Size Of Si Particles Research Articles

Si anodes via dual strategies of coating Si with a rigid polymer and employing a polymer binder with improved mechanical properties

Si undergoes significant volume change over cycles which degrades the structural integrity and stability of the electrode. This volume change is the primary barrier to the commercialization of Si anodes, and it is more pronounced for Si particle sizes over 150 nm. In this study, a crosslinked polymer binder is developed using poly(acrylic acid-co-acrylamide) (PAAM) with enhanced elasticity compared to the widely used poly(acrylic acid). PAAM is further grafted with boronic acid and dopamine, yielding PAAM-B-D, a binder with improved adhesion due to its 3D crosslinked network. Additionally, 350-nm Si is coated with cyclized polyacrylonitrile (cPAN) and heat-treated to form a conjugated structure. The cPAN-coated Si (cSi) exhibits enhanced conductivity and mechanical stiffness and is used as an active material. The developed Si anode effectively combines cPAN-coated Si with the crosslinked network formed in the PAAM-B-D polymer for enhanced adhesion. The cSi@PAAM-B-D electrode sufficiently maintains its structural integrity and mitigates the Si volume change even with the large-sized 350-nm Si. The cSi@PAAM-B-D exhibits a high initial Coulombic efficiency of 86.5 %, at a Si mass loading of 2 mg cm−2. It also shows a capacity retention of 83.6 % and a high areal capacity of 3 mAh cm−2 after 50 cycles.

High‐Performance Yolk‐Shell Structured Silicon‐Carbon Composite Anode Preparation via One‐Step Gas‐Phase Deposition and Etching Technique

AbstractFor producing high‐capacity silicon (Si) anodes, a combined gas‐phase deposition and etching technique is developed to construct yolk‐shell structured silicon‐carbon composites. As a novel etching agent in battery field, NF3 is applied to selectively etch Si to tailor the architecture. Si particles as self‐sacrificed precursor have no need to build artificial or complex templates in advance, thereby greatly simplifying fabrication process and showcasing practicality. As a result, yolk‐shell structured silicon‐carbon composites are successfully fabricated in a single step. Sufficient buffer space between Si and carbon layer accommodates the significant expansion of Si during lithiation, preventing fracture of the carbon layer, which greatly improves service life of Si‐based anodes. Moreover, the refined particle size of Si and abundant pores in inner Si cores enhance the lithiation and de‐lithiation kinetic. Even with a high Si loading of 3.9 mg cm−2, the produced anode exhibits a superior areal capacity of 16.3 mAh cm−2 at 0.2 mA cm−2. Furthermore, at a high current density of 4 A g−1, it demonstrates an excellent capacity of 1114 mAh g−1 after 1000 cycles with a capacity retention of 96.3%. Additionally, with pre‐lithiation, it is successfully paired with an iron trifluoride cathode to construct high‐energy lithium‐ion batteries.

Comparative effects of micron-sized silicon sources and Si nanoparticles on growth, defense system and cadmium accumulation in wheat (Triticum aestivum L.) cultivated in Cd contaminated soil

Elevated levels of cadmium (Cd) in soils posesignificant challenges to global agricultural crop production. The potential of silicon (Si) nanoparticles (NPs) and biogenic Si sources of different sizes to mitigate Cd stress in wheat remains largely unexplored. A pot experiment was conducted to evaluate the effectiveness of various sizes of biogenic Si sources: rice husk biochar (RHB), sugarcane bagasse (SB), and rice straw (RS); categorized by particle size (<150 μm, 150–250 μm, and 250–1680 μm, denoted as S1, S2, and S3, respectively), and Si NPs on wheat growth and Cd accumulation. The application of RHB (<150 μm) significantly increased plant height (105 %), spike length (94 %), shoot dry weight (93 %), root dry weight (83 %), and grain weight (89 %) compared to the control. The RHBS1 treatment delivered the greatest reduction in the bioavailable fraction of soil Cd (-74 %), as well as Cd levels in roots (-85 %), shoots (-93 %), and grains (-97 %) compared to the polluted control. Additionally, RHB (<150 μm) showed the highest increase in antioxidant enzyme activities compared to the Cd-spiked treatment. Interestingly, the various biogenic Si sources have the potential to mitigate Cd stress in wheat plants. Further research is required to understand the underlying mechanisms and to investigate the effectiveness of different biogenic Si sources and particle sizes in alleviating Cd stress in crops.

