Al-12Si Alloy Research Articles

Microstructure, mechanical, and corrosion properties of Al–10Si and Al–10Si–2Cu alloys with different La contents

The effects of La content on the microstructure, mechanical properties, and corrosion behavior of Al–10Si and Al–10Si–2Cu alloys were studied. With the addition of a certain amount of La to these alloys, the grain refinement effects of α-Al were confirmed to be 16.4% and 18.6%, respectively. In addition, precipitates of the Al–Si–La and Si–Cu–La phases were formed in the form of a core-shell structure with the addition of La. Owing to the grain refinement and precipitation strengthening effects, the hardness was improved by 5% and 10.9%, respectively. The Al–10Si–2Cu alloy was found to have better mechanical properties than the Al–10Si alloy because the dispersibility of Cu-related precipitation phases could be improved by the attraction with La during Cu precipitation. The addition of La also improved the corrosion resistance. Both Al–Si and Al–Si–Cu alloys showed improved corrosion resistance owing to the grain refinement effect, and the improved effect was greater in Al–Si–Cu alloys. This is because the growth of Al2Cu, which is the main cause of galvanic corrosion, was suppressed, attributed to the formation of a Si–Cu–La phase by the addition of La instead of Al2Cu. The potential analysis showed that the potential difference between the newly formed Si–Cu–La phase and the α-Al phase was found to be 21% lower than the potential difference between the α-Al and Al2Cu phases. These results confirmed that the corrosion resistance improvement effect of the Al–Si–Cu alloy was greater than that of the Al–Si alloy with the addition of La.

Effects of Temperature on the Fatigue Characteristics of the Bond Zone between the Al-12Si/ABOw Composites and Al-12Si Alloys

Effects of Temperature on the Fatigue Characteristics of the Bond Zone between the Al-12Si/ABOw Composites and Al-12Si Alloys

Multi-scale investigation of A356 alloy with trace Ce addition processed by laser surface remelting

Laser surface remelting (LSR) has shown great application potential in Al-Si alloy parts (e.g., surface strengthening, surface repairing). However, the microstructural details and properties of LSR-treated hypoeutectic Al-Si alloy remains to be investigated. In this work, the microstructure of an Al-7Si alloy with adding 0.05 wt% Ce fabricated by LSR was studied through multi-scale characterization. Three regions with distinct morphologies after LSR were obtained: i) the remelting zone (RMZ) including an equiaxed grain region and a columnar to equiaxed transition (CET) region; ii) the heat-affected zone (HAZ) with segregation of Si; iii) substrate zone (SZ). Nanoscale eutectic Si particles were observed in RMZ and HAZ. Moreover, it is confirmed for the first time that the Ce atom can absorb on the {111}Si planes and leads to high density of twins and stacking faults. After LSR, the increased microhardness of RMZ is mainly attributed to the precipitation and dislocation strengthening. By further T6 heat treatment, the microhardness of RMZ increases to 126 HV. Dispersed small Si particles decrease the critical stress of crack propagation. Additionally, the high density of twins, stacking faults and Al-rich clusters within Si particle plays a significant role in toughness improvement.

Effect of heat treatment and ageing on microstructure for hypoeutectic Al-7Si alloy and hybrid metal matrix composites

In the present investigation on fabrication and microstructure of aluminium based hybrid composites. A356 based aluminium matrix material with varying reinforcement percentage from 0 to 9 wt. % in steps of 3 wt. % silicon carbide (SiCp) and fixed quantity of 3 wt. % of graphite (Gr) particles were used in fabrication. The specimens were fabricated by stir-cast method. Heat treatment was carried out for the cast specimen at 540oC for 12 hours and further ageing was carried out at 155ºC for 3, 6, 9 and 12 hours durations. The specimen after heat treatment and ageing were quenched in water at 60oC. The prepared specimens (ascast and aged) were examined using optical microscope to know the particle distribution in the matrix. Hardness and tensile were carried out for as-cast and aged specimen. The results were compared with as-cast and aged specimens. There was a significant improvement in hardness and tensile properties due to increase in the weight percentage of SiCp. The specimen A356-9SiCp-3Gr aged at 9 hrs showed improved hardness, and tensile when compared to other tested specimen. The presence of reinforcements (SiCp and Gr) significantly affects the solid state transition kinetics that improves the properties of composites. The presences of reinforcements in the specimens are evident from the electron dispersive spectroscopy (EDS) analysis.

