites are engineered by integrating various reinforcing particles into the aluminium matrix, which results in remarkable improvements in the wear resistance, hardness, and overall mechanical performance of the material. The stir casting process, a well-established and cost-effective method, is frequently employed to ensure a uniform distribution of these reinforcing particles within the matrix. This review delves into the influence of different types of reinforcing particles on the properties of Al-Si alloy-based AMCs. The incorporation of these reinforcements has been shown to significantly enhance wear resistance, reduce friction, and improve the overall strength and toughness of the composites, making them ideal candidates for high-performance applications in the automotive and aerospace sectors. Moreover, this review highlights the challenges associated with the fabrication of these composites, such as achieving a homogeneous particle distribution and minimizing porosity. It also discusses the latest advancements in processing techniques aimed at overcoming these challenges. Additionally, this review addresses the potential environmental and economic benefits of using natural reinforcements, which not only reduce material costs but also contribute to sustainable manufacturing practices.

Effects of Strontium Modification on Corrosion Resistance of Al-Si Alloys in Various Corrosive Environments.

This study investigates the impact of strontium (Sr) additions on the corrosion resistance of an LM6 (A413) aluminium alloy. By incorporating varying concentrations of Sr (0.01 wt.% and 0.05 wt.%), the morphological and corrosion behaviours of the alloy were analysed under different corrosive environments, including sulphuric acid, sodium hydroxide, and sodium chloride solutions. The results demonstrate that Sr modifications significantly enhance the alloy's corrosion resistance, with the most substantial improvement observed at 0.05 wt.% Sr. The analysis revealed that the weight loss of the alloy in sulphuric acid decreased by 2.5% with 0.05 wt.% Sr after 10 days of immersion, due to the formation of a stable passive oxide layer. In sodium hydroxide, however, the weight loss was reduced by 5% with 0.05 wt.% Sr after 10 days, indicating aggressive uniform corrosion. In the 3.5% sodium chloride solution, the corrosion rates remain relatively low, and the 0.05 wt.% Sr alloy showed a decrease in corrosion product formation over time, suggesting enhanced resistance. Detailed surface analyses, including 3D profiling and morphology assessments, revealed that Sr additions refine the eutectic silicon phase, transforming it from a coarse to a more desirable fibrous or lamellar structure, thus improving the alloy's overall performance. The innovative findings underscore the potential of Sr as an effective microstructural modifier for enhancing the durability and longevity of Al-Si alloys in corrosive environments.

Drimia maritima as a New Green Inhibitor for Al-Si Alloy, SAE Steel and Pure Al Samples in 0.5 M NaCl Solution: Polarization and Electrochemical Impedance Analyses

The corrosion inhibition effects of Drimia maritima (L.) Stearn sin. Urginea maritima (L.) Backer on three different materials, i.e., as-cast Al-7 wt.% Si alloy, SAE 1020 low carbon steel, and commercially pure Al samples, into a stagnant and naturally aerated 0.5 M NaCl solution are evaluated. For this purpose, both the potentiodynamic polarization curves and electrochemical impedance spectroscopy with an equivalent circuit are utilized. It is found that inhibition effect increases up to certain minor Drimia maritima content. Adsorption isotherms (e.g., Langmuir and Temkin) indicate that all three examined materials comprise physical adsorption mechanisms. Al-Si alloys attained inhibition efficiencies of about 96% at 25 °C with 1250 ppm of Drimia maritima and ~43% with 625 ppm at 45 °C. On the other hand, the cp. Al and SAE 1020 samples attain ~89% and 68% with 1250 ppm and 500 ppm at 25 °C, respectively. This clearly indicates that the dosage of Drimia maritima green inhibitor into NaCl solution possesses certain susceptibility for each distinctive material examined. Impedance parameters obtained by using CNLS (complex non-linear least squares simulations) are correlated and discussed.

Enhanced Combustion Properties of Al-Si Eutectic Alloy in Energetic Mixtures

This study investigates the feasibility of using an Al-Si eutectic alloy as a reactive fuel in energetic mixtures. Al-Si eutectic alloy powders were obtained from secondary resources and ground to a particle size of less than 100 μm. We examined these powders’ burning characteristics and thermal properties compared to pure Al powder. Results showed that the burning rate of energetic mixtures containing Al-Si eutectic alloys was 1.5 to 2.0 mm/s higher than those with pure Al. Additionally, the activation energy of pure PTFE was reduced from 81.29 kJ/mol to 61.75 kJ/mol when the Al-Si alloy was added. The formation of oxides, carbides, and fluorides in the combustion products of Al-Si-based mixtures significantly influenced their thermodynamics.

