Eutectic Si Research Articles

Influence of high-intensity horizontal mould vibration on the density, grain refinement and mechanical characteristics of a die cast aluminium alloy (LM21)

The present investigation analysed the effect of mould vibration using an indigenous vibrating setup on the physical, metallurgical and mechanical properties of die cast A308 alloy. The alloy was vibrated at a constant amplitude of 31µm at 75, 100, 125 and 150 Hz. The work aims to generate more nucleation sites during melt solidification by fragmenting dendrites and Si particles. To examine the changes in metallurgical characteristics, α-Al, secondary dendritic arm spacing, length, width and aspect ratio of eutectic Si particles were studied using optical microscopy, scanning electron microscopy and X-ray diffraction analysis. It was observed that the size of α-Al, secondary dendritic arm spacing, length, width and aspect ratio of eutectic Si particles were decreased by 47%, 53%, 65%, 12% and 61%, respectively. Whereas, the shape factor and density of the alloy were enhanced by 25% and 1.62% compared to stationary cast samples because of mechanical vibration treatment at an optimum frequency of 100 Hz. Mechanical testing findings demonstrated a 13%, 20%, 15% and 20% increase in the parameters such as yield strength, ultimate tensile strength, percentage elongation and microhardness at 100 Hz when compared to the stationary cast sample. Grain refinement, uniformity of structure, improvement in the morphology of metallurgical characteristics, decreased porosities and subsequent increase in density were all factors that contributed to the improvement. Tensile test samples with scanning electron microscopy fractography demonstrated transgranular brittle fracture and a few ductile rips.

Corrosion of Secondary Hpdc A365 (AlSi10MnMg(Fe)) Alloys for Automotive Applications

Al alloys with suitable mechanical properties and castability are widely used for thin-wall structural HPDC components with complex shapes. Al alloy A365 (9-11.5% Si, 0.4-0.8%Mn, 0.1-0.6% Mg, 0.25% Fe max.) is typically produced using primary Al (raw material) to control/minimize the impurity Fe content. Secondary A365, made using recycled end-of-life material, with equivalent mechanical properties as the primary alloy, provides an opportunity to reduce life cycle greenhouse gas (GHG) emissions from light-duty vehicles through improved end-of-life material recovery. The primary alloy is susceptible to micro-galvanic corrosion, where the eutectic a-Al phase serves as the anode and the eutectic Si phase, and incorporated secondary intermetallic phases serves as the cathode. The purpose of this work is to determine the extent to which utilization of end-of-life materials alters the microstructure and, in turn, corrosion (anode and cathode kinetics) of secondary A365, as revealed by electrochemical measurements.

A Study on the Interrelationship between the Microstructural Features and the Elevated Temperature Strength of Multicomponent Al-Si-Cu-Ni Casting Alloys

The elevated temperature strength of multicomponent Al-Si alloys is greatly affected by the volume fraction and the interconnectivity of hard phases formed upon solidification. In the present investigation, such influences were examined for two Al-Si-Cu-Ni alloys with different total volume fractions of hard phases. To control the microstructural features related to the size of the phase, the specimens were prepared with and without ultrasonic melt treatment (UST) at different cooling rates. The microstructures of the alloys were composed of primary Si, eutectic Si, (Al,Si)3(Zr,Ni,Fe), Al9FeNi and Al3(Cu,Ni)2 phases. The microstructural features, such as the size and aspect ratio of each phase, changed with UST and cooling rate, and accordingly, the elevated temperature strength at 350 oC was changed. The alloy with a high volume fraction of about 30 vol.% exhibited increased elevated temperature strength at 350 oC when ultrasonic melt treated, and the alloy having a volume fraction as low as about 18 vol.% exhibited the opposite results. Considering the microstructural features of the multi-component Al-Si alloy, a hexagonal shear-lag model was suggested, based on the well-known shearlag model proposed by Nardone and Prewo (Scr. Metall. 20;1986:43-48). Using the 2-D microstructural factors such as the size, aspect ratio of the phase and secondary dendrite arm spacing, the elevated temperature strength was calculated and compared with the measured value. Based on the hexagonal shear-lag model, the influence of microstructural factors on the elevated temperature strength was discussed for multi-component Al-Si-Cu-Ni alloys.