Impact of Binder Content and Type on the Electrochemical Performance of Silicon Anode Materials.

Binders are crucial for stabilizing the cycling performance of silicon (Si) materials by preventing Si particle pulverization during lithiation and delithiation. Poly(acrylic acid) (PAA) and carboxymethyl cellulose (CMC) are the two most studied binders for Si electrodes, with PAA being an elastic polymer and CMC a rigid polymer. Starting with the elastic PAA, in this work the impact of binder content on the cycling performance of Si electrodes is studied. It is found that regardless of Si particle size, there is an optimal binder content between 20 % and 25 % for the cycling stability of Si electrodes. On the other hand, the rigid CMC binder results in lower capacity and faster capacity fading for Si electrodes compared with the elastic PAA. AC-impedance analysis reveals that the lower capacity is due to higher grain boundary resistance (Rgb) in CMC-coated electrodes, leading to high charge-transfer resistance (Rct) and increased polarization. This high polarization triggers premature termination during the discharging process (i. e., the lithiation) of Li/Si cells, underutilizing the Si active material. Additionally, the rapid capacity fading of CMC-coated electrodes is attributed to the rigid binder's inferior ability to prevent Si particle pulverization.

Enhancing performance: Pre-processing heat treatment's influence on fast multiple rotation rolling of friction-surfaced Al-16Si-4Cu alloy

This study investigated the influence of pre-processing heat treatment on the fast-multiple rotation rolling (FMRR) of Al-16Si-4Cu alloy friction-surfaced onto the AA1050 aluminum substrate. Results showed that applying solid solution treatment before both the friction surfacing and FMRR processes yielded the thinnest coating thickness (1.4 ± 0.2 mm). Moreover, using a solid solution-treated Al-16Si-4Cu alloy rod resulted in the smallest average size of Si particles (4.2 ± 0.1 μm) in the FMRR-treated layer. Additionally, the most uniform distribution and smallest size of Al2Cu precipitates in the FMRR-treated layer were achieved by subjecting the alloy to solid solution treatment prior to both FMRR and friction surfacing. Notably, solid solution treatment preceding both FMRR and friction surfacing processes produced maximum nano-hardness (10.42 ± 0.54 GPa), shear strength (174.32 ± 9.21 MPa), and elastic modulus (221.03 ± 0.54 GPa) in the clad layer. Furthermore, pre-processing with solid solution heat treatment led to the lowest wear rate of the clad layer, exhibiting a reduction of 74.47 % compared to the AA1050 substrate.

Effect of fast multiple rotation rolling on friction surfaced Al[sbnd]Si[sbnd]Cu alloy

In this study, the impact of four linear speeds (75, 95, 115, and 135 mm/min) during fast-multiple rotation rolling (FMRR) on the A390 coating applied via friction surfacing (FS) on the AA1050 substrate was investigated. The microstructure, mechanical properties, and wear resistance were examined using optical microscopy, scanning electron microscopy, electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), nanoindentation tests, microhardness tests, and pin-on-disc tests. Results showed that as the linear speed increased to 135 mm/min, the FMRR-treated layer became 48.6 % thinner. At a linear speed of 135 mm/min, the grain size reduced to 1.24 ± 0.15 μm, and the sizes of Al2Cu and Si particles decreased to 0.51 ± 0.02 μm and 3.45 ± 0.11 μm, respectively. The nano-hardness and Young's modulus increased to 9.11 GPa and 218.9 GPa, respectively. Moreover, the wear rate decreased by 43.53 % compared to the consumable rod and by 65.96 % compared to the AA1050 substrate at a linear speed of 135 mm/min. EBSD results indicated the presence of recrystallization and shear texture components in the FMRR-treated layer. TEM analysis confirmed the presence of nanometer-sized Si particles (<10 nm) and grains (100–500 nm) in the FMRR-processed layer.

