Si Aluminum Alloy Research Articles

Study on the mechanism of improvement of mechanical properties of Al–Mg–Si aluminum alloys by Cu and Ce

First, the stability and tensile properties of the Al/Mg2Si interface doped with alloying elements in the Al–Mg–Si system of aluminum alloys are calculated from first principles. Then, the two experimental alloys with different components were heat treated and the properties were characterized. Calculations show that when the interface is doped with Cu, the tensile stress that the interface can withstand increases to 3.13 GPa; when the interface is doped with Cu and Ce, the tensile strain that the interface can withstand increases to 20% and the tensile stress that the interface can withstand increases to 4.17 GPa; when the interface is doped with Cu and Sc, the tensile strain that the interface can withstand increases to more than 25% and the tensile stress that the interface can withstand increases to 5.08 GPa or more. Characterization of the organization and properties of the experimental alloys showed that Ce not only increased the peak solid solution temperature of the alloys, but also increased the tensile and yield strengths of the alloys in the extruded state by 16% and 13.74%, respectively. During hot extrusion, Ce was able to promote the precipitation of precipitated phases. During aging, the addition of Ce promoted the aging precipitation of the alloy, which not only increased the number of precipitated phases in the alloy, but also refined the precipitated phases and enhanced the aging strengthening effect of the alloy. This study provides technical guidance for the development of new aluminum alloy materials with high strength and low cost.

Study of minor Sc and Zr additions effect on silicon rich Al–Mg–Si aluminum alloy microstructure during Sc multistage thermal treatment

The study addresses the effect of multistage thermal treatment on microstructure formation of Al–Mg–Si series alloy with scandium and zirconium additions in Mg/Si = 0.3 proportion. Basic alloy AlM–Si without Sc and Zr and them modification AlMg1SiZrSc were cast. AlMgSiScZr alloy multi-stage thermal treatment included the following 4 annealing stages –550 °C 8 h + 440 °C 8 h + 500 °C 0.5 h + 180 °C 5 h. For AlMg1Si alloy it was performed following 550 °C 8 h + 180 °C 5 h practice. AlMgSiScZr microstructure was examined using scanning (SEM) and transmission (TEM) microscopy both in as-cast state and after each stage of thermal treatment, for AlMg1Si – both in as-cast state and after final thermal treatment. Coarse intermetallic particles were examined using SEM, while fine particles were examined using TEM. Besides, microhardness values were measured after various thermal treatment stages. It was found out, that coarse intermetallic compounds of Fe2Mg7Si10Al18 type are formed in both alloys during as-cast structure cooling down with such compounds partial dissolution during further thermal treatment. At the same time particles, that can be attributed either to (AlSi)3ScZr or to AlSc2Si2τ-phase, occur in inter-grain boundary of alloys with scandium-zirconium additions. No traces of scandium solid solution discontinuous decomposition have been identified during ingot cooling down. Thermal treatment during 8 h at 550 °C 8 and 8 h at 440 °C results in formation of the phase, which can represent both AlSc2Si2 and Al5SiZr2. At the same time nanoparticles (AlSi)3ScZr do not form during this thermal treatment stage. Heating to 500 °C during 30 min interval allows complete dissolution of magnesium in supersaturated aluminum solid solution. During the final stage β’’ particles (Mg5Si6), representing the major type, form in both alloys; in these conditions scandium does not produce significant effect on their formation.

A model for the precipitate transformation of Mg–Si-rich clusters into Mg5Si6 β″ in Al–Mg–Si aluminum alloys

Abstract A model is developed that describes the kinetics of precipitate transformations in the course of natural and artificial aging of Al alloys containing Mg and Si additions. In our approach, the disordered Mg–Si-rich clusters, which form during natural aging in the highly supersaturated Al matrix, can directly transform into the monoclinic Mg5Si6 (β″), without prior dissolution of the clusters and independent nucleation of β″ in the Al matrix. The transformation rate is evaluated with classical nucleation theory (CNT), assuming that the clusters represent an infinitely large matrix phase in which the β″ precipitates can nucleate. The adapted CNT model is described, and the basic features of the precipitate transformation are discussed in a parameter study. The model can also account for the observation that, during natural aging, the parent clusters occur in a variety of Mg to Si ratios, all of which have a characteristic probability of either transforming into the β″ phase or dissolving.

