AlSi10Mg Alloy Research Articles

Effect of Nano-Si3N4 Reinforcement on the Microstructure and Mechanical Properties of Laser-Powder-Bed-Fusioned AlSi10Mg Composites

Laser powder bed fusion (LPBF) technology is of great significance to the rapid manufacturing of high-performance metal parts. To improve the mechanical behavior of an LPBFed AlSi10Mg alloy, the influence of nano-Si3N4 reinforcement on densification behavior, microstructure, and tensile property of AlSi10Mg was studied. The experimental results show that 97% relative density of the 3 vol.% nano-Si3N4/AlSi10Mg composite was achieved via optimization of the LPBF process. With the increase in the nano-Si3N4 content, the tensile strength and the yield strength of the composite steadily increase as per the Orowan strengthening mechanism while the elongation decreases. In addition, nano-Si3N4 reinforcement reduces the width of the coarse cell structure region and the thermal influence region of the AlSi10Mg matrix. After annealing, the tensile strength of the nano-Si3N4/AlSi10Mg composite decreases and the elongation increases significantly.

The potency of defects on fatigue of additively manufactured metals

Given their preponderance and propensity to initiate fatigue cracks, understanding the effect of processing defects on fatigue life is a significant step towards the wider application of additively manufactured (AM) parts. Here a novel machine learning (ML) based approach has been developed to predict the fatigue life of laser powder bed fused AlSi10Mg alloy. The four most important parameters, treferred to here as the Wu-Withers parameters, were found to be the applied stress and the projected area, location and morphology of the critical defects. It was found that an Extreme Gradient Boosting model was able to predict the fatigue lives with high accuracy with the importance of these characteristics in limiting fatigue life ranked in the order given above. The model was able to predict the very different lives of samples tested parallel and perpendicular to the build direction in terms of these four W-W parameters indicating that microstructure was of minor importance. In particular the large projected area of the defects on the crack plane when testing parallel to the build direction was found to be primarily responsible for the shorter lives observed for this testing orientation. The fatigue lives were adequately predicted by the more general two variable (stress and projected area) Murakami model, and even more closely predicted by an empirical model (using essentially the same four W-W parameters) for which the ML model corroborated the empirical dependences.

Build quality evaluation of a series of lattice structures of AlSi10Mg using X-ray tomography

Additive manufacturing is a manufacturing technology that has grown from prototyping applications to the production of end-use parts in various industries. It is today possible to produce complex-shaped parts such as cellular or lattice structures in various popular metal alloys relevant to engineering applications. These intentionally designed porous metamaterials allow unique properties that have applications in next-generation aerospace components and medical implants, amongst others. The wide adoption of lattice structures has been in part held back by quality concerns in the manufactured material, including porosity, surface roughness, microcracks, residual stress and microstructural nuances. These issues are generic to all AM materials, but at the scale of lattice structures they have a stronger influence on mechanical and other performance; and are more critical to the successful manufacturing and final application. While lattices have widely studied in the last few years, few comparisons of build quality exist for different designs or architectures. In this work, using the laser powder bed fusion process with AlSi10Mg alloy, we report an extensive and detailed characterization of the build quality of a range of different cellular architectures, utilizing X-ray computed tomography (CT). Some key conclusions are made that can be used to inform future designs, enhancing build success and design confidence. Some recommendations are made regarding the use of CT for lattice structure characterization.

