Al-Si Alloys Research Articles

Influence of Mg and Cu on precipitation behaviors and mechanical properties of Al–Si alloys

Al–8Si-0.5 Mg, Al–8Si–2Cu, and Al–8Si–2Cu-0.5 Mg alloys have been designed in this study, aiming to reveal the influence of Mg and/or Cu additions on microstructures and mechanical properties of Al–Si alloys. Transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and the Kampman-Wagner Numerical (KWN) model have been used to investigate age-hardening behaviors as well as their relation to mechanical properties. Microstructure analysis suggest that β'', θ′ and QP precipitates have formed in peak-aged Al–8Si-0.5 Mg, Al–8Si–2Cu and Al–8Si–2Cu-0.5 Mg alloys, respectively. Notably, the Al–8Si–2Cu-0.5 Mg alloy exhibits faster precipitation kinetics, larger age-hardening response and remarkable thermal stability compared to the other two alloys. Theoretical calculations indicate that the nucleation of QP precipitates is easier than β'' and θ′ precipitates, but the slower diffusivity of Cu limits the growth rate of QP precipitates during the growth stage. Furthermore, the contribution of β'', θ′ and QP precipitates to yield strength of peak-aged Al–Si alloys has been quantified, which shows a significant variation. β'' precipitates in the Al–8Si-0.5 Mg alloy exhibit the highest strengthening effect (∼186.4 MPa), followed by QP precipitates in Al–8Si–2Cu-0.5 Mg (∼160.2 MPa) and θ′ precipitates in the Al–8Si–2Cu alloy (∼13.4 MPa). This work provides valuable insights into the influence of Mg and/or Cu additions on the aging response and mechanical properties of Al–Si alloys, offering a reference for further enhancing the performance of Al–Si alloys.

Design and Optimization of Casting System for Integrated Longitudinal Beam and Tower Package Based on Al-Si Alloy

Design and Optimization of Casting System for Integrated Longitudinal Beam and Tower Package Based on Al-Si Alloy

Effect of Strontium Modification on Microstructure and Mechanical Property Al12SiCuMgNi Alloy in Squeeze Casting

Abstract The Al-Si series alloys, which have excellent fluidity and castability, are the most common aluminum material in the casting industry. However, the coarse eutectic Si phase with laminar morphology leads to the stress concentration of material and has a detrimental effect on the mechanical properties of aluminum alloy components. In this study, the Strontium (Sr) modifier was added to Al12SiCuMgNi alloy and the effect of Sr on microstructure and performance of Al12SiCuMgNi in squeeze casting was investigated. The experimental results show that the eutectic Si phase was well modified to fibrous morphology. Although the yield strength (YS) was leveled, the ultimate tensile strength (UTS) and elongation (EL) of the alloy were obviously enhanced after Sr addition. When the 0.012wt.% Sr was added to Al12SiCuMgNi alloy. The YS, UTS, and EL of alloys were up to 311 MPa, 401 MPa, and 3.4%, respectively. Moreover, the microstructure and performance of Al12SiCuMgNi alloy in the hot forging process were also compared to Al12SiCuMgNi alloy with and without Sr addition in squeeze casting. It is concluded that the Al12SiCuMgNi alloy in hot forging shows higher ductility (4.7%) and lower strength than Al12SiCuMgNi alloy in squeeze casting.

Wire-feeding friction stir welding for large-gap width tolerances

A novel method, named wire-feeding friction stir welding, was proposed for welding large-gap-width joints. Continuous wire feeding and welding systems were designed. AA6082-T6 aluminium alloy plates with a gap width of 2 mm were welded using Al–Si alloy wires as the filler materials. Sound joints were obtained even if the gap width reached over 2/3 thickness of the base materials. Fine microstructures were obtained via dynamic recrystallisation induced by severe plastic deformation. The ultimate tensile strength of the joints reached 253.4 ± 1.3 MPa. The adaptability to working conditions of friction stir welding was improved for long welds of high-speed railway, ship and aircraft.

Effect of the Melt Cooling Rate on the Structural-Phase State of the Al–Si Alloy Doped with Metals

Effect of the Melt Cooling Rate on the Structural-Phase State of the Al–Si Alloy Doped with Metals