Enhancing high-temperature strength in Al-Si alloys: The critical role of vanadium

Al-Si alloys are widely utilized in casting applications across various industries due to their favorable properties. This study addresses the imperative for improving the high-temperature strength of these alloys to expand their applicability. The stability of the microstructure of such alloys at elevated temperatures is closely associated with the diffusivity of their constituent elements. We explored the role of vanadium (V), which is known for its low diffusivity within the aluminum matrix, in enhancing the high-temperature strength of the Al-7Si alloy. The research evaluated mechanical properties, thermal stability, and fractographic characteristics of alloys. Microstructural analysis was conducted using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron backscatter diffraction (EBSD), with a focus on identifying the strengthening mechanisms. Our results demonstrate that the incorporation of 0.5 wt% V significantly enhances the mechanical properties of alloys at both ambient and elevated temperatures. This improvement is primarily due to the formation of Al10V intermetallic particles, which hinder dislocation movement and increase dislocation density during deformation. Notably, the presence of twinning within Al10V contributes to a more uniform stress distribution, and it alleviates the typically detrimental effects on ductility observed with conventional brittle intermetallics. The joint addition of 0.2 wt% Ti and 0.5 wt% V further intensifies these benefits by increasing the number density of Al10V intermetallic particles. Our study highlights the considerable promise of V in improving the performance of aluminum alloys for high-temperature applications.

Synergetic Effect of La and Sb on the Eutectic Silicon and Mechanical Properties in Multi-elements Hypoeutectic Al–Si Alloy

Synergetic Effect of La and Sb on the Eutectic Silicon and Mechanical Properties in Multi-elements Hypoeutectic Al–Si Alloy

Construction of Al–Si interatomic potential based on Bayesian active learning

Nanoscale simulations for optimizing the performance and processing of Al–Si alloys are currently facing two major obstacles: the scarcity of high-quality semi-empirical potentials tailored to complex alloy systems, and the prohibitively high computational cost associated with ab initio molecular dynamics simulations. In order to enhance simulation efficiency and accuracy of the Al–Si alloys’ microstructural evolution, this study employs a dynamic active learning technique, FLARE, to develop a non-parametric machine learning potential that combines the high accuracy of density functional theory (DFT) with the efficiency of classical molecular dynamics (MD). Without relying on extensive initial ab initio molecular dynamics data or existing databases, collection of the necessary data is progressively made during the active learning process, thereby constructing a potential capable of accurately simulating the structure and dynamics of high-temperature Al–Si alloys. By comparing with experimental measurements and ab initio molecular dynamics calculations, the high accuracy and computational efficiency of this potential is demonstrated in predicting energy, force, structure, and dynamic properties. The results provide novel theoretical insights for optimizing Al–Si alloy processing and underscore the usefulness of active learning methods in constructing high-accuracy potentials.

Al(Si)/Al2O3 and NiAl(Si)/Al2O3 co-continuous composites obtained by low temperature Reactive Metal Penetration of dense silica preforms.

Interpenetrating network Al(Si)/Al2O3 composites, obtained by a reactive metal penetration process, where pure aluminum metal reacts with a dense amorphous silica preform, are an interesting class of metal/ceramic composites, with two continuous networks of metal (Al-Si alloy) and ceramic (Al2O3). These composites have high stiffness and hardness, while retaining acceptable toughness and good thermal and electrical conductivity, and can be used in wear or thermal management applications. A second infiltration step with nickel allows to substitute the Al(Si) alloy with an intermetallic, obtaining an interpenetrating network NiAl(Si)/Al2O3 composite, with very high hardness and melting point. While in the standard process the temperature for obtaining the Al(Si)/Al2O3 composites is in the 1100-1200 °C range, in this paper we studied instead the 700-1000 °C temperature range and its effect on the microstructure of the final NiAl(Si)/Al2O3 composite. After the first infiltration step, the microstructure of Al(Si)/Al2O3 composites depends on both temperature and time of the treatment. At 700-800 °C and for reaction time of 1-2 hours, the grain size is completely sub-micrometric. When temperature and time of reaction increase, islands with a coarser microstructure, of micrometric size, form, reaching a fully micrometric coarser microstructure at 1100-1200 °C. The islands formation is due to the transformation from transition aluminas, formed at low temperature and low reaction time, to α-alumina, while at high temperature α-alumina forms directly. In a second step, the Al(Si) metal network was replaced with an intermetallic one, by contacting the composite with liquid nickel, that reacted with the Al(Si) alloy forming an Al-Ni-Si intermetallic. The temperature and duration of the first infiltration step strongly influences not only the microstructure of the Al(Si)/Al2O3 composite but also of the final NiAl(Si)/Al2O3 one, that is finer when the first step (reaction of aluminum with silica) occurs at lower temperature.

