Aluminum Alloy AlSi10Mg Research Articles

Improvement of Fatigue Strength in Additively Manufactured Aluminum Alloy AlSi10Mg via Submerged Laser Peening

Improvement of Fatigue Strength in Additively Manufactured Aluminum Alloy AlSi10Mg via Submerged Laser Peening

Study of Eddy Current Testing Ability on SLM Aluminium Alloy.

The detection of defects in aluminium alloys using eddy current testing (ECT) can be restricted by higher electrical conductivity. Considering the occurrence of discontinuities during the selective laser melting (SLM) process, checking the ability of the ECT method for the mentioned purpose could bring simple and fast material identification. The research described here is focused on the application of three ECT probes with different frequency ranges (0.3-100 kHz overall) for the identification of artificial defects in SLM aluminium alloy AlSi10Mg. Standard penetration depth for the mentioned frequency range and identification abilities of used probes expressed through lift-off diagrams precede the main part of the research. Experimental specimens were designed in four groups to check the signal sensitivity to variations in the size and depth of cavities. The signal behavior was evaluated according to notch-type and hole-type artificial defects' presence on the surface of the material and spherical cavities in subsurface layers, filled and unfilled by unmolten powder. The maximal penetration depth of the identified defect, the smallest detectable notch-type and hole-type artificial defect, the main characteristics of signal curves based on defect properties and circumstances for distinguishing between the application of measurement regime were stated. These conclusions represent baselines for the creation of ECT methodology for the defectoscopy of evaluated material.

Failure analysis of fatigue crack propagation in specimens of AlSi10Mg aluminum alloy produced by L-PBF: Effect of different heat treatments

Fatigue crack growth behavior of AlSi10Mg aluminum alloy processed by laser powder bed fusion (L-PBF) was studied for three material conditions: as-built, stress relieved and hot isostatic pressed. An improvement in the fatigue crack growth resistance was found for the heat-treated conditions which was attributed to the residual stress relief induced by the heat treatments. The stress ratio did not affect the fatigue crack growth in regime II which was explained by the absence of crack closure. Fatigue crack growth rates were predicted using a model based on the cyclic plasticity of the tested aluminum alloy. The proposed model agreed well with the experimental results.

The Effect of Sulfuric Acid Anodization on the Electrochemical Properties of Aluminum Alloy AlSi10Mg Prepared by Selective Laser Melting

Aluminum alloy, AlSi10Mg, prepared by selective laser melt (SLM) fabrication was anodized in 9.8% sulfuric acid (Type II) at 15 V for a total of 23 min. Experiments were performed to study the potentiostatic anodization process and its effects on the oxide coating morphology, thickness, and electrochemical properties of the alloy. Prior to anodization, the alloy microstructure is composed of aluminum cells encapsulated in a silicon network. Anodizing the abraded and polished AlSi10Mg surface produced a porous oxide layer with a thickness of 5 μm. The oxide coating weight was 698 ± 29 mg/ft2. The oxide coating forms in the aluminum cells that are isolated from one another by the silicon eutectic phase. In electrochemical tests, the anodic and cathodic potentiodynamic polarization currents were suppressed by factors of 15× and 215×, respectively, as compared to the unanodized controls. The data indicate the anodic oxide coating suppresses the cathodic more than the anodic reaction rate. Linear polarization resistance (R p) values increased by 279× after anodization. The corrosion current density values (j corr) decreased by 133× after anodization. Taken together, the electrochemical data indicate the anodic oxide coating (unsealed) increases the corrosion resistance of the SLM alloy by two orders of magnitude.

Milling of additively manufactured AlSi10Mg with microstructural porosity defects, finite element modeling and experimental analysis

Metal additive manufacturing finds its applications in various sectors, especially the automotive and aerospace industries, wherein weight reduction of components is of paramount importance with respect to performance and fuel consumption. However, additively manufactured metallic components usually undergo post-processing steps to make them ready for end use application. One of these steps is finish machining that is employed to overcome the surface irregularities and poor tolerances produced as a result of additive manufacturing (AM). These finish machining processes involve turning, milling, drilling, reaming, or grinding. This paper presents a three-dimensional (3D) finite element (FE) model to simulate the chip formation during the milling of an AM aluminum alloy AlSi10Mg, while taking microstructural porosity defects into consideration. The material was chosen for its significance in the aerospace and automotive industries. The proposed numerical model was developed using ABAQUS™ and is capable of predicting the cutting forces during the milling of AM AlSi10Mg. The Johnson-Cook strength and fracture models were utilized to simulate the deformation mechanics of the workpiece material subjected to high strains, high strain rates, and high temperatures caused by machining. Two algorithms have been proposed and discussed to model the microstructural defects in the AM metal. Machining tests were performed on an AM AlSi10Mg specimen block to validate the proposed finite element model. To further demonstrate the capability of the proposed model in capturing the influence of porosity on cutting forces, a study has been conducted revolving around the impact of different pore sizes. The chips produced during the machining tests were also collected to compare the morphologies between the numerically simulated chips and the ones obtained experimentally, to further strengthen the validity of the proposed model.