Effect of Cooling Rate on Nano-Eutectic Formation in Laser Surface Remelted and Rare Earth Modified Hypereutectic Al-20Si Alloys

Laser Surface Remelting (LSR) was applied to arc-melted Al-20Si-0.2Sr, Al-20Si-0.2Ce, and Al-20Si hypereutectic alloys to refine microstructures. Experiments revealed that microstructures in the melt pool varied from fully eutectic to a mixture of Al dendrites and inter-dendritic eutectic. We calculated cooling rates using the Eagar-Tsai model and correlated cooling rates with characteristic microstructures, revealing that a cooling rate on the order of 104 K/s could lead to maximized fully eutectic microstructure morphology. Due to rapid solidification, the Si composition in the LSR eutectic was measured at 18.2 wt.%, higher than the equilibrium eutectic composition of 12.6 wt.%Si. Compared to Al-20Si, Ce addition had no significant effect on the volume fraction of the fully eutectic structure but refined Si fibers to approximately 30 nm in diameter. Sr addition did not further refine the diameter of eutectic Si fibers compared to Al-20Si but increased the volume fraction of the fully eutectic microstructure morphology. The refinement ratio (φ) of the Si fiber diameter from the bottom of the melt pool to the surface for the three alloys was similar, at around 28%. The established correlation between the cooling rate and the size and morphology of the microstructure within the melt pool will enable tailoring of the microstructure in laser-processed as well as deposited alloys for high strength and plasticity.

Effect of Powder Characteristic and Aging Treatment on the Corrosion Behavior of Selective Laser Melted Al-20Si Alloy

Effect of Powder Characteristic and Aging Treatment on the Corrosion Behavior of Selective Laser Melted Al-20Si Alloy

On the Effect of the Oxidative Milling of Matrix Powder on the Structure and Properties of Aluminum Foam Based on the Al–12Si Alloy

On the Effect of the Oxidative Milling of Matrix Powder on the Structure and Properties of Aluminum Foam Based on the Al–12Si Alloy

Manufacturing of high-toughness Al–Si alloy by rolling and friction stir processing: Effect of traverse speed

In this work, the influence of traverse speed on the microstructural evolution and mechanical behavior of Al–7Si alloy fabricated by cold rolling and friction stir processing (FSP) was studied. After the FSP, the needle-shaped silicon and Fe-rich phases were modified to fine particles with a low aspect ratio and high sphericity, and porosity was eliminated. The FSPed samples revealed a uniform dispersion of Si and Fe-rich particles in the aluminum matrix. With the increment of the traverse speed, the average size and sphericity of the Si particles were reduced, while the aspect ratio was increased. The peaks of α-Al, Si, Al 4 FeSi 2 , and Al 5 FeSi phases were observed in all samples, however, the Mg 2 Si peak was not visible due to its low content. With increasing the traverse speed, the peak shifting and lattice strain were decreased due to decreasing the degree of plastic deformation. The as-cast sample had an average hardness higher than the FSPed samples owing to the presence of large second phases. By performing the FSP, the tensile properties were significantly improved owing to the refinement, spheroidization, and uniform distribution of particles. Increasing the tool traverse speed up to 120 mm/min enhanced the strength of the FSPed samples because of decreasing the size of silicon and Fe-rich particles. Further increment of the traverse speed led to a decrease in the strength owing to the presence of cavities. The best strength-ductility belongs to the traverse speed of 120 mm/min which resulted in the highest toughness (57.9 J/cm 3 ). The ductile fracture was the dominant feature on the fracture surface of all FSPed samples.