On the Anisotropic Impact Behavior of an Additively Manufactured AlSi10Mg Alloy in Different Heat Treatment Conditions

The present work deals with the anisotropic high-strain rate behavior of laser-powder bed fusion (L-PBF) produced AlSi10Mg alloy in different heat treatment conditions. Impact specimens were produced with different orientations towards building platform and U-notch positions to assess the anisotropic properties. Besides the as-built material, several heat treatments were considered, including annealing, standard T6, hot isostatic pressing (HIP), HIP plus T6, and a recently proposed T6 at high pressure. The high-strain rate behavior was investigated by conducting Charpy impact tests, while material characterization was performed by scanning electron microscopy and x-ray diffraction. Results show that as-built and annealed alloys display significant anisotropic impact properties, whereas samples heat-treated at high temperatures generally have more consistent behavior. A coupled microstructural and fractographic investigation highlights that mitigation of anisotropy descends from the recovery of microstructural heterogeneity of the Si phase after heat treatment at high temperatures. This does not happen for both grain morphology or crystallographic structure, which are not significantly altered after the heat treatment. The present study aims to fill the gap in the literature regarding the anisotropic high-strain rate behavior of additively manufactured Al alloys and provide useful insights for mitigation of anisotropy by heat treatment.

Effects of remelting on the surface morphology, microstructure and mechanical properties of AlSi10Mg alloy fabricated by selective laser melting

Selective laser melting (SLM) is an additive manufacturing technology that uses laser and metal powder to directly manufacture metal parts. The process has good mechanical properties and dimensional accuracy and can be put into use with a simple post-treatment. However, spheroidisation and warpage can easily occur in the forming process, resulting in poor surface quality and high porosity, which are the main limiting factors for the direct application of the parts formed using this technology. Laser remelting is an effective solution to solve these problems. In this research, the microstructure and mechanical properties of AlSi10Mg fabricated by laser remelting using two different scanning strategies were studied, and it was found that both the laser remelting methods can effectively improve the surface quality, reduce the surface roughness (2.3 μm, 4.0 μm) and porosity (0.08%, 0.2%), refine the grains size and improve the hardness. The thermal conductivity and reflectivity of the metal solidification layer are high, the spreading property of molten pool worsens and the width and depth of the molten pool decrease.

Effects of Build Angle on Additively Manufactured Aluminum Alloy Surface Roughness and Wettability

AbstractLaser powder bed fusion (LPBF) was utilized to create a series of aluminum alloy (i.e., AlSi10Mg) 5 mm-diameter support pillars with a fixed height of 5 mm containing varying filet angles and build orientations (i.e., 0 deg, 10 deg, 20 deg, 30 deg, 40 deg, 50 deg, and 60 deg from the normal surface) to determine surface roughness and water wettability effects. From experiments, anisotropic wetting was observed due in part to the surface heterogeneity created by the LPBF process. The powder-sourced AlSi10Mg alloy, typically hydrophobic, exhibited primarily hydrophilic behavior for build angles of 0 deg and 60 deg, a mix of hydrophobic and hydrophilic behavior at build angles of 10 deg and 20 deg, and hydrophobic behavior at 30 deg, 40 deg, and 50 deg build angles. Measured surface roughness, Ra, ranged from 5 to 36 µm and varied based on location. 3D-topography maps were generated, and arithmetic mean heights, Sa, of 15.52–21.71 µm were observed; the anisotropy of roughness altered the wetting behavior, thereby prompting some hydrophilic behavior. Build angles of 30 deg and 40 deg provided for the smoothest surfaces. A significantly rougher surface was found for the 50 deg build angle. This abnormally high roughness is attributed to the melt pool contact angle having maximal capillarity with the surrounding powder bed. In this study, the critical melt pool contact angle was near equal to the build angle, suggesting that a critical build angle exists, which gives rise to pronounced melt pool wetting behavior and increased surface roughness due to enhanced wicking followed by solidification.

Influence of hydrogen vacancy interactions on natural and artificial ageing of an AlMgSi alloy