Thermal and hydraulic performance of Al alloy-based 3D printed triangular microchannel heatsink governed by rough walls with graphene and alumina nanofluids as working liquid

Microchannel heat sinks (MCHS) are known for providing enhanced cooling performance but their fabrication requires complex and multi-step processes. The recent development of additive manufacturing has enabled the fabrication of state-of-art monolithic structures that had been impossible to build using conventional methods. In this work, a monolithic cross-flow triangular cross-section MCHS was fabricated from aluminum alloy (AlSi10Mg) using the Direct Metal Laser Sintering (DMLS) process. The microchannel wall surface roughness was measured and the cross-section shrinkage of the microchannels was compared with the initial design hydraulic diameter of 500 µm–1000 µm. The MCHS with an initial design hydraulic diameter of 750 µm possessed a relative wall surface roughness, R a of 7.7%. The triangular cross-section hydraulic diameter underwent a shrinkage of 15.2% and 5.3% in terms of the reduction in angle between adjacent side alloys. Experiments were conducted for Reynolds numbers between 50 and 275 with nanofluids containing graphene and Al2O3 nanoparticles in water/water +10% ethylene glycol; these were compared with their respective base fluids. The Poiseuille number indicated that flow was laminar developed with base fluid and laminar developing with nanofluid as coolant. Despite providing the lowest thermal resistance, the graphene nanoparticles in water created the greatest pressure drop leading to a reduced performance coefficient. Al2O3 nanoparticles in water/water +10% ethylene glycol were found to have 7.7% and 20% better performance coefficients than their respective base fluids.

Properties of an AlSi10Mg Aluminum Alloy for the Production of a Body-Shaped Part Using an SLM Additive Manufacturing Technology

Properties of an AlSi10Mg Aluminum Alloy for the Production of a Body-Shaped Part Using an SLM Additive Manufacturing Technology

Effect of spherical crown texturing and ionized sulfur infiltration on the tribological performance of piston-cylinder liner

In this study, the piston-cylinder liner was treated with single glow photoionization sulfurization of a cast aluminum alloy (AlSi10Mg), and the effect of the spherical crown texture on frictional properties of the piston-cylinder liner were investigated before and after the sulfurization treatment. The treated specimens were characterized and evaluated via microscopic morphological analysis, three-dimensional morphological analysis, X-ray diffraction (XRD), thin film diffraction, microhardness testing, and friction wear experiments. Fluent fluid analysis software was used to develop a flow field simulation model for the spherical crown texture. Results of the study showed that the average friction coefficients of the specimens treated with sulfur infiltration were all lower than those of untreated specimens, and the low friction coefficients were closely related to the laminar structure and weak interfacial bonding of the sulfur infiltration layer. The spherical crown structure effectively affected the stree distribution on surface of the specimens uniformly, which improved the bearing capacity and durability of the specimens, and the surface texture helped reduce the contact area and store the debris generated during the wear process, thus improving the friction performance. Mechanical stamping caused material aggregation on the edges of the weave, which increased the hardness of the edges and thus reduces the increase in wear around the weave. The surface microstructure of the specimens was effectively improved after sulfurization treatment, leading to higher wear resistance for the sulfurized specimens. Given the relative lack of research on the composite ionic sulfurization of piston-cylinder liner spherical crown texture at home and abroad, this experiment provides data support for this direction. The results provide beneficial clues for the design and optimization of the piston-cylinder liner spherical crown structure.

Effect of magnetic field assisted thermal diffusion on microstructure and properties of titanium alloy laser cladding coating

Ti–Al composite coating was prepared on the surface of a titanium alloy by the laser cladding technology and coaxial powder feeding under argon protection. The cladding material was AlSi10Mg aluminum alloy powder. The intermediate sample was thermally diffused at high temperature for 6 h and then placed in a certain intensity of the alternating electromagnetic field until completely cooled. The alloy substrate and coating solidified under the action of the alternating electromagnetic field, and the surface coating of a high strength titanium alloy was obtained. The morphology and microstructure of the composite coating were analyzed by SEM, XRD, and energy dispersive spectroscopy (EDS), and the hardness of the coating was measured. The results showed that the high temperature thermal diffusion promoted the interatomic diffusion; repaired some defects, such as cracks and pores; and eliminated the elemental metals that did not participate in the reaction, and the surface hardness of the coating joint reached the maximum. The electromagnetic stirring makes the titanium alloy coating and substrate bond well, the joint is relatively straight, the number of cracks and pores is obviously reduced, and the comprehensive performance of the coating is improved.