Regulation to Ag–Al spikes through silver aluminum paste with Al–Si alloy

It is known that metallization of Ag–Al pastes to boron doped emitter of N-type solar cells will reduce contact resistance, because Al will promote forming Ag–Al spikes, providing conductive channels. However, deeper Ag–Al spikes will exacerbate metal recombination and deteriorate cell performance, thus requiring regulation. It has been reported that adding Si to Ag–Al pastes could effectively limit the formation of Ag–Al spikes, but it will increase grid line resistance and reduce conductivity. Based on this, we prepared new Ag–Al pastes using Al–Si alloys, which effectively regulated Ag–Al spikes and ensured electrical properties. In addition, we comprehensively compared the contact properties of conventional Ag–Al pastes, Ag–Al pastes with added Si, and Al–Si alloy pastes. The results indicated that conventional Ag–Al pastes have lower contact potential barriers and better contact performance, but Ag–Al spikes are difficult to control. Adding Si to Ag–Al pastes effectively limited the formation of spikes, but it will significantly increase potential barriers and deteriorate electrical performance. By contrast, using Al–Si alloys can not only achieve comprehensive regulation of the size and composition of Ag–Al spikes, but also ensure good electrical performance. This study developed Al–Si alloy pastes with great potential for application, which were of great significance for regulation of Ag–Al spikes and the development of advanced Ag–Al pastes.

Analysis of Fe-, Cu-, Mg- and Sr-Based Phases in Al–Si Alloys: Role of P Addition

Analysis of Fe-, Cu-, Mg- and Sr-Based Phases in Al–Si Alloys: Role of P Addition

Scalable synthesis of porous silicon electrodes for lithium-ion batteries via acid etching of atomized Al–Si alloy powders

Scalable synthesis of porous silicon electrodes for lithium-ion batteries via acid etching of atomized Al–Si alloy powders

Effect of thermal treatments on the surface electrical conductivity of AlSi7Mg produced by laser powder bed fusion

In the last years, the production of hypoeutectic Al-Si waveguide components by metal additive manufacturing has gained increasing attention in the telecommunications industry. The performances of waveguide components are influenced primarily by dimensional tolerances, surface electrical conductivity, surface roughness, and dimensional accuracy. Among these properties, electrical conductivity is known to be strongly influenced by the structural and microstructural characteristics of the alloys.In this work, microstructural and structural properties of an hypoeutectic Al-Si alloy, namely the AlSi7Mg alloy, were studied using FESEM, DSC, and XRD to understand how different thermal treatments (stress relieving, T5, and T6) affect the surface electrical conductivity. In the end, the most suitable thermal treatment to be applied to this alloy to maximize its electrical conductivity and, therefore, its appeal for microwave waveguide components is identified.

Optimizing Tribological and Mechanical Properties of Hypereutectic Al–Si Alloys Through Advanced Grain Engineering and Graphene Reinforcement

Optimizing Tribological and Mechanical Properties of Hypereutectic Al–Si Alloys Through Advanced Grain Engineering and Graphene Reinforcement

Assessment of the potential structure and nucleation efficacy of multi-component heterogeneous substrate

In recent years, nucleation of multi-component heterogeneous interface structures has attracted increasing attention due to their excellent grain refinement and anti-poisoning capabilities in Al-Si alloy. In this research, a general methodology was proposed to predict the surface structure and meanwhile evaluate the grain refinement efficacy of the multi-component boride nucleants based on a comprehensive experimental and theoretical study of a novel Al-Si alloy refiner, i.e., Al-3.5 Nb-1 V-1B. By using high-resolution electron microscopy, the (Nb, V)B2 particle with a characteristic “core-shell” surface structure was observed, attributed to V adsorption driven by interfacial energy minimization, validated by ab initio calculations. A general interfacial energy-based model was then proposed which predicts the multi-component boride substrate structure, well consistent with the experimental findings. The nucleation potency of different substrates was analyzed in atomic scale and only if the interfacial atomic vibration was considered together with the nucleation-influencing factors (i.e., the lattice mismatch and the anti Si-poisoning effect), the predicted nucleation potency order can agree well with the experimental results. A thermodynamics-kinetics combined analytic model was summarized by coupling the lattice mismatch parameter, the interfacial Si adsorption energy and the interfacial atomic vibration amplitude, which accurately evaluates the multi-component boride grain refiners for the Al-Si alloys.

Simultaneous integration of anti Si-poisoning and anti-fading properties on an innovative Al grain refiner via Nb-modified TiB2

Si-poisoning and fading effect of grain refiners deteriorate the refining effect of Al-Si alloys (Si≥3 wt%), further worsening the performance of alloys. In this work, an innovative Al-Nb-Ti-B with anti Si-poisoning and anti-fading properties was prepared by introducing synthetic TiB2 into Al-Nb melt. At the cooling rate of 1.4 K/s, the average grain size of Al-7Si alloys inoculated by this Al-Nb-Ti-B was refined to 326.05 μm, 40% reduction compared to 549.06 μm by commercial Al-5Ti-1B. The grain size remained at 421.95 μm even after 120 min holding time. Anti-fading mechanism was investigated by size distribution analysis of TiB2 nucleating particles. Anti Si-poisoning mechanism is attributed to Nb element which accumulates on the (01—10) surface of TiB2 and reduces the lattice misfit between TiB2 and α-Al. Atomic-scale microstructure analysis and first-principles calculations reveal that the Nb enrichment on TiB2 increases the chemical affinity of TiB2/Al interface and decreases the Si adsorption propensity. In brief, appropriate size distribution and unique Nb-rich layer contribute to the excellent grain refinement of TiB2 particles modified by Nb. These findings may shed new light on the realm of innovative aluminum grain refiners.