Si particle size blends to improve cycling performance as negative electrode for all-solid-state lithium-ion battery

Silicon negative electrodes dramatically increase the energy density of lithium-ion batteries (LIBs), but there are still many challenges in their practical application due to the limited cycle performance of conventional liquid electrolyte systems. In this study, we clarified that the use of an inorganic solid electrolyte improves the cycle performance of the LIB with the Si negative electrode and the size of Si particles influenced the properties of the all-solid-state LIB. The all-solid-state LIB using micro-sized silicon (mSi) particles as the negative electrode active material showed a large initial discharge capacity (2400 mAh g-1), but the discharge capacity decreased as charge/discharge cycles increased. In contrast, the all-solid-state LIB using nano-sized silicon (nSi) particles showed a low initial discharge capacity (1000 mAh g-1), but the discharge capacity increased for the initial 20 charge/discharge cycles. The cross-sectional images analyzed by scanning electron microscopy showed that for mSi particles, cracks and voids occurred due to volumetric changes during charging and discharging, interrupting the flow path of ions and electrons, whereas for nSi particles, the contact with the solid electrolyte and conductive material was improved. Moreover, the all-solid-state LIB using the negative electrode of nSi: mSi = 7: 3 (mass ratio) showed higher initial discharge capacity and longer cycle performance than that using mSi and nSi.

Are Sulfide‐Based Solid‐State Electrolytes the Best Pair for Si Anodes in Li‐Ion Batteries?

AbstractThe integration of Si‐based anodes within sulfide‐based solid electrolyte (SSE) Li‐ion batteries (LIB) has emerged as a promising avenue of research and development, attracting increasing interest in recent years. This work comprehensively examines the latest research directions and major strides in this field. It covers the key advances in the design and engineering of nano‐ and micro‐structured Si anode architectures, and strategies of surface modification. Additionally, it explores the impacts of external pressure, the role of binders and conductive additives, and the implications of varying Si particle size. Beyond providing a detailed account of the evolution of Si anodes within SSE LIBs, this work also identifies critical research challenges that urgently need addressing. These include the electrochemical‐mechanical evolution behavior and failure mechanism of Si anodes in SSE LIBs, strategies for structural and interface modifications, methods for preparing Si electrodes, advancements in high‐performance SSEs, and the development of scalable technologies for SSE thin films. Moreover, it discusses high‐energy cathodes tailored for Si‐based SSE LIBs. The identified research priorities are set to offer crucial guidance and insights, supporting the ongoing investigations and innovations in this dynamic area of research.

A new study on the effects of clay nanoparticles on the corrosion performance of Al-Si-Cu matrix composites in both acidic and alkaline solutions

In this paper, the influence of clay nanoparticles on the corrosion properties of the Al-Si-Cu matrix was investigated. The nanocomposite fabricating method was stir-casting when stirring times and temperatures were variables to change nanocomposite characteristics. Several corrosion tests were performed to examine the relationship between the microstructure and the degradation mechanism of various fabricated nanocomposites. Tafel polarization measurements indicated a lower corrosion rate for all nanocomposites compared to the Al-Si-Cu matrix in 0.1 M NaOH solution. The reduction range was 23.6–79.0% based on the smaller size of Si precipitates. In this situation, the interconnection of surface pores was lowest. However, electrochemical impedance spectroscopy (EIS) results showed that nanocomposite impedance would be increased up to 99.7% in comparison to the matrix without clay nanoparticles in 1 M HCl solution when the stirring temperature was 750 °C. EIS calculation also displayed that an increase (about 17.1–50.8%) in the nanocomposite resistance would be achieved when the stirring time was 2 min in 0.04 H2SO4 solution. The reason could be attributed to the larger size of Si particles since coarse precipitates were more effective agents to act as barriers for anodic dissolution of the lower layer of the Al-Si-Cu matrix when Tafel polarization tests demonstrated that the anodic reaction controlled the corrosion rate of the aluminum matrix.