Microstructures and mechanical properties of A356-SiCp/A356 cladding composite materials prepared by vacuum Solid–Liquid casting

A356-SiCp/A356 cladding composite materials were prepared by vacuum solid–liquid casting. The interfacial bonding, microstructure, and mechanical properties of this cladding composite material were investigated. The microstructures indicated that there was a good metallurgical combination interface between A356 and SiCp/A356 of the cladding composite material. The tensile tests showed that the bonding strength of the interface was lower than that of the two materials, but fracture occurred on the A356 side as the macrointerface perpendicular to load, while the tensile strength of A356 was higher than that of the cladding composite material. This fracture phenomenon could be explained by the remelt mechanism and grain coarsing mechanism. As a result of the topmost layer of the A356 alloy in contact with the SiCp/A356 composite slurry being remelted when the SiCp/A356 composite slurry was poured, an inseparable metallurgical combination interface was formed, and α-Al grains and eutectic Si on the A356 side near the interface were coarser than those on the interface. The results of this research can provide a reference for manufacturing automotive brake discs with cladding composite materials.

Mo–Si–B alloys for ultra-high-temperature space and ground applications: liquid-assisted fabrication under various temperature and time conditions

Boron-doped molybdenum silicides have been already recognized as attractive candidates for space and ground ultra-high-temperature applications far beyond limits of state-of-the-art nickel-based superalloys. In this work, we are exploring a new method for fabricating Mo–Si–B alloys (as coatings or small bulk components) by utilizing a pressure-less reactive melt infiltration approach. The basic assumption of this approach is a synthesis of binary and/or ternary and complex intermetallic phases (silicides, borides, borosilicides), through a direct interaction of Si–B melt with molybdenum. The main purpose of this work was to examine the effect of temperature and time of Si–B melt interaction on the structure and morphology of the formed reaction products. For this purpose, sessile drop experiments were carried out on the eutectic Si–3.2B (wt%) alloy/Mo couples at temperature varying between 1385 and 1550 °C and holding time between 10 and 30 min. The solidified sessile drop couples were subjected to microstructural characterization by means of light microscopy and scanning electron microscopy analyses performed both at “top-view” and cross-sectioned interfaces. The phases formed within the interaction zone were identified by using TEM/SAED and XRD techniques. It was documented that a thickness of both main product layer (MoSi2 + Mo5Si3) and boron-rich interlayer increases with raising temperature and time of the Si–B melt interaction with Mo substrates.

High power laser powder bed fusion of AlSi10Mg alloy: Effect of laser beam mode

High power laser powder bed fusion (HP-LPBF) is a burgeoning additive manufacturing technology for the high-efficiency and high-accuracy build of metallic parts. However, studies about the effect of laser beam mode on build quality is still insufficient. In this paper, both a 2 kW multi-mode fiber laser and a 2 kW Gaussian mode fiber laser are used for the HP-LPBF of AlSi10Mg alloy. Firstly, the relative density (RD) of the HP-LPBF samples has been studied for parameter optimization. The RD of the samples built with the multi-mode laser beam (hereafter called as Multi-mode sample) first increases and then remains stable with the increase of laser energy density Ev. When Ev is no less than 50 J/mm3, the RD of the Multi-mode sample is higher than 99.5%. In contrast, the RD of the samples built with the Gaussian mode laser beam (hereafter called as Gaussian sample) first increases and then decreases with the increase of Ev, and the highest RD is just 95.87 ± 0.2% at the Ev of 50 J/mm3. Based on this, the Multi-mode sample and Gaussian sample built with the same parameters (Ev=50 J/mm3) are chosen as the typical contrast samples for further studies of surface quality, microstructure and tensile property. The results show that the typical Multi-mode sample presents a flatter surface and a lower surface roughness compared with the Gaussian sample. The phase composition of both the two kinds of samples consists of α-Al matrix and eutectic Si. However, the solidification microstructure varies with laser beam mode. The Multi-mode sample presents a columnar solidification microstructure with a strong< 100 > texture along the build direction. In contrast, the solidification microstructure of the Gaussian sample is a mixture of equiaxed grains and short columnar grains. The crystallographic orientations of the two kinds of grains are multifarious, leading to a much weaker texture. The tensile strengths and elongation of the Multi-mode sample are significantly better than those of the Gaussian sample. The effect mechanisms of the laser beam mode on relative density, surface quality, microstructure and tensile property have also been revealed.