Modifying the Microstructure and Mechanical Properties of Non-Heat Treated HPDC AlSi10MnMg Foundry Alloy via Incorporation of TiB<sub>2</sub> Particles and Sc

The demand for structural lightweight in a variety of industries, particularly the automobile industry, has driven the development of heat-free die-cast aluminum alloys with excellent properties. Utilizing lightweight materials, such as Al-Si alloys has several benefits, including higher overall performance in automobiles and other industries, increased heat resistance efficiency, decreased emissions, and reduced weight. The purpose of this study is to modify the microstructure and enhance the mechanical properties of high-pressure die-casting (HPDC) AlSi10MnMg foundry alloy by incorporation of TiB2 and Sc without any heat treatment. The results showed that the HPDC process significantly refines the grain structure and AlSiMnFe intermetallic compounds, transforming the eutectic morphology from sharp to rounded, and 93% enhancement in elongation at the optimum content (0.018 wt.%) of TiB2. While the hardness of the alloy was improved by 15.7% with the addition of 0.03wt.% TiB2. TiB2 incorporation refines the grain structure and AlSiMnFe phases, while depressing externally solidified crystals (ESCs). The HPDC process refines Al3Sc phases as well as AlSiMnFe phases while increasing yield strength due to Al3Sc strengthening effects. After 0.5wt.% Sc addition in 0.018wt.% TiB2-AlSi10MnMg alloy, the YS, and EL reached the maximum of 196MPa and 9.93% respectively.

Effect of multi wall carbon nanotubes during semi-solid to solid phase transformation in eutectic Al-Si alloy

The study explores numerically the combined effect of the base metal pouring temperature and MWCNT (multi wall carbon nanotubes) during semi-solid to solid solidification of Al-Si-MWCNT composite material. The semi-solid to solid solidification actually differs significantly both qualitatively and quantitatively from the liquid to solid solidification. During solidification of Al-Si-MWCNT composite material, the melt temperature and the cooling rate play crucial roles in the phase transformations. During liquid to solid solidification, the MWCNT significantly affects the cooling rate, leading to multiple recalescence phenomena, and influences the formation and evolution of the columnar and globular grains. Under the same condition, the MWCNT also impacts the silicon segregation, causing fluctuations in the silicon phases and its redistribution. However, during the semi-solid to solid solidification, it is observed that by decreasing the melt temperature into a semi-solid state, the segregation rate of silicon decreases which enhances more homogeneous CNT distribution. It also increases the globular volume fraction and dominates the columnar growth. Overall, the future trend of semi-solid to solid solidification of Al-Si-MWCNT composite materials lies in optimizing their properties for specific applications, expanding their use across diverse industries, and promoting sustainable manufacturing practices.

Investigation of Modifying Alloying Elements in High-Pressure Injection Casting Eutectic Al-Si Alloys

In the study, the mechanical properties of aluminum alloys produced by the injection molding method, especially using Strontium and Titanium metals, were optimized without being subjected to cold forming. Mechanical tests were applied to the alloys produced by the high-pressure casting technique, and their strength, hardness, and microstructure were examined. Optical and SEM microscopy examinations investigated grain structures. Within the scope of the study, AlTi5B1 master alloy and AlSr10 master alloy were added to the pure AlSi10 (Fe) alloy in 5 different compositions. AlTi5B1 master alloy added to pure AlSi10(Fe) alloy significantly increased the hardness by reducing the grain size. Si modification took place with the addition of AlSr10 master alloy, and it was observed that the obtained weight ratios of 150ppm, 300ppm, and 450ppm Sr increased the hardness proportionally by 2.5 HB each. With the increase in Ti and Sr master alloys added, a significant increase was observed in tensile and yield strengths and % elongation rates. In the compression test, the percentage (%) deformation elongation, the reduction of the grain structure of the material by the added Ti and Sr elements, and the transformation of the eutectic silicon into a spherical structure absorbed the applied Fm force. This led to an increase in strength, and while the permanent deformation elongation decreased as the weight of Ti increased, it was observed that the permanent deformation elongation decreased proportionally with each added amount of 150 ppm Sr. The addition of the Ti element reduced the grain size by shrinking the α-Al dendrites, but it did not affect the eutectic Si.