Design and preparation of aluminum alloy with high thermal conductivity based on CALPHAD and first-principles calculation

To obtain the aluminum alloy with high thermal and mechanical properties, the effects of alloying elements and the second phases on the thermal conductivity of Al alloys were investigated by CALPHAD and first-principles calculation, respectively. The properties of the second phases, including Young’s modulus, Poisson’s ratio and minimum thermal conductivity, were systematically studied. Results show that the ranking order of the effects of the alloying elements on the thermal conductivity is Mg>Cu>Fe>Si, and for Al-12Si alloys, the mathematical model of the relationship between the alloying elements and the thermal conductivity can be expressed as λ=ax2-bx+c when the second phase precipitates in the matrix. All kinds of ternary phases of Al-Fe-Si have higher deformation resistance, rigidity, theoretical hardness, Debye temperature and thermal conductivity than the other phases which possibly exist in the Al-12Si alloys. Based on the guidance of CALPHAD and first-principles calculation, the optimized chemical composition of Al alloy with high conductivity is Al-11.5Si-0.4Fe-0.2Mg (wt.%) with a thermal conductivity of 137.50 Wm−1·K−1 and a hardness of 81.3 HBW.

Evaluation of microstructure and mechanical properties of M-SIMA processed Al–7Si alloy

In this research article, the effect of the strain-induced melt activation (SIMA) process on the microstructure and mechanical properties of the Al–7Si alloy has been investigated. The morphology of α-Al grains is changed from dendritic to fine spherical and flaky type eutectic Si to a fine fibrous eutectic Si after the modified strain-induced melt activation (M-SIMA) process. The intermetallic compounds are refined and distributed uniformly throughout the matrix after the M-SIMA process. The mechanical properties have been improved due to fine spherical grain formation with refined eutectic Si. A high tensile strength (UTS: 204 MPa) with a remarkable improvement in ductility (El: 30%) is achieved after the M-SIMA process at 585°C for 30 min in comparison to the as-cast Al–7Si alloy (UTS: 117 MPa, El: 16%).

Effect of Strain Induced Melt Activation Process on the Microstructure and Mechanical Properties of Al-5Ti-1B Treated Al-7Si Alloy

Effect of Strain Induced Melt Activation Process on the Microstructure and Mechanical Properties of Al-5Ti-1B Treated Al-7Si Alloy

Influence of Modification on Flow Stress Behavior and Corrosive Properties of a Hypoeutectic Al-Si Alloy

The flow stress behavior and corrosive properties of Al-7Si alloy were studied by thermal compression test, electrochemical test, and electron probe microanalysis. The influences of temperatures, strain rates, strains, and morphology of Si particles on stress-strain curves of Al-7Si alloy were analyzed. The peak stress of unmodified-Al-7Si alloy is higher than that of Sr-modified-Al-7Si alloy at the same deformation conditions, and the phenomenon is obviously relevant to the distribution and morphology of Si particles. The morphology of Si particles of unmodified-undeformed-Al-7Si alloy is a typical thick layer, and that of unmodified-deformed-Al-7Si alloy is broken into relatively small particles and the distribution is relatively even in homogeneous deformation zone II. The distribution of Si particles in Sr-modified-deformed-Al-7Si alloy is obviously more even than undeformed alloy. The effect of a small deformation of 20% on the distribution and morphology of Si particles is obviously smaller than that of a large deformation of 50%. The electrochemical self-corrosion potential of Sr-modified-Al-7Si alloy is higher than that of unmodified-Al-7Si alloy, and it proves that the distribution and morphology of Si particles have a certain influence on the corrosive properties of Al-7Si alloy. That is, the even fine Si particles are more conducive to improving the corrosive properties of Al-7Si alloy.