Friction and wear characteristics of DLC-terminated coatings deposited on AlSi10Mg alloy produced by Additive Manufacturing

Al–Si alloys are attractive materials for the fabrication of mechanical components, mainly because of their high strength-to-density ratio. Though the advent of Selective Laser Melting (SLM) has potentially expanded the range of their applicability, their poor tribological performances limit their effective use. Identifying post-processing protocols and coating strategies enhancing these properties and compatible with large-scale production is fundamental to the industrial uptake of SLM-fabricated Al–Si parts. This work tests the possibility of depositing self-lubricating Diamond-Like Carbon (DLC)-terminated films on AlSi10Mg built by SLM and subjected to different surface finishing processes. The applied coating architectures consist of an electroless nickel‐phosphorus buffer layer deposited on the AlSi10Mg surface, plus a series of interlayers and a DLC top film grown by Plasma Assisted – Chemical Vapor Deposition. The wear resistance and frictional behavior of the samples are evaluated for different substrate pre-treatments and coating assemblies under two applied loads. Cast substrates, processed and coated in a similar way, are also studied for comparison. The DLC film lends good tribological performances to all the coating-substrate combinations explored, being mechanically assisted by the underlying Ni–P layer. The friction coefficients stabilize around 0.20 at the lowest load, independently of the sample surface roughness (Sq), which spans the range 0.47–4.6 μm. Conversely, the counterpart wear rates increase with roughness up to 10−5 mm3/(N⋅m). Both tribological parameters decrease by nearly 20 % and 70 %, respectively, after a tenfold increase in load. These results indicate that DLC-terminated multilayers are extremely efficient on AlSi10Mg even in the presence of significant roughness. Their application requires a limited number of well-established processing steps also in the case of SLM grown parts.

Nanoparticle-enabled additive manufacturing of high strength 6061 aluminum alloy via Laser Powder Bed Fusion

Wrought aluminum alloy AA6061 is widely used in automotive, aerospace, and other industries due to its good properties, including high strength, excellent corrosion resistance, and good weldability. However, when using Laser Powder Bed Fusion (LPBF) for AA6061, hot cracking becomes a serious problem. In this work, AA6061 powder with internally dispersed nanoparticles has been adopted in a LPBF process. Through optimization of printing parameters, components with minimal porosity (less than 0.5 %) have been successfully produced without cracks. Additionally, by employing a chessboard printing strategy to create finely detailed cellular and grain structures, we have achieved significantly enhanced mechanical properties in its as-printed state for AA6061. These components exhibit an impressive yield strength (YS) of 233 MPa and ultimate tensile strength (UTS) of 310 MPa while maintaining a ductility of approximately 10 %. This performance surpasses that of commercial AA6061 and other Al-Si alloys, establishing it as a high-strength material suitable for various applications.

Thermal conductivity of binary Al alloys with different alloying elements

This work investigates the physical properties of several binary Al-Si/Ni/Fe/Cu/Mg alloys with varying alloying element contents and microstructures. The findings indicate that as the content of alloying elements increases, the number of secondary phases in binary Al alloys rises, and these phases become coarser. In hypereutectic compositions, primary phases in Al-Ni and Al-Fe alloys take on a needle-like morphology with high aspect ratios, forming a dendritic network. Regarding properties, in the hypoeutectic region, both thermal conductivity and electrical conductivity of binary alloys initially decrease sharply, followed by a more gradual decline with the addition of alloying elements. This trend occurs because thermal conductivity is mainly influenced by supersaturated solid solutions. In hypereutectic Al-Ni and Al-Fe alloys, the presence of large, needle-like primary phases significantly hinder the heat transfer, resulting in a more apparent reduction in both thermal conductivity and electrical conductivity. Among the five binary alloys, Al-Ni and Al-Fe alloys, which have lower solute concentrations of alloying elements in the Al matrix, exhibit the highest thermal and electrical conductivity. Furthermore, with increasing alloying element contents, the phonon thermal conductivity of Al-Si alloy increases more markedly compared to other alloys. The study will offer a fundamental understanding for the development of advanced alloy.