The influence of hydrogen on the structural evolutions of an Al-Mg-Si alloy during natural and artificial ageing was investigated experimentally. The aim of the study was a better understanding of interactions between hydrogen and crystalline defects and especially vacancies. Experimental data demonstrate that during natural ageing in hydrogen environment, the hardening response is delayed. This is attributed to a slower recovery of excess vacancies linked to a lower mobility. To confirm and quantify the influence of hydrogen on the vacancy migration energy, artificial ageing was carried out in conditions where the vacancy concentration is constant. Hence, long-time annealing treatments were carried out to investigate the influence of hydrogen on the coarsening of rod-shaped precipitates. Using transmission electron microscopy and atom probe tomography, it was demonstrated that the precipitate volume fraction and composition are unchanged under H2 atmosphere but the coarsening kinetic is significantly reduced. This leads to a delayed softening, in good agreement with theoretical estimates. Thus, even a low concentration of hydrogen in solid solution significantly affects the mobility of alloying elements in the aluminium matrix. This is the result of hydrogen-vacancy interactions that lead to an increase of the vacancy migration energy. Based on classical coarsening theories, it was possible to demonstrate that this increase is of about 5% for a concentration of hydrogen close to the vacancy concentration.

Porosity, microstructure and mechanical property of welded joints produced by different laser welding processes in selective laser melting AlSi10Mg alloys

The welding process has been recently introduced to join of the materials fabricated by powder bed fusion (PBF) additive manufacturing (AM) to meet the requirement for the large parts and their repair in service. However, one of the main issues is the high susceptibility to the hydrogen pores occurred during fusion welding of the PBF aluminum (Al) alloys. Autogenous laser welding of a selective laser melting (SLM) AlSi10Mg alloy was firstly carried out in comparison with the casting AlSi10Mg alloy to examine the hydrogen pore characteristics. Single-pass welding with filler powders and laser melting deposition (LMD) welding were then performed on SLM AlSi10Mg alloys to reduce the hydrogen pores. The porosity, microstructure, microhardness and tensile property of the welded joints were investigated. As a result, a high susceptibility to hydrogen pores of SLM AlSi10Mg alloys is occurred in the weld metal (WM) of the welded joint produced by autogenous laser welding and single-pass laser welding due to the high hydrogen content pre-existing in the base metal (BM). However, LMD welding has been shown to effectively reduce the pore size and the porosity generated in the WM of SLM AlSi10Mg alloys. The laser welding of SLM AlSi10Mg alloys produces lower hardness and ultimate tensile strength (UTS) than that of the BM. However, the LMD welding of SLM AlSi10Mg alloys achieves higher hardness and UTS than those of the autogenous laser welding and single-pass laser welding, which is attributed to the refined microstructures and the reduced hydrogen pores in the WM.

Selective laser melting of Al–Si–10Mg alloy: microstructural studies and mechanical properties assessment

Additive Manufacturing (AM) technique is widely recognized by aerospace sectors for its potential to fabricate complex shape components directly from a Computer-Aided Model data (CAM). Selective Laser Melting (SLM) is an innovative method high degree of adaptability among different AM techniques. SLM is one of the AM techniques adopted to produce the three-dimensional complex shape components. Current research work focuses on fabricating an Al–Si–10Mg aluminium alloy by SLM process which is studied for the influence of scanning speed and build orientation on the mechanical strength and surface finish of the as built component compared with as casted specimen. The importance of the sample studied for the scanning speed and built direction is relatively essential exclusively for dynamic applications. The as-built samples surface micrographs was surprisingly refined with a progressively reduced grain size diameter from 7.2 μm to 5.5 μm by increasing scanning speed compared to that of AlSi10Mg parts (∼9.1 μm). The mean layer thickness increased from 20 μm to 30 μm by decreasing the scanning speed from 500 mm/s to 200 mm/s. Attractive advantage of the Orowan mechanism, fine grain strengthening, and the graded interfacial layer, a considerably-high microhardness (135 ± 3.1HV), and enhanced mechanical properties were achieved.