Cellular automaton simulation and experimental validation of eutectic transformation during solidification of Al-Si alloys

The morphology of eutectic silicon in solidification microstructure is critical to the performance of Al-Si-based alloys. Simulating eutectic Si phase formation has been a challenge in ICME (integrated computational materials engineering) based design and manufacturing of solidification products of Al-Si-based alloys. In this study, our previous three-dimensional (3-D) cellular automaton (CA) model for α-Al dendritic growth was extended to include eutectic (α-Al + Si) transformation in multi-dendrite domains, providing a complete solidification simulation of critically important Al-Si based alloys. The quantitative results of the Si phase in the eutectic microstructure were experimentally validated using scanning electron microscopy and deep etching techniques. The simulation results show a good agreement with the experimental observations and calculations by the Scheil model and lever rule. This 3-D CA model is useful for predicting and optimizing the solidification microstructure including eutectic transformation during solidification processing such as casting, potentially welding, and additive manufacturing.

Towards strength-ductility synergy through an optimized two-stage solution treatment in Al–7Si–3Cu-0.5Mg alloys

In order to obtain superior mechanical properties, the incipient melting and maximum dissolution of Cu-containing phases, spheroidization and coarsening of eutectic Si phase in Al–Si–Cu–Mg alloy are important factors that should be considered during solution treatment. However, the conventional single-stage solution treatment was difficult to meet this requirement. In this study, an optimized two-stage solution treatment (495 °C/8 h + 515 °C/4 h) was established for Al–7Si–3Cu-0.5 Mg casting alloys through systematically investigating the microstructure evolution at different solution temperatures (470 °C, 495 °C, 515 °C and 525 °C). The first stage (495 °C/8 h) was applied to dissolve most Cu-containing phases and avoid incipient melting, while the employ of the second one (515 °C/4 h) was to promote fast spheroidization of eutectic Si phase and prevent severe overheating. Two modified quality indexes evaluated the synergy of strength and ductility indicated that the optimized two-stage solution treatment and the subsequent aging treatment (175 °C/8 h) gave rise to an optimization (QIU = 537.1 MPa, QIT = 0.47) on the strength and ductility of Al–7Si–3Cu-0.5 Mg alloys, as compared with the alloys (QIU = 527.4 MPa, QIT = 0.46) under the conventional heat treatment including a single-stage solution treatment (515 °C/16 h). The strength-ductility synergy was arisen from the fuller dissolution of Cu-containing phases, the finer eutectic Si phase, the depletion in number density of micropores and the precipitation of nano-sized Q′ and θ′ particles. 0.3 wt% Zr addition further increased the modified quality indexes (QIU = 549.5 MPa, QIT = 0.50), which was attributed to the grain refinement and the formation of nanoscale Al–Si–Zr precipitates. Furthermore, the fracture mechanism of the obtained alloys was also discussed.