Effect of welding current and speed on solidification cracking susceptibility in gas tungsten arc fillet welding of dissimilar aluminum alloys: Coupling a weld simulation and a cracking criterion

In order to study the effect of welding current and speed on the solidification cracking susceptibility of weld, gas tungsten arc welding of a fillet weld with a cold filler wire was simulated. Simulation was conducted for dissimilar welding of Al–Cu–Mg to Al–Mg–Si aluminum alloys with an Al–Mg filler metal at the welding current range of 145–175 A and welding speed of 18–24 cm/min. The outcomes of simulations, namely temperature gradient, velocity of isotherms, and weld chemical composition obtained for various welding currents and speeds, were used as inputs for a solidification cracking model. The results showed that the dimensions of the weld profile obtained from the simulation exhibited good agreement with experimental results. However, a discrepancy of 10–23% was observed between experimental and simulated results in relation to one dimension of the weld profile, i.e. the distance between the fillet weld corners. This discrepancy was addressed to identify the underlying reasons. According to the model proposed in this study for solidification cracking of aluminum alloys, both higher welding current and higher welding speed led to a higher susceptibility to solidification cracking. This result was justified by considering factors such as secondary arm spacing of dendrites, isotherm velocity, backfill time, and chemical composition and viscosity of the weld pool. Weldability tests were employed to validate the model's performance for predicting the solidification cracking susceptibility. Thus, the optimal welding parameters can be chosen in accordance with these results and production demands.

Enhancing the strength and structure of Al–Si alloys for biomedical applications through the addition of Sr and Zr grain refiners on secondary AlSi7Mg aluminum alloys

The biomedical industry needs Aluminium alloys with superior corrosion resistance properties for limited applications. The use of Al–Si alloys is often seen as non-bio-compatible alloys due to their lower corrosion resistance properties. The present study aims to enhance the properties of such Al–Si alloys through modification of the Si phases with Strontium (Sr) and Zirconium (Zr) through grain size modification. The present study included the preparation of an Al–Si aluminium alloy utilizing a mixture of different scraps. To refine the grain structure, variable concentrations of Sr and Zr grain refiners were added to the alloy using a stir-casting process. The qualities, including porosity, density, tensile strength, yield strength, and hardness, were assessed according to ASTM standards. The grain size and distribution of intermetallic compounds were investigated by performing a microstructural examination using scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques, to determine the impact of Sr and Zr. The results demonstrate that the inclusion of Sr and Zr grain refiners effectively enhances the grain structure, leading to enhanced microstructural and mechanical properties of the secondary aluminium alloys. This study contributes valuable insights into optimizing the grain refining process for secondary aluminum alloys, offering potential advancements in their industrial applications, particularly in the biomedical industry, where the demand for high-performance biocompatible aluminum materials is steadily increasing.

A high-accuracy dynamic constitutive relation of die-cast Alâ¿¿Si aluminium alloy

Die-cast Al–Si aluminium alloys are increasingly used in the lightweight design of automobiles; their mechanical properties under dynamic loading are crucial and thus must be investigated. The original Johnson–Cook (J–C) constitutive model does not accurately predict the mechanical properties of this alloy, which further affects the reliability of subsequent analysis and calculations. To improve the predictive accuracy of the constitutive model and investigate the dynamic mechanical properties of this alloy, high-speed tensile tests of die-casting aluminium alloy Al–10Si–yCu–xMn–zFe are conducted. The tests are executed at room temperature using a universal electrical testing machine and a high-velocity testing system in a wide strain rate range of 1–800 s−1. The tensile deformation behaviour of this alloy at various strain rates is investigated. The experiments show that the flow stress of the alloy gradually increases with strain and varies significantly with the strain rate. The J–C model is unsuitable for predicting the flow stress of this alloy owing to its unsatisfactory goodness-of-fit. To accurately predict the flow stress of die-cast Al–Si aluminium alloys, we propose a new model based on experiments. Unlike other models, the proposed model incorporates the critical strain and flow stress limit value, which allows the flow stress to be predicted more precisely at various strain rates over a wide strain range of 0–0.17. The experimental data of other die-cast Al–Si alloys validate our model. The goodness-of-fit of the proposed model for this alloy is higher than that of the J–C model, which demonstrates that our model outperforms existing models in terms of estimation accuracy.