INTERLAYER EFFECT ON DEFORMATION AND FRACTURE OF DENDRITIC STRUCTURE FORMED DURING WIRE-FEED ELECTRON-BEAM ADDITIVE MANUFACTURING OF AL-SI ALLOY

Interfaces and surfaces play an important role in tribology, mechanics and materials science, causing plastic strain localization and stress concentration of different spatial scales. The interfacial inhomogeneity is highly pronounced in 3D printed materials due to thermo-cycling and layer-by-layer building. In this paper, the inlayer and interlayer structure of a eutectic Al-Si alloy fabricated by wire-feed electron-beam additive manufacturing is investigated by optical and electron microscopy. Model structures inheriting the experimental morphology are created, and their deformation and fracture are simulated using ABACUS/Explicit, with the user-defined subroutines being developed to describe the constitutive behavior of aluminum dendrite, silicon and eutectic materials. A two-scale computational approach is implemented to study the influence of the interlayer formed in the heat-affected zone on the dendritic structure strength.

Effect of N2/Ar Ratio on Wear Behavior of Multi-Element Nitride Coatings on AISI H13 Tool Steel.

In this study, multi-element nitride coatings composed of (Ti, Cr, Cu, Al, Si)N were synthesized on H13 tool steel using cathodic arc deposition (CAD) technology. The N2/Ar flow ratio varied from 0 to 2 as the experimental parameter, and two targets, Ti-Cr-Cu and Al-Si alloys, were utilized simultaneously. The impact of the gas flow ratio on the coatings' abrasion properties was investigated, focusing on aspects, such as chemical composition, adhesion, hardness, and wear behavior. The experimental findings indicate that the coated specimens with a nitrogen reaction exhibit superior hardness and abrasion resistance compared to those without nitrogen use. While the surface roughness of the specimens tends to increase slightly with a higher N2/Ar ratio, the coating demonstrates improved hardness, adhesion, and abrasion resistance performance. In summary, the wear-resistant characteristics of H13 tool steel can be significantly enhanced when applying a CAD-(Ti, Cr, Cu, Al, Si)N film with a flow ratio of N2/Ar = 2.

Investigation into the hydrogen inhibition mechanism of Platycladus orientalis leaf extract as a biodegradation inhibitor for waste aluminum-silicon alloy dust in wet dust collectors

This study investigates the risk of hydrogen explosion caused by waste metal dust encountering water in wet dust collectors. It proposes using renewable plant extracts to suppress hydrogen evolution from aluminum-silicon (Al-Si) alloy dust, aiming to achieve intrinsically safer production. Platycladus orientalis leaf extract (POLE) was prepared using water as a solvent. Hydrogen inhibition experiments, material characterization, and theoretical calculations were conducted to evaluate the effect of POLE on waste Al-Si dust. The inhibition experiments demonstrated that POLE exhibits excellent inhibitory performance. At a POLE concentration of 2.0 g/L, the hydrogen inhibition efficiency reaches 97.71 % after 22 h, with a reaction rate constant of 8.9708 × 10−5, approaching zero. This efficiency remained stable over 5 days. POLE formed a uniform, dense protective film on the Al-Si dust surface, with a contact angle of 99.23°. FTIR spectra revealed absorption peaks corresponding to POLE functional groups and Al-O bonds, indicating that successfully adsorption of POLE through both physical and chemical interactions. Finally, theoretical calculations were performed to further explain the hydrogen inhibition mechanism of POLE, supplementing and confirming the characterization data. This study inhibited hydrogen production from waste dust, offering a new approach to enhancing the hydrogen production rate from recycled Al scraps.