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.

Characterization of Al-Si Alloy Reinforced with B4C and TiO2 Nanoparticles

Characterization of Al-Si Alloy Reinforced with B4C and TiO2 Nanoparticles

Flexible Janus Black Silicon Photothermal Conversion Membranes for Highly Efficient Solar-Driven Interfacial Water Purification.

Photothermal conversion materials are critical in the development of solar-driven interfacial evaporation techniques; however, achieving a high energy conversion efficiency remains challenging owing to the high cost and instability of light-absorbing materials, in addition to the difficulties of simultaneously improving light absorption while suppressing heat loss. A black silicon (Si) powder with a porous structure was prepared by chemical etching of a low-cost commercial micron-sized Al-Si alloy, and a flexible Janus black Si photothermal conversion membrane was constructed. The partially broken spherical particles and porous structure obtained after etching enhanced the refraction of light from the Si powder, imparting the prepared membrane with an average light absorption rate of 95.95% over the solar spectrum. Evaporation from the membrane increased the intermediate water content and reduced the equivalent evaporation enthalpy. The thermal conduction loss was inhibited through a one-dimensional water transport structure, and the membrane achieved a water evaporation rate of 2.17 kg m-2 h-1 and a photothermal efficiency of 94.95% under 1 sun illumination. Benefiting from the broadband absorption and high photothermal efficiency of black Si powder, surface modification of hydrophobic polydimethylsiloxane, and directional salt-out structure design, the evaporation rate of the Janus black Si membrane-based system in a 10% NaCl solution was maintained >2.10 kg m-2 h-1 after 7 days of continuous evaporation cycles. The removal rate of metal ions from simulated seawater and from practical wastewater containing complex heavy metals reached >99.9%, indicating the promising potential of black Si membrane for application in solar-driven interfacial water purification.

Optimizing Factors affecting gas porosity in GDC of Al-Si (A356) Alloy using Taguchi’s DOE

Aluminium alloys find extensive use in various applications because of its advantage of strength-to-weight ratio,. However, the casting process introduces susceptibility to defects, and managing all parameters proves to be a complex task. Casting rejections often stem from one or more defects, with mold parameters, filling, and solidification processes being key contributors. When the molten metal of the Al-Si (A356) alloy is exposed to the atmosphere in a holding furnace, it develops an oxide layer on its surface. Turbulence in the molten metal leads to the formation of a double oxide layer, also known as bifilms. Gas entrainment occurs due to the turbulent movement of metal, resulting in the entrapment of gas in the molten metal and ultimately causing gas porosity in the final casting. Gas entrapment during the filling process leads to gas porosities during the solidification phase.This study aims to comprehend the factors influencing the formation of gas entrapment during the casting of the aluminium alloy Al-Si (A356). The experimental investigation utilizes Taguchi’s Design of Experiments (DOE) to explore the impacts of parameters such as pouring temperature (PoT), degassing time (DgT), and volume in the holding furnace (VoH) on the formation of gas porosity in casting [8].An experimental setup was created to produce tensile test rods and reduced pressure test (RPT) samples. The results were validated using the mechanical properties of the tensile test samples and the density of the Reduced Pressure Test (RPT) samples. Better the mechanical properties, fewer will be the defects in castings. Taguchi’s DOE is applied to analyse the results. The experimental findings indicate that a pouring temperature at level 1 (710°C), degassing time at level 1 (10 minutes), and volume in the holding furnace at level 1 (>450 kg) yield favourable castings. Confirmatory tests were conducted to validate the results, and they aligned with the experimental data.

Effect of loading conditions on short fatigue crack propagation behaviours in cast Al[sbnd]Si alloys

The effect of loading conditions on short crack propagation behaviours in cast AlSi alloys was investigated by a combination of photo-microscopy monitoring and post mortem analysis. The findings suggest that the path of short cracks is minimally influenced by loading conditions, whereas loading conditions significantly affect the fatigue crack growth rate (FCGR) and its statistical characteristics. Crack closure effect is observed under zero and negative stress ratio conditions. Roughness-induced crack closure occurs due to the coarse grain microstructure of cast AlSi alloys and the Stage-I mode growth of cracks within grains in the microstructural short crack regime. The high level of plasticity around the crack tip under negative stress ratio conditions has a significant impact on FCGR, resulting in a negative crack opening stress. When the stress ratio exceeds approximately 0.3, short cracks exhibit no crack closure. The load-level effect is observed only at high load conditions with negative stress ratios. Finally, a probabilistic short crack growth model was established using a Bayesian linear regression model to analyse the effect of stress ratio on the uncertainty of FCGR. After considering the crack closure effect, the difference in distributions of FCGR model parameters decreases significantly among different stress ratio conditions.