A study of microstructure and mechanical properties of friction stir welded joint of Al-Ce-Si-Mg aluminium alloy plates and optimization cum prediction techniques using Taguchi and ANN

In the current research work, the effect of friction stir welding (FSW) on joint strength and evolution of microstructure at the weld zone of the friction stir welded of Al-Ce-Si-Mg aluminium alloy (Al10Mg8Ce3.5Si and Al5Mg8Ce3.5Si) is studied. The experimentations demonstrated that the speed of tool revolution, contour of tool pin and tool movement rate have influence on the quality of the FSW joint of the alloy. It was noticed that the size of grains at nugget zone (NZ) depends upon the speed of tool spin, speed, of tool feed, tool pin contour and composition of the aluminium alloy. The grain size at the bottom of the NZ was discovered to be reducing when compared to that at the top of the NZ. It was also noted that highest hardness was reached at NZ. Lowest hardness was found at heat affected zone (HAZ) and most of the tensile specimens fractured at HAZ. The Taguchi orthogonal array-based design has demonstrated that the tool pin contour had the greatest influence in enhancing the joint strength, followed by speed of tool feed, material composition and speed of tool spin. A speed of revolution of tool of 1000 rpm, tool movement rate of 20 mm/min, triangular contour pin (TCP) tool and Al10Mg8Ce3.5Si aluminium alloy were concluded as the optimum variables of the process. The percentage contribution of each one of these input process parameters on optimum output quality characteristics was also found out and noticed to be lying well within the confidence interval of 95% suggested by the Taguchi design. The current study has shown that the prediction results with artificial neural network (ANN) are better compared to those predicted using statistical methods like Taguchi Techniques.

Study into torsion compression of hybrid blank made of Al—3Ca—Mn—Zn—Fe—Si alloy

Experimental studies of two blanks made of the same Al—3Ca—Mn—Zn—Fe—Si aluminum alloy are performed. The technology for obtaining a composite (hybrid) blank is associated with a torsion compression scheme and consists in the joint deformation of components from materials assembled into a composite blank, as a result of which they seize under the action of pressure, temperature, and also an increasing deformation in the frictional area of the rotating tool. In this case, the temperature in the joint zone does not reach the values typical for the stir welding process. The results of full-scale experiments and computer simulation modeling performed using the found rheological model of the Al—3Ca—Mn—Zn—Fe—Si alloy are presented. Examples of manufacturing of hybrid blank made of various alloys are given for a comparative comparison of the joint quality.

Process parameter optimization for ultimate tensile strength of friction stir welded joint of Al-10Mg-8Ce-3.5Si aluminium alloy plates using Taguchi technique

The Friction stir welding (FSW) process has become a popular method of joining metals, due to its clean and efficient nature of producing welds. The input process parameters: the tool rotation speed, tool feed and tool pin shape are the deciding parameters for an optimum output quality characteristic, the Ultimate tensile stress (UTS) of the weld joint. Here in this research, the Taguchi full factorial design technique is discussed for maximizing the UTS of the weld joint formed in Al-10Mg-8Ce-3.5Si aluminium alloy plates. The ANOVA of means and Signal to Noise ratios for UTS was used to assess the influence of each of the input process parameters on output UTS. The main effect plots of the ANOVA results demonstrated that, the tool rotation speed at level 2 or 1000 rpm, the tool feed at level 3 or 20 mm/min and tool pin shape at level 1 or triangular cross section, gave the optimum results for output UTS. The ANOVA for UTS also showed the percentage contribution of input process parameters; the shape of tool pin as 60.06%, the tool feed as 15.42% and shape of tool pin as 2.41%. The UTS value predicted by the Taguchi analysis was at 108.47 MPa which was in good agreement with the experimentally obtained value of 106.84 MPa. A nonlinear regression equation was developed by correlating the input process parameters, which could be used to predict the optimum UTS results.

The Improved Mechanical Anisotropy of a Commercial Al–Cu–Mg–Mn–Si (2017) Aluminum Alloy by Cross rolling

The optimized thermomechanical process is an effective way to improve and control the properties of metallic alloys. Herein, the influence of unidirectional cold rolling and cross cold rolling on the texture and mechanical properties of a commercial AlCuMgMnSi (2017) alloy is investigated. The Al sheets successfully prepared by the three cold rolling methods have different dominant texture components, and show different texture transformation routes during solution and aging treatments. In addition, the influence of the rolling direction on the texture of the 2017 alloy is discussed. The cross‐rolled sheets subjected to artificial aging show the strongest yield strength of ≈366 MPa and ultimate tensile strength of ≈426 MPa, as well as excellent mechanical anisotropy. Its in‐plane anisotropy (IPA), , and Δr values are 0.7%, 0.576, and 0.042, respectively. The effects of texture and precipitates on the anisotropy of aged 2017 alloys are also discussed separately. This work may help to understand the relationship between rolling direction and the mechanical anisotropy of aluminum alloys and provide a basis for industrial production.