Silicon Solid State Battery: The Solid‐State Compatibility, Particle Size, and Carbon Compositing for High Energy Density

AbstractSolid‐state battery research has gained significant attention due to their inherent safety and high energy density. Silicon anodes have been promoted for their advantageous characteristics, including high volumetric capacity, low lithiation potential, high theoretical and specific gravimetric capacity, and the absence of lethal dendritic growth. Addressing concerns such as low conductivity, pulverization, fracture, dense solid electrolyte interface layer, and low coulombic efficiency has substantially improved the use of silicon electrodes in solid‐state batteries. Researchers have explored carbon additions, solid electrolyte suitability for Si anodes, pressure optimization, and particle size effects (nano/micro) to enhance energy density. Recent studies have investigated the conductivity mechanism, stack pressure, and anode‐solid electrolyte compatibility to improve energy density. Micro‐ and nano‐sized silicon have attracted attention in carbon‐based composites due to their exceptional conductivity, uniform distribution, efficient electron migration, and diffusion channels. The development of solid‐state batteries with high energy density, safety, and extended lifespan has been a major focus. This review sheds light on significant insights and strategic approaches for researchers working on solid‐state silicon‐based systems to overcome existing challenges.

Improving the comprehensive mechanical property of the AlSi10Mg alloy via parameter adaptation of selective laser melting and heat treatment

In this work, the AlSi10Mg alloys with distinct molten pool structures, namely fish-scale and lamellar, were fabricated by using selective laser melting (SLM) technology. The effects of solid solution temperature on the microstructural evolution and mechanical properties of the two types of alloys were systematically investigated. The relationship among initial structure, heat treatment and mechanical properties was revealed. The experimental results showed that for the alloy with fish-scale structure, Si diffused more easily after solid solution treatment due to the finer eutectic network, resulting in a larger Si particle size. At 510 °C, the nano Si particles in the fish-scale sample basically disappeared, but a small amount of nano Si particles still existed in the lamellar sample, leading to a bimodal distribution in the Si particle size. Different sizes and distributions of Si particles present different strengthening mechanisms and affect the nucleation and growth of recrystallized grains in the α-Al matrix, leading to significant differences in mechanical properties. The strength of the lamellar sample decreased with increasing the temperature, and the abnormally growth of grains could be found after being treated at 510 °C, resulting in a poor mechanical property. The strength of fish-scale sample first decreased and then increased with the increase of solid solution temperature. When the alloy with fish-scale structure was solid solution treated at 510 °C, Si particles could promote the nucleation of recrystallized grains but hinder their growth, and the ultimate tensile strength decreased from 478.8 MPa of SLMed state to 393.4 MPa, a reduction of 17.8%, while the elongation increased from 7% to 21%, an increase of 300%, showing an excellent overall mechanical property. Therefore, the present study demonstrates that adjusting the SLMed molten pool structure and heat treatment parameters is necessary to obtain a good combination of microstructure and mechanical property.

Studying Degradation of Micro- and Nano-Scale Silicon in Si/ Rgo-Anode Materials for Lithium-Ion Batteries – Towards a Fair Comparison