Research into the Structure and Adhesion of WCCoCr Coatings Plasma-Sprayed onto Castings of AlSi Alloy Plates

The article presents structural investigations and mechanical properties of hard coatings deposited by spraying WCCoCr powder in an argon-hydrogen plasma jet onto the surfaces of AlSi10Mg alloy casting plates. Two variants (A and B) of processing parameters of the powder spraying process onto the surface of silumin plates were applied, resulting in different coating thickness. The coating applied according to variant A was done with 12 passes, and its thickness was approximately 150 μm. The coating applied according to variant B was done with 20 passes, and its thickness was about 320 μm. The microstructures of these coatings are similar, consisting of wavy, alternately deposited phases of solid solutions with varying concentrations of elements, and fine spherical phases, irregularly dispersed carbides. A qualitative analysis of the distribution of microstructure components was performed based on surface mapping. Precipitates differing in their degree of grayness and shape were identified based on microanalysis of their chemical composition. The porosity assessment of coatings performed in five randomly selected areas amounts to an average of 9%. The applied coatings exhibit good adhesion to the substrate, as evidenced by the absence of delamination during scratching tests using a diamond Rockwell indenter loaded with a force of 10 N. The coating hardness averaged 1180HV0.2. The test results indicate the high quality of the WCCoCr coatings, regardless of their thickness.

Microstructure evolution in A356 alloy subjected to controlled heat treatment regimes processes

Aluminium–silicon alloys are highly regarded for their lightweight and unique mechanical properties, making them crucial for various industrial applications. Achieving optimal mechanical behavior in Al-Si-based alloys necessitates meticulous control over their microstructure. The research investigated the impacts of heat treatment regimes on the microstructure of A356 hypoeutectic alloys by light optical microscope (OM), scanning electron microscope (SEM), and energy dispersive spectroscope (EDS). The alloy, produced via stir-casting, underwent homogenization at 540 °C/5 h, one-step (200 °C for 0.5–8 h (T1)) and two-step (T2 (200 °C/0.5 h/180 °C/0.5–8 h)), and T2L (200 °C/0.5 h/160 °C/0.5–8 h)) aging processes. The findings revealed significant microstructural changes due to heat treatment. Homogenization reduced the average grain size of eutectic silicon by 20.5%. The T1 treatment increased the grain size and changed the grain morphology with prolonged aging, negatively impacting the mechanical properties. The T2 and T2L treatments resulted in finer, more uniform grain structures. The T2L treatment produced the finest eutectic silicon and the most uniform grain distribution, indicating the superior potential for mechanical performance. Overall, this study underscores the importance of tailored heat treatment regimes to optimize the microstructure and enhance the structural sensitive properties of Al-Si alloys, benefiting automotive and aerospace industries.

Investigation of microstructure and mechanical properties of Al-Si alloy thin walled cylindrical part fabricated by CMT based WAAM process

Wire Arc Additive Manufacturing (WAAM) represents a major advancement in the production of large-scale metal components. WAAM is recognized for its capacity to produce components with enhanced material properties and structural integrity compared to conventional manufacturing processes. As WAAM involves layer-by-layer fabrication, the resulting components exhibit a higher degree of anisotropy in microstructural and mechanical properties. Additionally, the properties of WAAM components can vary significantly in terms of microstructure and mechanical performance along the build direction of the multi-layered parts. This study investigates the mechanical and microstructural properties of thin-walled cylinder made from Al-Si (Al 4043) alloy using CMT-WAAM. The analysis aims to elucidate the factors contributing to variations in these properties and provide insights into the underlying reasons for observed discrepancies. The micro hardness, tensile strength, and impact strength are analysed at both bottom and top region of the thin walled cylinder. The microhardness, tensile strength, and impact strength of the bottom region are 14.51%, 3.14%, and 12.19% less than those of the top region, respectively, due to the repeated thermal cycles during subsequent layer deposition. Fractographic analysis indicates a ductile fracture mode, characterized by the presence of dimples and microvoid coalescence. Further, the microstructural analysis reveal that top region consists fine grain compared to bottom region of thin-walled cylinder. X-ray Diffraction (XRD) analysis identified secondary phase particles, such as MgSi2 and Al9Si, at the grain boundaries, which was further confirmed by EDS analysis. These microstructural changes and the presence of secondary phases are reasons for the changes in the mechanical properties along build direction.