Solidification behavior and enhanced properties of semi-solid Al–8Si–0.5Fe alloys fabricated by rheo-diecasting

Compared with the high pressure diecasting, rheo-diecasting has an advantage in decreasing defects, refining microstructure and improving properties. In the present work, an Al–8Si–0.5Fe alloy with a good combination of mechanical property and thermal conductivity was obtained by rheo-diecasting. The solidification behavior, mechanical properties, and thermal conductivity of the alloy under rheo-diecasting were discussed. The results demonstrated that the chilling effect and shearing vibration not only affected the primary solidification on the vibrating contraction sloping plate, but also the secondary solidification in the remaining liquid during rheo-diecasting. The rheo-diecasting alloy possessed spherical primary α1-Al grains and secondary α2-Al grains, small-sized Al5FeSi phases, eutectic Si phases, and low porosities, and thus exhibited the high mechanical properties and thermal conductivity. With decreasing pouring temperature from 690 °C to 670 °C, the size of primary α1-Al grains, secondary α2-Al grains, Al5FeSi phases and eutectic Si phases was decreased due to high cooling rate, which further improved the mechanical properties and thermal conductivity of the alloy.

Effect of ageing and thermal exposure on microstructure and mechanical properties of a HPDC Al–Si–Cu–Mg alloy

Mechanical behavior and microstructure evolution of a newly developed high strength die casting Al–13Si-0.25Cu alloy (in wt%) were investigated under as-cast, peak-aged and thermal-exposed conditions. In the as-cast condition, the alloy has a yield strength (YS) of 213 MPa and an elongation (El) of 4.6%. The alloy YS is further improved to 265 MPa after T5 ageing treatment. The enhancement of YS after ageing is attributed to the precipitation of nanoscale β″, Q′ and θ′ phase from the α-Al matrix. After thermal exposure at 350 °C for 100 h, however, these precipitates mostly dissolve into the α-Al matrix and the ultrafine eutectic Si networks undergo breaking and coarsening, reducing YS to 117 MPa while enhancing the El to 10.3%.

Elucidating thermal conductivity mechanism of Al-9Si based alloys with trace transition elements (Mn, Cr, V)

The effects of trace transition elements (Mn, Cr, V) on the solidification microstructure and the thermal conductivity of Al-9Si based alloys have been investigated. It was found that the effect of Mn, Cr, V on the solidification behavior and solidification microstructure is mainly related to α-Al grains via affecting heterogeneous nucleation and growth restriction, while no significant effect on the solidification behavior and microstructure of eutectic Si was observed. Compared with factors including grain size of α-Al and morphology characteristics (e.g. size, spacing, and shape factor) of eutectic Si, the solid solubility in Al matrix is confirmed to be one of the most important factors affecting thermal conductivity. Due to the larger partition coefficient of V compared with Cr and Mn, the solid solubility and the lattice distortion of α-Al in Al-9Si-xV alloy were increased significantly, thus the thermal conductivity of alloy was decreased steeply from 171.7 to 152.3 W/m·K with the content of V increasing from 15 to 1010 ppm. A linearly fitted curve reflecting the relationship between the content of the transition elements and the thermal conductivity of alloys has been proposed, which can be used to optimize the alloy composition in subsequent remelting or recycling process. Furthermore, two thermal conductivity models (H-S model and Maxwell model) also have been used to evaluate the effect of Mn, Cr, V on thermal conductivity, in which the thermal conductivity of α-Al was corrected based on the measured solid solubility. In this way, the data correlation between the experimental and fitted value based on H-S model and Maxwell model is increased from 0.18 to 0.96. These obtained results could be helpful to precisely control the composition and further improve the thermal conductivity of Al-Si based alloy during the primary production and / or recycling process.

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.

Comparative Study of Microstructure and Properties of Hypoeutectic Al-Si Alloys Being Cast With and Without Melt Thermal Treatment

This study investigated the microstructure and mechanical properties of several hypoeutectic Al-xSi (x = 0, 1, 3, 5, 7, 9) alloys prepared with and without melt thermal treatment. The overall study showed a trend of effective utilization of grain refiner until the transition point (3 wt.% Si) and the slope of graph between grain size vs. wt.% of Si remain similar for the samples prepared with or without chemical refinement. This also indicates that the role of Si in decreasing grain size is more dominating than the poisoning of Ti above transition point. Melt thermal-treated alloys exhibited less significant changes in grain size, especially below the transition point, but significant changes in their mechanical properties. The melt thermal treatment also causes partial refinement of eutectic Si particles by which the coarse silicon particles are broken up into smaller pieces and this has neither been observed in unrefined alloys nor refined alloys.