An attractive approach to increase the Li+-storage capacity of anode materials in Lithium-ion batteries (LiBs), is to replace or combine the routinely-applied graphite (372 mAh g-1) with higher-capacity materials. Among others, silicon (Si) with a theoretical capacity of 3579 mAh g-1 is a promising candidate [1]. Silicon is not yet been used as an anode material in its pure form, due to its low conductivity and volume increase of up to 300 % during lithiation. This two-step expansion (1st: Si + 2 Li+ + 2 e- → SiLi2.0; 2nd: SiLi2.0 + 1.5 Li+ + 1.5 e- → SiLi3.5) is a source of mechanical stress that can ultimately lead to battery failure. Furthermore, the initial lithiation of crystalline silicon (c-Si + 3.5 Li+ + 3.5 e- → SiLi3.5) causes an amorphization of the pristine crystalline lattice. This structural change causes further degradation of the material, which can hardly be avoided [2].The main degradation mechanisms resulting from expansion and amorphization are I) The uncontrolled formation of a passivation layer due to the cyclic volume change taking place during (de-)lithiation, which leads to a continuous break-up and reformation of the solid electrolyte interphase (SEI). II) The pulverization of particles resulting in mechanical stress and the electrical isolation of particles or particle fragments delaminating from the electrode [3]. The first mechanism discussed is more dominant for nanometer scaled particles (nm-Si), while the second mechanism occurs mostly for particles in the micrometer range (µm-Si).Our approach combines, nm- or µm-sized Si particles with different matrix materials. By incorporating the particles into an either graphitic or soft carbon-like support, we aim to increase the conductivity of the electrode material and gain additional buffer space thereby reducing interparticle mechanical stress [4]. On the one hand, the systems of carbon-based anode materials are already well understood in terms of electrode composition, processing parameters, electrolyte compatibility, formation of a stable SEI and the resulting high cycling stability. On the other hand, the observed degradation mechanisms will occur with different predominance in different Si/C composites depending on the Si particle size and the chosen carbon matrix. However, the latter is not completely understood. We will address these issues by comparing different Si/C-composites consisting of nm-Si-particles or µm-Si particles in a reduced graphite oxide (rGO) matrix and in a graphite-matrix.Electrochemical methods, such as galvanostatic cycling, impedance spectroscopy and dq/dU-analysis in 2- and 3-electrode setups, were coupled with optical and spectroscopical techniques (e.g. XRD, FTIR, SEM) to trace back the electrochemically measurable degradation of the electrode to structural changes during formation and cycling. Particular attention was paid to the localization and analysis of defect areas with increased degradation by correlating the optical and spectroscopical results data with the lithiation and delithiation processes. Considering the different SoC levels, we can identify the ongoing aging of the different electrode materials. Based on this, we propose the use of soft carbon-like structures such as rGO as a matrix material for Si/C composites due to its higher cycling stability under the investigated conditions.

Operando Investigation of Silicon Anodes During Electrochemical Cycling in Li-ion Batteries.

Silicon (Si) is recognized as a promising anode material for next-generation anodes due to its high capacity. However, large volume expansion and active particle pulverization during cycling rapidly deteriorate the battery performance. The relationship between Si anode particle size and particle pulverization, and the structure evolution of Si particles during cycling is not well understood. In this study, a quantitative, time-resolved "operando" small angle X-ray scattering (SAXS) investigation into the morphological change of unwrapped and reduced graphene oxide (rGO) wrapped Si nanoparticles (Si@rGO) is conducted with respect to the operating voltage. The results provide a clear picture of Si particle size change and the role of nonrigid rGO in mitigating Si volume expansion and pulverization. Further, this study demonstrates the advantage of "operando" SAXS in electrochemical environments as compared to other approaches.

Boosting the grain refinement of commercial Al alloys by compound addition of Sc

For decades, Al–Ti–B has been widely used for refining commercial Al alloys. However, the addition of Al–Ti–B master alloys to recycled Al alloys suffers from Si-poisoning and cannot achieve desired refinement and thus final strength-ductility. In this study, a novel grain refiner made of Al–Ti–B-Sc has been developed and its application in refining recycled Al–Si–Cu alloys has been quantified using X-ray computed tomography (XCT). It has been found that the new Al–5Ti–1B-0.8Sc master alloy exceed the performance of Al–5Ti–1B in three aspects: (1) formation of Al3(Sc,Ti) heterogeneous nucleation particles other than Al3Ti; (2) dispersing TiB2 by forming TiB2/Al3(Sc,Ti) clusters and increasing Al melt viscosity; (3) reducing the specific surface area of Al3Ti to improve its high-temperature stability. Surprisingly, the compound addition of Sc has been found to further reduce the grain and Si particle size due to accelerated kinetics of α-Al nucleation and diminished Si poisoning. Therefore, this study proposes not only a new master alloy but also a new grain refinement method, which can effectively increase the tensile strength and elongation of recycled Al alloys up to 433.2 ± 10.5 MPa and 3.0 ± 0.1 %, respectively.