Microstructural evolution and characterization of AlSi10Mg alloy manufactured by selective laser melting

Extensive investigation of the influence of the selective laser melting (SLM) process parameters on the evolution of the molten pool is of great significance to understanding microstructure control and SLM-fabricated part quality. This study focuses on the influence of the scan speed inducing the laser energy changes on the microstructural evolution, texture and phase of AlSi10Mg alloy during SLM. The microstructural evolution and characterization of the SLM-manufactured AlSi10Mg alloy were investigated by scanning electron microscope/electron backscattered diffraction (SEM/EBSD), transmission electron microscope/scanning transmission electron microscope (TEM/STEM) and X-rays diffraction (XRD). The microstructural features of the sample have shown that the primary cellular dendritic structure sizes in the coarse grain zones were about three times larger than those in fine grain zones due to the different cooling rates. Besides, the microstructure boundary contains a eutectic mixture of Al and Si while the matrix is mainly composed of α-Al. The interplanar distance between the fringes are measured as 3.84 Å and 2.86 Å corresponding to the (110) plane of Si and (110) plane of Al. On the other hand, the hardness measurement data show that the sample due to the high scan speed is larger than that of the low scan speed. Meanwhile, the (001) Al texture strength of samples in the low scan speed is stronger than those in the high scan speed. Finally, the XRD analysis reveals that no significant differences are found in the intensity of (111) α-Al, while the intensity of the (200) α-Al presents a difference because of the grain orientation and size.

Lightweight design with metallic additively manufactured cellular structures

Abstract Lightweight design is essential in modern product development and is prevalent in automotive, aerospace, and biomedical applications. The utilization of cellular structure, aided by advancements in additive manufacturing, is among the most effective methods for achieving lightweight design without sacrificing structural integrity and functionality. In this paper, a stress-based structural optimization method is proposed for the design of lightweight components filled with octet functionally graded cellular structures fabricated using selective laser melting (SLM) with the AlSi10Mg alloy. The proposed method includes two main parts: the homogenization-based characterization of SLM-octet-cellular structures and the utilization of the characterized cellular structures for lightweight structure optimum design. Tensile and compression experiments were utilized to validate the proposed homogenization-based characterization method, showing that the simulation and experimental results were in agreement. In addition, the effectiveness of the proposed design optimization method was validated using the three-point bending beam design problem. The experimental results revealed that components filled with functionally graded cellular structures can withstand 15.25$\%$ more load than those with uniform cellular structures. This investigation presents a complete, validated, and industry-oriented lightweight design method, which is useful for the development of future green products.

Optimization of Heat Treatment Parameters of AlSi7Mg Alloy.

Constantly growing requirements concerning the quality of poured machinery components give rise to the need to find new solutions to improve their mechanical and technological properties, considering economic and ecological aspects resulting from energy consumption of the casting and heat treatment processes. This study presents the investigation of the effect of heat treatment on mechanical properties (tensile strength Rm, elongation A5, hardness HBW) of the AlSi7Mg alloy without modification and modified with strontium. Obtained results allowed us to determine T6 heat treatment parameters associated with the improvement of mechanical properties of the alloy with simultaneous limitation of duration of solutioning and aging treatments. The maximum increase in Rm was 67%, and 55% in the case of HBW, with a slight decrease in elongation (approx. 10%) in relation to an alloy not subjected to heat treatment in the adopted scope of tests for the total time of heat treatment of 4–6 h. The increase in elongation of up to 250% requires aging at a temperature exceeding 300 °C, which also causes a decrease in durability and hardness by 20%. Modification of the alloy using strontium before heat treatment facilitates the process of fragmentation and balling of silicone precipitates.

In situ alloying of AlSi10Mg-5 wt% Ni through laser powder bed fusion and subsequent heat treatment