Synergistic inhibition of cerium and alkyl phosphate composite adlayer on pitting corrosion of Al–Mg–Si aluminium alloy

ABSTRACT The nucleation, propagation, and rehabilitation of pitting corrosion of Al–Mg–Si Aluminium alloy (AA6063) are studied in 3%NaCl solution by using electrochemical noise measurement. It shows that the composite film composed of sequent precipitation of ceria and 1-tetradecylphosphonic acid (DPA) presents the best pitting corrosion resistance compared with the independent ceria conversion film or self-assembling DPA film. XPS and microscopic Raman spectra confirmed that Ceria film is an excellent interlayer for the self-assembling of alkyl phosphate on the intermetallic particles in Al alloy. The anti-corrosion performance of Cerium oxides and DPA composite film is totally dependent on the deposition sequence. Prior deposition of ceria and then DPA film can increase the hydrophilicity of Al matrix and AlFeSi intermetallic particles, further promoting the self-assembling of upper DPA molecules, thus dramatically improving the overall and pitting corrosion resistance of AA6063. This could be attributed to the synergistic effects between the upper DPA film and underlying Ce conversion film. On the contrary, Prior assembly of DPA and then deposition of ceria, may significantly degrade their inhibition efficiency.

Friction Stir Welding of the Butt Joints of Al–Mg–Si Aluminum Alloys

Friction Stir Welding of the Butt Joints of Al–Mg–Si Aluminum Alloys

Improving the Tensile Shear Load of Al–Mg–Si Alloy FSLW Joint by BPNN–GA

In order to obtain the joint with a high tensile shear load, the small penetration of tool pin into the lower sheet was applied during friction stir lap welding. The tensile shear loads of the Al–Mg–Si aluminum alloy joint under different process parameter combinations were optimized by combining back propagation neural network and genetic algorithm. The result showed that the hook bent down and the height of cold lap was small. Under the external tension load, the crack propagated along the lap interface or extended downward after reaching the highest point along the cold lap. With the increase of heat input, the tensile fracture mode of joint was more easily obtained. The highest tensile shear load of the joint reached 12.45kN, which was increased by 6.9% than the maximum value before optimization.

Microstructure and Dry Sliding Wear Behaviors of Microwave-Sintered Al-4.4Cu-0.7 Mg-0.6Si-B4C/nGr Hybrid Composites

In recent years, more advanced mechanical and tribological properties have been needed in aluminum matrix composites due to the increasing variety of applications. For this purpose, second-generation aluminum matrix hybrid composites that have two or more different particle reinforcements are being developed today. In this study, in order to improve tribological and microstructural properties, nano-sized graphite and B4C-reinforced Al-4.4Cu-0.7 Mg-0.6Si aluminum alloy hybrid composites were produced. As a sintering method, the microwave sintering technique, which is one of the fast sintering methods, was preferred to prevent and/or minimize the formation of unwanted reaction products. In Al-4.4Cu-0.7 Mg-0.6Si-B4C/nGr hybrid composites, 4 different (3, 6, 9 and 12 wt %) B4C and 1 wt % nGr reinforcements were used. Raw samples, compressed by the one-way cold pressing method under 600 MPa pressure, were sintered in the microwave oven at 550 °C temperature for 60 min. In XRD analyses, whereas any unwanted reaction product (Al4C3, Al3BC, etc.) was not detected, θ-Al2Cu precipitate formations were detected. In hybrid composites where no graphite agglomeration was observed within the matrix, the highest hardness value (103.9 Hv0.05) was determined in the sample containing 6 wt % B4C and the lowest specific wear rate (0.271 × 10–3 mm3/Nm) was determined in the sample containing 12 wt % B4C.

Effect of Friction Time on the Mechanical and Microstructural Properties of AA6061 Joints by Continuous Drive Friction Welding

Friction welding is becoming a viable replacement of conventional joining methods. Continuous Drive Friction Welding (CDFW) is a type of friction welding used to join rods, tubes and similar shapes. Usually, the process contains a friction stage and a forging stage and the process parameters would be ticked accordingly. AA6061 is an Mg and Si aluminum alloy that is widely used in many industries. This research investigates the effect of friction time on the mechanical properties of AA6061 joints made with CDFW and the relation to the microstructure of the material and thermal profiles. It was found that AA6061 does not require a forging stage where solid joints are obtained without forging and did not fracture within the welding zones. Also, it was concluded that the process parameters are to be tailored in a way that produces a specific type of grain structure within the welding areas.