Investigation on the properties of anodic oxides grown on aluminium-silicon alloys irradiated by pulsed electron beam

Al-Si alloys are among the most common aluminium based materials for cast products due to theirhigh strength-to-weight ratio, excellent processability and relatively low cost. The presence of Si inthe molten Al phase improves the castability and decreases the solidification shrinkage. Hard anodicoxidation is largely employed to improve their surface mechanical properties and corrosion resistance.However, the presence of high Si contents (&gt; 3%) and the size of Si particles in the alloy makethe process challenging or even not possible. The surface pretreatment of Al-Si alloys with intensepulsed electron beams (EB) can effectively overcome the aforementioned limitations. Electron beamsources can be employed to reduce Si content and to refine and disperse Si particles, and effectivelycreate an Al substrate that is more prone to oxidization. In the present work, two electron beamunits were used, RITM-SP and SOLO, to modify the surface properties of hypoeutectic, eutectic andhypereutectic Al-Si alloys, by investigating the effect of energy density and number of pulses. Theelectron beam treated substrates were hard anodized and characterized in term of microstructure,elemental distribution, corrosion resistance and surface mechanical properties.

Engineering electrode–electrolyte interface for ultrastable Si-based solid-state batteries

Due to the plentiful supply and extremely high theoretical capacity, Silicon (Si) is acknowledged as a prospective anode material for solid-state batteries with high-energy. Nonetheless, the substantial increase in size of Si particles during cycling causes an unsteady interface, leading to a reduced initial coulombic efficiency (ICE) and inferior cycle longevity. To address this issue, we created a strong layer by applying a solid electrolyte (Li6.4La3Zr1.4Ta0.6O12, LLZTO) with excellent lithium-ion conductivity onto the Si electrode's exterior. The LLZTO coating forms a stable interface between the electrode and electrolyte by utilizing chemical bond cooperation between polyvinyl alcohol (PVA) binder in the LLZTO coating and polyacrylic acid (PAA) binder in the Si electrode. This guarantees excellent interface stability and rapid movement of lithium ions at the interface between the electrode and electrolyte. The Si@LLZTO electrode demonstrates excellent performance, achieving an ultrahigh ICE of 90 %. After 200 cycles, the composite electrode exhibits an outstanding capacity retention of 1363 mAh g−1 at a current density of 1 A g−1. Furthermore, when assembled into a solid-state battery, it exhibits outstanding cycling stability with remarkable capacity retention (386 mAh g−1) over 1000 cycles at 1.2 A g−1.

Persistent Homology Analysis of the Microstructure of Laser-Powder-Bed-Fused Al-12Si Alloy.

The laser powder bed fusion (L-PBF) process provides the cellular microstructure (primary α phase surrounded by a eutectic Si network) inside hypo-eutectic Al-Si alloys. The microstructure changes to the particle-dispersed microstructure with heat treatments at around 500 °C. The microstructural change leads to a significant reduction in the tensile strength. However, the microstructural descriptors representing the cellular and particle-dispersed microstructures have not been established, resulting in difficulty in terms of discussion regarding the structure-property relationship. In this study, an attempt was made to analyze the microstructure in L-PBF-built and subsequently heat-treated Al-12Si (mass%) alloys using the persistent homology, which can analyze the spatial distributions and connections of secondary phases. The zero-dimensional persistent homology revealed that the spacing between adjacent Si particles was independent of Si particle size in the as-built alloy, whereas fewer Si particles existed near large Si particles in the heat-treated alloy. Furthermore, the first principal component of a one-dimensional persistent homology diagram would represent the microstructural characteristics from cellular to particle-dispersed morphology. These microstructural descriptors were strongly correlated with the tensile and yield strengths. This study provides a new insight into the microstructural indices describing unique microstructures in L-PBF-built alloys.