Corrosion-Fatigue Performance of 3D-Printed (L-PBF) AlSi10Mg.

Additive manufacturing (AM) allows for optimized part design, reducing weight compared to conventional manufacturing. However, the microstructure, surface state, distribution, and size of internal defects (e.g., porosities) are very closely related to the AM fabrication process and post-treatment operations. All these parameters can have a strong impact on the corrosion and fatigue performance of the final component. Thus, the fatigue-corrosion behavior of the 3D-printed (L-PBF) AlSi10Mg aluminum alloy has been investigated. The influence of load sequence (sequential vs. combined) was explored using Wöhler diagrams. Surface roughness and defects in AM materials were examined, and surface treatment was applied to improve surface quality. The machined specimens showed the highest fatigue properties regardless of load sequence by improving both the roughness and removing the contour layer containing the highest density of defect. The impact of corrosion was more pronounced for as-printed specimens as slightly deeper pits were formed, which lowered the fatigue-corrosion life. As discussed, the corrosion, fatigue and fatigue-corrosion mechanisms were strongly related to the local microstructure and existing defects in the AM sample.

Effect of internal defects on tensile strength in SLM additively-manufactured aluminum alloys by simulation

This research investigates the effect of internal defects on the tensile strength of Selective Laser Melting (SLM) additively-manufactured aluminum alloy (AlSi10Mg) test parts used for civil aircraft light weight design. A Finite Element Analysis (FEA) model containing internal defects was established by combining test data and the stress concentration factor comparison method. The effect of variation in the number, location and shape of defects on the finite element results was analyzed. Its results show that it is reasonable to use spherical defect modeling. The finite element modeling and analysis methods are also applied to the study of the effect of internal defects on tensile strength in additive manufacturing of other metallic materials. According to the FEA results of single defects at different scales, the formula for calculating the weakening degree of tensile strength applicable to the defective area of less than 15% was established. The result of the procedure is reliable and conservative. This research results can guide the selection of process parameters for the additive manufacturing of aluminum alloys. Further, the research results can promote the application of metal additive manufacturing in designing light-weight civil aircraft structures.

Mechanical and Microstructure Characterisation of the Hypoeutectic Cast Aluminium Alloy AlSi10Mg Manufactured by the Twin-Roll Casting Process

Multi-material designs (MMD) are more frequently used in the automotive industry. Hereby, the combination of different materials, metal sheets, or cast components, is mechanically joined, often by forming joining processes. The cast components mostly used are high-strength, age-hardenable aluminium alloys of the Al–Si system. Here, the low ductility of the AlSi alloys constitutes a challenge because their brittle nature causes cracks during the joining process. However, by using suitable solidification conditions, it is possible to achieve a microstructure with improved mechanical and joining properties. For this study, we used the twin-roll casting process (TRC) with water-cooled rollers to manufacture the hypoeutectic AlSi10Mg for the first time. Hereby, high solidification rates are realisable, which introduces a microstructure that is about four times finer than in the sand casting process. In particular, it is shown that a fine microstructure close to the modification with Na or Sr is achieved by the high solidification rate in the TRC process without using these elements. Based on this, the mechanical properties increase, and especially the ductility is enhanced. Subsequent joining investigations validate the positive influence of a high solidification rate since cracks in joints can be avoided. Finally, a microstructure-property-joint suitability correlation is presented.

Case Study of Additively Manufactured Mountain Bike Stem.

This article is focused on a case study of the topology optimisation of a bike stem manufactured by selective laser melting (SLM) additive technology. Topology optimisation was used as a design tool to model a part with less material used for transferring specific loads than the conventional method. For topology optimisation, Siemens NX 12 software was used with loads defined from the ISO 4210-5 standard. Post-processing of the topology-optimised shape was performed in Altair Inspire software. For this case study, the aluminium alloy AlSi10Mg was selected. For qualitative evaluation, the mechanical properties of the chosen alloy were measured on the tensile specimens. The design of the new bike stem was evaluated by Ansys FEA software with static loadings defined by ISO 4210-5. The functionality of the additively manufactured bike stem was confirmed by actual experiments defined by ISO 4210-5. The resulting new design of the bike stem passed both static tests and is 7.9% lighter than that of the reference.