Process Parameter Dependent Machine Learning Model for Densification Prediction of Selective Laser Melted Al-50Si Alloy and its Validation

Process Parameter Dependent Machine Learning Model for Densification Prediction of Selective Laser Melted Al-50Si Alloy and its Validation

Guefoams (guest-containing foams) as novel heterogeneous catalysts: Preparation, characterization and proof-of-concept testing for CO2 methanation

The preparation and use of Guefoams as heterogeneous catalyst is reported. The Guefoam catalyst consists of an open-pore Al-Si foam that accommodates a freely mobile guest phase (Ni/CeO2/Al2O3 particles) in its cavities, with neither a physical nor a chemical matrix-guest bond. A eutectic Al-12Si alloy was used as a low-melting matrix precursor to prevent thermal sintering of the active phase during liquid metal infiltration. CO2 methanation was chosen as the reaction test. The activity and CH4 selectivity (close to 100%) achieved with the Guefoam catalyst were similar to those obtained with a packed bed of the same active phase particles, but with the advantages of a structured reactor such as robustness and ease of handling. The thermal conductivity of the Guefoam catalyst is significantly improved with regard to the packed bed of active phase particles, which reduces the temperature gradients in the catalytic reactor, as demonstrated by computational fluid dynamic modelling. Since the permeability of the Guefoam catalyst is 2.7 times that of the packed bed, the pressure drop caused by the passage of a fluid through the novel material is reduced, resulting in a significantly higher catalytic performance index than the packed bed.

Influence of Multi-directional Room-Temperature Forging Process on Microstructure and Mechanical Behaviour of Eutectic Al-12Si Alloy

Influence of Multi-directional Room-Temperature Forging Process on Microstructure and Mechanical Behaviour of Eutectic Al-12Si Alloy

An Al-12Si/ZnS powder inoculant for eutectic silicon in Al-12Si alloy

To obtain high-performance Al-Si-based cast alloys, refinement and modification of Si phases are required. An Al-12Si/ZnS powder inoculant was designed and fabricated using a chemical bath deposition method. The efficiency of the inoculant for modifying the eutectic Si phase in as-cast Al-12Si alloy was studied. Results show that Al-12Si/ZnS powder can significantly refine the eutectic Si in Al-Si cast alloys. The best refinement effect for eutectic Si is achieved with 17.5wt.% Al-12Si/ZnS powder. Coarse long needle-shaped eutectic Si with a length of 18 µm was modified into approximately spherical shape with a diameter of 6.53 µm, which is evenly distributed throughout the alloy. The E2EM model calculation indicates that the inter-plane misfit (Fp) and inter-atomic spacing misfit (Fr) between ZnS and Si are all less than 0.5%, which confirms that ZnS is a potential nucleation site for Si phase. The hardness, tensile strength, and elongation of Al-12Si alloys modified with 17.5% Al-12Si/ZnS powder increase 6.30%, 16.18% and 55.45%, respectively, compared to the unmodified Al-12Si alloy. The fracture behavior of the alloy with 17.5wt.% Al-12Si/ZnS powder is dominated by transgranular fracture supplemented by intergranular fracture.

Efficient fabrication of semisolid nondendritic Al alloy slurry with high quality

Subjecting a normal mechanical vibration to a cooling slope plate, is a proposed method for preparing semisolid nondendritic slurry, named shear-vibration coupling sub-rapid solidification (SCS). Taking Al-8Si alloy as model material, the temperature field and distribution field of solid or liquid phase during SCS were simulated using COMSOL Multiphysics software to primarily choose the optimal processing parameters. Subsequently, the slurries were prepared with the parameters selected according to the simulation results and the microstructures of the slurries were experimentally investigated. Results indicate that the simulation results could provide a basis for roughly choosing the processing parameters, although the calculated solid fractions are always higher than the experimental ones. The processing parameters affect the primary grain size, shape factor and solid fraction mainly through altering the contact duration of melt on the plate, and thus affecting the cooling effect on the melt, nucleation rate, and grain dissociation and proliferation. Experiments with optimized processing parameters show that the primary grains in the slurry have an average size of about 32 µm and shape factor of 1.38, and are quite uniform, even at the highest pouring rate of 2.81 kg·s-1, the size and shape factor are about 46 µm and 1.7, respectively, which implies that the proposed SCS is a promising technology for efficient fabrication of high-quality Al slurry available for engineering applications.