Synergistic Effect of Strontium and Melt Quenching on the Solidification Microstructure of Hypereutectic Al-Si Alloys.

The synergistic effect between strontium (Sr) and melt quenching on the solidified microstructure of hypereutectic Al-Si alloys was investigated by optical and scanning electron microscopy. The results indicate that melt quenching can suppress the growth of primary Si particles in the solidified structure of the hypereutectic Al-Si alloy, resulting in a significant decrease of in the average size of primary Si particles in Al-(18~22)Si alloys from 30.35~66.31 μm to 15.13~34.63 μm. The synergistic effect between Sr and melt quenching can further inhibit the precipitation of primary Si particles in the Al-18Si alloy. After the addition of Sr to Al-18Si alloy and undergoing melt quenching, the area fraction of primary Si clearly decreases. When the added amount of Sr increases from 0.1 wt.% to 0.5 wt.%, the area fraction of primary Si decreases from 1.13% to 0.16%. With 0.5 wt.% Sr in the tested alloy, the inhibiting effect on primary Si precipitation was significantly improved. Research has shown that the cooling rate has a significant impact on the solidified structure of the melt-quenched Al-18Si-0.5Sr alloy. There exists no primary Si in solidified structures on the area of 1/8R and 1/4R from the surface of the round bar sample, but the area fraction of primary Si increases, respectively, to 1.97% and 12.48% on the area of 1/2R and R from the surface. The higher the cooling rate, the higher the inhibitory effect on the primary Si precipitation in the Al-18Si-0.5Sr alloy.

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.

Effects of Mg content on microstructure, mechanical properties and fracture behavior of wrought Al–8Si–(

In this paper, the effects of the Mg content on the microstructure, mechanical properties and fracture behavior of wrought Al–8Si–(<0.01–1.32)Mg (mass fraction, %) alloy sheets in T6 temper were systematically studied by OM, SEM/EDS, EBSD, LSCM, DSC, TEM and tensile tests. The results show that the size of Si particles decreased slightly with the increase of Mg content, and the recrystallized grain size of experimental alloy sheets was refined from about 16 µm to about 11 µm. The size of β" phases did not change obviously, but its volume fraction increased gradually and then became stable. When Mg content was 1.32%, there were many associated aggregation areas of Mg2Si particles and Si particles in alloy sheet. In addition, the strength of experimental alloy sheets showed an initial increase followed by a slight decrease as the Mg content increased, while the elongation gradually decreased. The finite element model accurately predicted the yield strength of Al–8Si–(<0.01–1.32)Mg alloy sheets in T6 temper, and the model was able to quantify the contribution of various strengthening mechanisms to the yield strength of the alloy sheets. The predicted results were in good agreement with the actual measured results. The tensile fracture mode of Al–8Si alloy sheet was ductile fracture. When Mg content was greater than 0.51%, the fracture pattern of the sheets comprised a combination of ductile and brittle fractures. With the increase of Mg content, the number of dimples in experimental alloy sheets increased slightly, the depth gradually became shallow and the size slightly decreased. Meanwhile, most secondary cracks on the surface of the Al–8Si alloy sheets after tensile fracture bypassed the Si particles and a few sheared the Si particles. With the Mg content gradually increasing to 0.78%, the number of Si particles sheared by secondary cracks gradually increased. However, When Mg content was 1.32%, the intergranular fracture phenomenon of Al–8Si–1.32Mg in T6 temper was weakened or even disappeared. There were multiple particles embedded in the same dimples in the tensile fracture. The particles in the associated aggregation areas were more easily broken.