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 Ultrasonic-Assisted Modification Treatment on the Microstructure and Properties of A356 Alloy.

Ultrasonic treatment was applied to an A356 aluminum melt with different modifiers, and the effects of ultrasonic treatment on the structure and properties of the A356 alloy were studied. The results showed that α-Al was effectively refined with different ultrasonic modification treatments. In particular, ultrasonic treatment showed the most obvious refinement with macroscopic grains of unmodified alloy and optimized the refinement of secondary dendrite arm spacings in the Sr/Ce synergistic alloys. The eutectic Si of the unmodified A356 alloy had no obvious change after the ultrasonic treatment, but the branch diameter of the eutectic Si reduced in the Sr and Sr/Ce modification alloys after the ultrasonic treatment. The ultrasonic treatment significantly improved the ultimate tensile strength and elongation of the as-cast A356 alloy with the unmodified material, which was due to refinement of the α-Al grains by the ultrasonic treatment. After the T6 heat treatment, the ultimate tensile strength values of the alloys showed no obvious change due to the ultrasonic treatment, but the plasticity of the alloy was significantly improved. Mg2Si precipitation was the dominant strengthening mechanism during the T6 heat treatment, while the plasticity was determined by the size and distribution of the eutectic Si. Acoustic cavitation caused by the ultrasound-activated impurities and the induced heterogeneous nucleation and supercooled nucleation in the groove melt was the main cause of the α-Al refinement, the eutectic Si modification and the improvement in the mechanical properties.

Quality of automotive sand casting with different wall thickness from progressive secondary alloy

Abstract This paperwork is focused on the quality of AlSi6Cu4 casting with different wall thicknesses cast into the metal mold. Investigated are structural changes (the morphology, size, and distribution of structural components). The quantitative analysis is used to numerically evaluate the size and area fraction of structural parameters (α-phase, eutectic Si, intermetallic phases) between delivered experimental material and cast with different wall thicknesses. Additionally, the Brinell hardness is performed to obtain the mechanical property benefits of the thin-walled alloys. This research leads to the conclusion, that the AlSi6Cu4 alloy from metal mold has finer structural components, especially in small wall thicknesses, and thus has better mechanical properties (Brinell hardness). These secondary Al-castings have a high potential for use in the automotive industry, due to the thin thicknesses and thus lightweight of the construction.

Influence of the evolution of heat-resistant phases on elevated-temperature strengthening mechanism and deformation behavior in Al–Si multicomponent alloys

Evolution of the heat-resistant phases and deformation behavior of α-Al matrix of four alloys have been characterized by SEM and EBSD. The strengthening mechanisms influenced by morphology and distribution of the heat-resistant phases were described. And the strain contouring of the α-Al matrix after deformation was rendered. The heat-resistant phases with block-like as reticular or semi-reticular network distribution exist in grain boundary can effectively provide elevated-temperature strength for alloys, while the strain contouring of α-Al matrix is mainly concentrated in the area with fewer intermetallic phases. It is shown that intermetallic phase evolution corresponds to extrusion treatment and the formation of eutectic Si and primary Si, highly interconnected networks of intermetallic phases exist in the alloy in which the primary Si and the eutectic Si are simultaneously present or disappeared. And only the disappearance of the primary Si and the extrusion treatment will destroy the network structure of the intermetallic phases. A reticular or semi-reticular microstructure is more capable of matching strength and plasticity and facilitating uniform deformation of the α-Al matrix. And the destruction of this microstructure is allowed to accommodate more plastic strain before failure.