Primary Si refinement and eutectic Si modification in Al-20Si via P-Ce addition

Enhancing the mechanical properties of hypereutectic Al-Si alloys by refining the primary and eutectic Si morphology is very challenging. In this study, the refinement mechanism of primary and eutectic Si morphologies via the simultaneous addition of P-Ce into the Al-20Si alloy was studied. Microstructural analysis revealed that the primary and eutectic Si morphologies were significantly refined, which increased the tensile strength. Furthermore, the addition of Ce, up to 0.6 wt%, can result in the formation of Ce-rich intermetallic phases, which may lead to a significantly increased tensile strength while retaining the ductility of the alloy. The ultimate tensile strength of the Al-20Si alloy increased from 96 to 175 MPa, and the elongation increased from 1.0% to 1.7% with the addition of P-Ce. Moreover, the wear resistance of the alloy improved. The added P and Ce did not react with each other to form an intermetallic compound; therefore, this method can simultaneously refine primary and eutectic Si.

The effect of melt flow induced by RMF on the meso- and micro-structure of unidirectionally solidified Al–7wt.% Si alloy Benchmark experiment under magnetic stirring

This work deals with the effect of melt flow on the solidified structure by RMF. The microstructure of the first non-stirred part of the Al-7Si alloy is columnar. After switching on stirring first a transient zone was formed with eutectic “cupola”. After the first transient zone, the “Christmas Tree Like” microstructure was formed. During the solidification of stirred part, a “tulip-like” interface evolves. During the last two decades, many algorithms were developed to simulate the solidification process for different casting methods like ingots, continuous casting of steel and the direct chill cast of aluminum. Experiments performed under exactly known conditions and with the detailed knowledge of meso- and micro-structures are required for validating these simulations. The aim of this paper is to give a data set to validate these simulations. Unidirectional solidification experiments were performed by using a rotating magnetic field (RMF) to study the effect of melt flow on the solidified micro- and meso-structure of the Al–7wt.% Si binary alloy. The first and the third 1/3 parts of samples were solidified without magnetic stirring, and the second (middle) 1/3 part was solidified by using magnetic stirring. The magnetic induction was 10 mT, the temperature gradient was ∼7 K/mm, and the sample movement velocity was 0.1 mm/s. On the longitudinal section of the sample, the columnar/equiaxed transition (CET), the equiaxed/columnar transition (ECT), the secondary dendrite arm spacing (SDAS), and the macrosegregation (concentration distribution and the amount of eutectic) were investigated. The primary dendrite arm spacing (PDAS) and the grain structure were studied on the cross-section after color etching. The effect of melt flow induced by RMF on the meso- and microstructure of unidirectionally solidified Al–7wt.% Si alloy Benchmark experiment under magnetic stirring .

Influence of Alloying Element Mg on Na and Sr Modifying Al-7Si Hypoeutectic Alloy.

The influence of alloying element Mg on Na and Sr modifying Al-7Si hypoeutectic alloys was investigated. The residual content of Na and the morphology of modified eutectic silicon were characterized. It was found that the alloying element Mg had an enhanced effect on the uptake of sodium in the Al-7Si hypoeutectic alloy modified by the Na-contained modifier. Moreover, the morphology of eutectic silicon of the modified Al-7Si alloys was significantly different from that of Al-7Si-0.4Mg alloys in the present research. When the addition of the modifier is enough, both modifiers could entirely modify the eutectic silicon phase of Al-7Si alloys, while incompletely modified eutectic silicon was observed in both Na-modified and Sr-modified Al-7Si-0.4Mg alloy. It was observed that there was an adhering relationship between the partially modified eutectic silicon with Mg-rich phases. According to the results, it can be proposed that the addition of Mg will affect the solidification behavior of alloys, thereby, leading to the incomplete modification of eutectic silicon phases.