In the current study, the effect of in-situ alloying of AlSi10Mg with 5 wt% Ni (pseudoeutectic composition) through the LPBF additive manufacturing technique was investigated. Fabricated samples underwent supplementary annealing treatment at 300 °C for 15 and 120 min, eventually. During the thermal treatment, the fish-scale grains created after printing inside the melt pools after printing vanished gradually. In the as-built sample, molten Ni particles settled as big chunks of Al3Ni in the center and a thin strip of tiny Ni-rich masses in the borders of the melt pools. FIB/SEM and AFM images revealed that after 15 min annealing, silicon cellular dendrites fragment into fine Si particles, and during annealing for 120 min, the aluminum matrix expels out the supersaturated solute silicon atoms. Consequently, Si atoms leave the substrate and diffuse to pre-existing Si particles in cell walls and the triple junctions. Such a collective diffusion of Si atoms leads to the formation of coarse Si particles widespread in the Al matrix. Based on the XRD outputs, annealing for 15 min had not any major effect on Ni-rich phases. however after 120 min, a more brittle intermetallic shell of a Ni-rich phase formed on pre-exist coarse phases. The comparison of the mechanical properties of the Ni-reinforced AlSi10Mg alloy with those reinforced via the addition of other elements/compounds revealed that in a size range close to AlSi10Mg particles, Ni could not be an appropriate candidate for in-situ alloying through the LPBF method. Furthermore, spheroidization of the silicon particles and formation of fragile Ni-rich intermetallic shells having weak interfacial bonding to the Al matrix during the long-term annealing results in a significant reduction in mechanical strength of the specimens.

Defect-induced cracking and fine granular characteristics in very-high-cycle fatigue of laser powder bed fusion AlSi10Mg alloy

The evolution of defects during very-high-cycle fatigue (VHCF) is important for assessing the lifetime of AlSi10Mg alloy produced by laser powder bed fusion. In the study, VHCF experiments were carried out with an ultrasonic fatigue machine at a stress ratio of −1. Detailed characteristics of short cracks in VHCF were investigated by metallographic serial sections using scanning electron microscope and electron backscatter diffraction. Results show that the defects with nominal stress of 49–60 MPa have different degrees of cracking. As a result of the difference in defect shape, nominal stress and microstructure, fatigue cracks exhibit different cracking modes and propagation paths. Grain refinement behavior occurs at short cracks under VHCF, and the heterogeneous distribution of fine grains underneath the crack surfaces is strongly related to the as-printed microstructure and crack propagation path. Statistical analysis suggests that regardless of the crystal orientation, the misorientation between fine grains and matrix grains tends to be 40–50°. The average crack growth rate in VHCF is approximately in the range of 10−12 ∼ 10−10 m/Cycle.

On the Influence of AlSi10Mg Powder Recycling Behavior in the LPBF Process and Consequences for Mechanical Properties

By using additive manufacturing techniques like the laser powder bed fusion (LPBF) process, parts can be manufactured with high material efficiency because unfused powder material can be reconditioned and reused in consecutive manufacturing jobs. Nevertheless, process by-products like spatters may influence the powder quality and hence alter the mechanical properties/performance of parts. In order to investigate these dependencies, a methodology and a standard build job for the recycling behavior of the lightweight aluminum alloy AlSi10Mg was developed and built with ageing powder in 10 consecutive jobs with no refreshing between the cycles. The powder properties and mechanical performance of parts at static load for two build directions (horizontally and vertically to substrate plate) was evaluated. The influence of build height effects on mechanical performance was investigated as well. The findings may indicate that the coarsening of the powder material during recycling could lead to improved mechanical properties for the AlSi10Mg alloy.

A microcompression study on the mechanical properties and fracture behavior of Be–Al and Be–AlSi10Mg alloys fabricated by laser solid forming

The microstructure and micropillar compression responses of thin-walled Be–Al and Be–AlSi10Mg samples, produced by laser solid forming (LSF), were investigated. Both alloys resembled typical 3-D net-shaped structures. The Be–AlSi10Mg alloy exhibited coarser Be grains embedded in the refined Al net-like matrix owing to a broader solidification region. Owing to the multi-hardening by Si and Mg alloying, the yield strength of the system significantly increased from 150 MPa to 220 MPa. In addition, the failure mode changed from plastic fracture of the Al phase in Be–Al to brittle fracture of the Be phase in Be–AlSi10Mg during microcompression. Based on the theoretical calculation of the yield strength and fracture strength, grain size refinement by the non-uniform nucleation process was dominant factor affecting the Al matrix strength increment of Be–AlSi10Mg. Meanwhile, the critical resolved shear stress of Be was smaller than the ultimate strength of the Al phase strengthened by Si and Mg in the Be–AlSi10Mg alloy. Thus, the failure preferentially occurred in the Be phase rather than the Al phase. These results suggest that improving the fracture strength of the Be phase is important for obtaining high-performance Be–Al alloys after the strengthening of the Al phase by alloying additions and artificial aging measurements.