Effects of Ni content on microstructure and wear behavior of Al–13Si–3Cu–1Mg-xNi-0.6Fe-0.6Mn alloys

As one of the lightweight and wear-resistance metallic structural materials, cast Al–Si alloys have been widely studied in automobile and defense industries to meet the greater demands for elevated-temperature wear-resistance properties. In this study, the effect of Ni content on the microstructure and wear behavior of Al–13Si–3Cu–1Mg-xNi-0.6Fe-0.6Mn alloys were investigated by thermodynamic modeling, X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and ball-on-disk reciprocating sliding test. The results show that the θ-Al2Cu and γ-Al7Cu4Ni phases are disappeared, while the δ-Al3CuNi, ε-Al3Ni, and T-Fe phases are formed with the increasing of Ni contents. The 3-D network structure is composed of α-Al matrix, eutectic Si, Q, Ni-rich, and Al15(Mn, Fe)3Si2 phases, which leads to the best hardness and wear-resistance of the alloy with 2 wt% Ni. The fracture and debonding of excessive coarse ε-Al3Ni phase deteriorate the wear-resistance and ductility of the 3Ni alloy. The main wear mechanisms of the tested alloys are abrasive, delamination and oxidative wear at 25 °C and convert to adhesive wear at 350 °C.

Effect of heat treatment on AlSi10Mg lattice structure manufactured by selective laser melting: Microstructure evolution and compression properties

In this paper, the effect of artificial aging (AA), solution heat treatment (SHT) and solution heat treatment + artificial aging (SHA) at different time and temperature on the microstructures and compression properties of AlSi10Mg lattice structures manufactured by selective laser melting (SLM) were systematically investigated. The microstructure of as-built sample consists of elongate cellular α-Al matrix decorated with eutectic Si network boundaries. After AA, the cellular structure is still maintained and there are a lot of nano-sized Si precipitates of the cellular structure. After SHT and SHA, the unique microstructural characteristic of as-built disappear, whereas the Si-rich cellular boundaries are transformed into Si particles and Si particles become coarse. The Si particles inhibit grain growth in the α-Al matrix, the samples have a strong 〈001〉 orientation. The digital image correlation (DIC) method was adopted to analyze the strain field and strain distribution during the compressive process. The results reveal that the SHA has the best compression properties and stable deformation mode. And the fracture mode changed from the initial brittle fracture to ductile fracture. The correlation between the microstructure evolution and the compression properties and the strengthening mechanism were discussed. Finally, the finite element analysis was carried out to simulate the static response of the lattice structure based on the optimal heat treatment parameters. The results can be used as a reference for control of the microstructure characterization and compression properties of AlSi10Mg lattice structure after heat treatment. • The correlation between the microstructure evolution and the strengthening mechanism are discussed. • With the increase of temperature and time, the Si-rich cellular boundaries are transformed into Si particles. • The precipitate of needle-like AlFeSi have a negative effect on the compression properties of AlSi10Mg lattice. • The Si particles inhibit grain growth in the α-Al matrix, the samples have a strong <001> orientation.

Microstructure and mechanical property of high power laser powder bed fusion AlSi10Mg alloy before and after T6 heat treatment

ABSTRACT This paper focuses on the microstructure and mechanical property of the high power laser powder bed fusion AlSi10Mg alloy before and after T6 heat treatment. The results demonstrate that the as-printed sample presents a columnar grain structure along the build direction and a strong <100> texture. Inside the columnar α-Al grains, there are cellular dendrites decorated with network eutectic Si. Both the α-Al matrix and eutectic Si have high-density dislocations. Besides, nano-twins and stacking faults are observed in eutectic Si. After T6 treatment, although the α-Al matrix still exhibits a columnar solidification feature, the cellular dendrites disappear and the proportion of equiaxed grains increase. And the eutectic Si presents as separate plates or nanoscale particles, in which nano-twins and stacking faults are not found. The tensile property anisotropy decreases and the strength-ductility balance improves after T6 treatment. The evolution mechanisms of the microstructure and tensile property are revealed.