Enhancement of Fluidity and Mechanical Properties of Al – Si cast Alloy

The aim of the study is to investigate the fluidity and mechanical properties of the Al-Si alloy by varying the copper content at three different temperatures with the effect of grain refinement. In this present examination a humble endeavour has been made to know the properties with an ease strategy for sand casting system. Al- Si aluminium alloy is chosen as the base material and copper powder; grain refinement and scrap were added as the compositions. The investigation has been furnished by variying the weight percentage of copper (0-4%), scrap (20-40%) and grain refinement (0-0.4%). Test examples were exposed to various testing conditions and properties have been upgraded. The tensile strength of the material increases with increase of percentage of copper content and the fluidity is balanced by addition of grain refinement. The comparison between microstructure images at 0% copper and 4% copper shows the variation of grain sizes.

Modulation of the natural aging effect on subsequent artificial aging in Al–Mg–Si aluminum alloys with alloying content ∼ 1 wt% through temperature tuning

In this paper, the influence of the natural aging (NA) on the subsequent artificial aging (AA) process in Al–Mg–Si aluminum alloys with alloying content ∼1 wt% was studied. Methods including various aging, hardness testing, transmission electron microscope (TEM), atom probe tomography (APT) etc, were employed. The results show that the NA before AA affects the AA precipitation process adversely under lower AA temperatures, e.g. 150 °C, by suppressing the peak aging hardness, while such effect can be modulated to be positive by increasing AA temperature to over 175 °C. Under higher AA temperatures, transformation of clusters into main strengthening precipitates, β″ phase for example, is promoted. The nucleation probability of these phases is enhanced, through lowering the nucleation energy barrier. As a result, the NA clusters facilitate nucleation and growth of the main precipitates during AA. The overall results proved that the NA effect on the subsequent AA process in the Al–Mg–Si aluminum alloys with alloying content about 1% can be modulated by tuning the AA temperature.

Flow softening behavior and microstructure evolution of aluminum alloy 6061 due to dynamic recovery

Hot compression tests for Al–Mg–Si aluminum alloy were performed on Gleeble-1500 at the deformation temperatures of 300 ∼ 500 °C and strain rates of 0.01–10 s−1. It was found that the flow stress curves exhibit continuous flow softening after reaching the peak value. Microstructure observations indicate that dynamic recovery is the dominant restoration mechanism during the deformation. Continuous flow softening is considered to arise mainly due to thermal softening by deformation heating and microstructural softening by dynamic grain boundary migration. The effect of deformation heating on flow stresses was corrected with the measured instantaneous sample temperature. The dynamic grain boundary migration rate was calculated based on the measured grain thickness. A modified Laasraoui-Jonas model was developed through introducing the flow softening item induced by dynamic grain boundary migration. The predicted flow stresses overall agree well with the experimental data.

A study of the crystallographic pitting behavior of Al-0.54Mg-0.66Si aluminum alloy in acidic chloride solutions

Some specific corrosion environments require Al-Mg-Si aluminum alloy extrusions to have superior corrosion resistance. In order to clarify its corrosion mechanism and enhance its corrosion resistance, the corrosion occurrence, propagation path and corrosion morphology of the alloy was characterized by scanning electron microscope (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). It was found that the corrosion of the alloy first occurred at the grain boundary. Then the grain boundary becomes the origin of the crystallographic pitting after being attacked, and Mg in the Mg5Si6 phase inside the grain is preferentially corroded by precipitate free zone (PFZ), so that the corrosion propagates into the interior of the grain. The morphology of crystallographic pitting presents a regular step-like planes and is always propagated parallel to the direction of {100}Al in the grain. Further, the corroded Mg5Si6 precipitates becomes cathodes in the local area at a later stage, leading to the regular step-like planes has been transformed into dimple-like appearances.

Laser additive manufacturing foam aluminium-12 wt-% silicon with different addition TiH2 foaming agent

ABSTRACTThe aim of this work is to study the effects of laser additive manufacturing on microstructure and mechanical properties of foam Al–12 wt-%Si aluminium alloy with/without TiH2 foaming agent. The results showed that low porosity closed foam Al–12Si was successfully obtained. The effect of processing parameters on the porosity is discussed. The porosity was changed from initial 20.9% without foaming agent to 32.3 and 45.9% with 5 and 10% addition of foaming agent, respectively. Average micro-hardness values of the obtain foam Al–Si alloy is varied from 100 to 130 HV and the shape of compressive stress–strain curve is as the same as foam aluminium made by powder metallurgy and casting methods.