EFFECT OF SHOT BLASTING PARAMETERS ON THE WATER CONTACT ANGLE ON THE SURFACE OF ADDITIVELY MANUFACTURED AlSi10Mg ALUMINUM ALLOY

In this paper, the effect of shot blasting parameters such as time, pressure, and grit size were studied over the water contact angle of additively manufactured aluminum alloy (AlSi10Mg) surfaces. The Taguchi L9 orthogonal array was implied to set the correlations and interactions between the shot blasting parameters and water contact angle as output parameters. The analysis of variance establishes a good agreement with the results, revealing the time as the most significant parameter with a 41.98% contribution, followed by the pressure (41.57%) and grit size (16.43%). Further, the roughness measurements and scanning electron microscopy analysis of the shot-blasted surfaces validate the variations in the water contact angle.

Topology Optimization of the Clutch Lever Manufactured by Additive Manufacturing.

This article aims to review a redesign approach of a student racing car's clutch lever component, which was topologically optimized and manufactured by Additive Manufacturing (AM). Finite Element Method (FEM) analysis was conducted before and after a Topology Optimization (TO) process in order to achieve equivalent stiffness and the desired safety factor for the optimized part. The redesigned clutch lever was manufactured by using AM-Selective Laser Melting (SLM) and printed from powdered aluminum alloy AlSi10Mg. The final evaluation of the study deals with the experimental test and comparison of the redesigned clutch lever with the existing part which was used in the previous racing car. Using TO as a main redesign tool and AM brought significant changes to the optimized part, especially the following: reduced mass of the component (10%), increased stiffness, kept safety factor above the 3.0 value and ensured the more aesthetic design and a good surface quality. Moreover, using TO and AM gave the opportunity to consolidate multi-part assembly into a single component manufactured by one manufacturing process that reduced the production time. The experimental results justified the simulation results and proved that even though the applied load was almost 1.5× higher than the assumed one, the maximum von Mises stress on the component was still below the yield limit of 220 MPa.

Effect of Defect Variability in Aluminum Alloys on Ultrasonic Fatigue Performance across Additive Manufacturing Platforms

Abstract Optimization of process parameters is a critical step toward realization of component builds across multiple additive manufacturing (AM) platforms and broadening the deployment of AM processes. The main focus of the present work is the quantification of defect variability and fatigue performance of builds across multiple laser powder bed fusion (L-PBF) equipment. This study of variability is predicated upon the hypothesis that, given process variables yielding a similar percentage/type of porosity based on process maps for multiple AM platforms, the defect size distribution across them should be similar. Aluminum alloy (AlSi10Mg) specimens of cylindrical geometry built on three different L-PBF machines are characterized using computed tomography. The distributions of defect size are compared using Kolmogorov-Smirnov tests. Ultrasonic fatigue testing is used to quantify fatigue properties of the builds from the different L-PBF machines under fully reversed loading conditions. Finally, fatigue performance is correlated to the defect distribution in builds across the three platforms.

Experimental Study of the Bending Behaviour of the Neovius Porous Structure Made Additively from Aluminium Alloy

Porous materials bring components not only direct advantages in the form of lightening of constructions, saving of production materials, or improvement of physical properties, but also secondary advantages, which are manifested as a result of their daily use, e.g., in aviation and the automotive industry, which is manifested in saving fuel and, thus, environmental protection. The aim of this article is to examine the influence of the volume ratio of a complex porous structure, the so-called Neovius, on bending properties. Samples with five different relative weights of 15, 20, 25, 30, and 50% (±1%) were fabricated from AlSi10Mg aluminum alloy by Direct Laser Metal Sintering (DLMS) technology. A three-point bending test until specimen failure was performed at ambient temperature on a Zwick/Roell 1456 universal testing machine. The dependences of the bending forces on the deflection were recorded. The maximum stresses, energy absorption, and ductility indexes were calculated to compare the bending behavior of beams filled with this type of complex cellular structure. The results showed that Neovius, with a relative weight of 50%, was much more brittle compared to the other samples, while the Neovius structure, with a relative weight of 30%, appeared to be the most suitable structure for bent components among those tested. This study is a contribution not only to the development of the space and aviation industry but also to the expansion of the knowledge base in the field of material sciences. This know-how can also provide a basis for defining boundary conditions in the simulation of behavior and numerical analyses of 3D-printed lightweight components.