Influence of tool rotational speed on the microstructural characterization and mechanical properties of friction stir welded Al-Si10Mg parts produced by DMLS additive manufacturing process

Present study investigate the joining of precipitation hardened AlSi10Mg alloy, developed using direct metal laser sintering technique of additive manufacturing using friction stir welding. Consequently, three, single-pass, square butt-welded joints were fabricated from 3 mm thick plates of this alloy, using friction stir welding process at different tool rotational speeds (low, medium and high). Each welded joint was fabricated at the same transverse speed of 50 mm/min, H13 tool steel possessing scrolled shoulder and 3° tilt angle. Microstructural observations show a significant grain refinement within the stir zone, which reduced with the increase in tool rotational speed. This variation was accredited to the significant dynamic recrystallization in the weldment, and change in the morphology and size of the Si-particles. The transverse tensile test results show a considerable drop in the joint efficiency of the welds from ≈48% to ≈42% with the increase in tool rotational speed from low to high.

Problematic of heat treatment and its influence on mechanical properties of selectively laser melted AlSi10Mg alloy

Problematic of heat treatment and its influence on mechanical properties of selectively laser melted AlSi10Mg alloy

Enhancement of electrical conductivity and corrosion resistance by gold-nickel coating of additively manufactured AlSi10Mg alloy

Gold-nickel coatings (Au–Ni) were applied by electrodeposition (ED) and electroless deposition (ELD) on additively manufactured (AM) AlSi10Mg alloy to improve the electrical conductivity and electrochemical behavior. Characterization of the Au–Ni coatings was performed by a scanning electron microscope equipped with energy dispersive X-ray spectroscopy (EDS) and x-ray diffraction to study the tiny features. The surface indentation hardness of the coated alloy was evaluated to study the coating strength. The electrochemical behavior of the as-built part and its counterpart, Au–Ni coated surfaces, were evaluated by conducting potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) in a 3.5% NaCl solution.The results revealed that the Au–Ni coatings with layers thickness of ∼2 and 10 μm, respectively, could overcome the surface critical defects, i.e., pores and flaws. The surface hardness of the coated AM alloy has significantly increased six times due to the hard Ni layer. The electrochemical measurements showed a significant decrease in the anodic dissolution rate and increase in pitting corrosion resistance for the Au–Ni coated surfaces compared to the bare AM AlSi10Mg alloy with the as-built and polished surface condition in chloride solution. This was attributed to the stability of the Au–Ni coatings against the anodic overpotential. Moreover, it was observed that the Au–Ni coatings reduce the electrical resistance of the studied AM alloy by 40%. Consequently, the surface electrical conductivity property of the AM AlSi10Mg alloy was enhanced by both Au–Ni coating procedures.

Properties of Semisolid Parts: Comparison with Conventional and Innovative Manufacturing Technologies

In this paper, wear properties of samples manufactured using thixocasting were compared with those of components obtained using low-pressure die-casting and additive manufacturing in order to assess the relationship between material performance and production technologies, both conventional and innovative. The investigated items were made with AlSi7Mg alloy. First, microstructural analysis and hardness measurements were carried out. Subsequently, pin-on-disk wear tests were performed. Wear behavior of the samples was studied considering both coefficient of friction and wear rate, while the damage mechanism was analyzed by observation of the worn paths using scanning electron microscope, correlating the behavior to the specific microstructure. In addition, the effect of selected heat-treated conditions, relevant for real applications, on wear properties was also evaluated.