Pulsed Current Effect on the Hard Anodizing of an AlSi10Mg Aluminum Alloy Obtained via Additive Manufacturing

The hard anodizing treatments of cast Al-Si alloys are notoriously difficult. Indeed, their microstructural features hinder the growth of a uniform, compact, and defect-free anodic oxide. In this paper, AlSi10Mg samples, produced via Gravity Casting (GC) and Additive Manufacturing, i.e., Laser Powder Bed Fusion (L-PBF), were hard anodized in a sulfuric acid bath, in order to verify how the particular microstructure obtained via L-PBF affects the thickness, hardness, compactness, and defectiveness of the anodic oxide. Moreover, for the first time, Pulsed Direct Current (PDC) procedures were used to perform the hard anodizing treatments on additively manufactured AlSi10Mg alloy. Several combinations of temperature and electrical parameters, i.e., current density, frequency, and Duty Cycle, were tested. The anodized samples were characterized through optical microscopy analysis, Scanning Electron Microscopy (SEM) analysis, and accelerated corrosion tests, i.e., Potentiodynamic Polarization (POL) and Electrochemical Impedance Spectroscopy (EIS) measurements. The PDC procedures allowed improvement of the compromise between evenness, compactness, and defectiveness. Among the attempted PDC procedures, a specific combination of electrical parameters and temperature allowed the best results to be obtained, i.e., the highest hardness and the lowest volumetric expansion values without compromising the oxide quality rating and the corrosion resistance behavior. However, none of the attempted PCD strategies allowed the hardness values obtained on samples produced via GC to be reached.

High-velocity impact fragmentation of additively-manufactured metallic tubes

In this paper, we have developed and demonstrated a novel high-velocity impact experiment to study dynamic fragmentation of additively-manufactured metals. The experiment consists of a light-gas gun that fires a conical nosed cylindrical projectile, that impacts axially on a thin-walled cylindrical tube fabricated by 3D printing. The diameter of the cylindrical part of the projectile is approximately twice greater than the inner diameter of the cylindrical target, which is expanded as the projectile moves forward, and eventually breaks into fragments. The experiments have been performed for impact velocities ranging from ≈180m/s to ≈390m/s, leading to strain rates in the cylindrical target that vary between ≈9000s-1 and ≈23500s−1. The cylindrical samples tested are printed by Selective Laser Melting out of aluminum alloy AlSi10Mg, using two printing qualities, with two different outer diameters, 12 mm and 14 mm, and two different wall thicknesses, 1 mm and 2 mm. A salient feature of this work is that we have characterized by X-ray tomography the porous microstructure of selected specimens before testing. Three-dimensional analysis of the tomograms has shown that the initial void volume fraction of the printed cylinders varies between 1.9% and 6.1%, and the maximum equivalent diameter of the 10 largest pores ranges from 143μm to 216μm, for the two different printing conditions. Two high-speed cameras have been used to film the experiments and thus to obtain time-resolved information on the mechanics of formation and propagation of fractures. Moreover, fragments ejected from the samples have been recovered, sized, weighted and analyzed using X-ray tomography, so that we have obtained indications on the effect of porous microstructure, specimen dimensions and loading velocity on the number and distribution of fragment sizes. To the authors’ knowledge, this is the first paper (i) providing a systematic experimental study (34 impact tests) on the fragmentation behavior of printed specimens, and (ii) including 3D reconstructions of dynamic cracks in porous additively-manufactured materials.

Highly ductile and mechanically strong Al-alloy/boron nitride nanosheet composites manufactured by laser additive manufacturing

Laser metal deposition (LMD) is one of the prospective additive manufacturing (AM) processes to fabricate metal-based nanocomposites. In this study, aluminum alloy (AlSi10Mg) was reinforced by boron nitride nanosheets (BNNSs) via LMD method. High speed ball-milling was used to mix AlSi10Mg powder with BNNSs at fraction range 0.05–0.2 wt%. Comprehensive morphology analysis as well as structure-property relations were investigated. The study showed that adding BNNSs into Al-alloy via LMD process not only promoted the hardness (40 %) and mechanical properties of the matrix (24 %, 100 % and 96 % increments in ultimate tensile strength, yield strength and Young's modulus, respectively), but also significantly improved its ductility (∼300 % increase). This has been observed clearly in fracture analysis where ductile fracture features were the dominant mode for all prepared samples. According to the observations by optical microscopy and electron backscattered diffraction, BNNSs have a crucial effect on grain refinement; grain size reduced from ∼30.4 to 17.5 μm upon the addition of 0.2 wt% of BNNSs. In addition, during LMD process, hard mesophase of aluminum nitride was formed which assisted BNNSs in reinforcing the Al-alloy. The results helped to understand the microstructure changes and mechanical properties improvements when LMD method was used.