Die-cast Aluminum Alloy Research Articles

Numerical Determination of Initiation Fracture Toughness of High-Pressure Die Cast Aluminium Metal Matrix Composite Material Using FEM Analysis

The critical stress intensity factor for high-pressure die casted aluminium metal matrix composite material is rarely reported in the literature. The understanding of this parameter is very much essential for exploring the application of this material in automobile and aviation industries relying on light-weight materials. In the present study, critical stress intensity factor for pressure die cast aluminium alloy (ADC12) has been determined numerically, which compares well with experimental values. The variation due to fracture specimen thickness and relative crack size is also studied for the material.

Corrosion Behavior of Diecast Mg–Al–Mn–Ca–Si Magnesium Alloy

The corrosion behavior of diecast Mg–Al–Mn–Ca–Si (AMXS6020) magnesium alloy with superior flame-retardance and heat-resistance was systematically investigated and compared to diecast AZ91D magnesium alloy and ADC12 aluminum alloy by salt spray test, cyclic corrosion test, electrochemical experiment, scanning electron microscopy and energy dispersive X-ray spectroscopy. The results showed that AMXS6020 alloy had a higher corrosion resistance than AZ91D and ADC12 alloys. The superior corrosion resistance of AMXS6020 alloy was attributed to netlike eutectic structure consisting of (Al, Mg)2Ca and α-Mg, which could hinder the corrosion growth. The barrier effect of netlike (Al, Mg)2Ca phase structure on corrosion growth was also confirmed by potentiodynamic polarization.

Characterization and Analysis of Porosities in High Pressure Die Cast Aluminum by Using Metallography, X-Ray Radiography, and Micro-Computed Tomography.

Mechanical performance of cast aluminum alloys is strongly affected by the defects formed during solidification. For example, fractography studies of the fatigue specimens have shown that fatigue failure in aluminum castings containing defects is almost always initiated from defects, among which pores are most detrimental. However, elimination of these pores is neither always economically nor technically possible. This work characterizes defects in high pressure die cast aluminum alloy as an illustrative material, but the methods used can be applicable to other types of castings and defects. The defects were evaluated using metallography as well as micro-computed tomography techniques. The variability of defects between the specimens of two sizes as well as different porosity levels are studied statistically. The distributions of defects based on location within the specimens are also analyzed. Moreover, the maximum defect size within the specimens are estimated using extreme value statistics, which can be used as an input to fatigue life prediction models. Extreme value statistics is applied on both 2D and 3D defect data. The accuracy of each approach is verified by comparing the estimated maximum defect size within the specimens with the maximum observed defects on fracture surfaces of fatigue specimens.

Creep behavior of high-pressure die-cast AlSi10MnMg aluminum alloy

High-pressure die-cast (HPDC) AlSi10MnMg (AA365) has been widely used in the manufacturing of automotive components because it has excellent castability, is lightweight, and possesses good mechanical strength. In particular, this alloy must be capable of withstanding long-term exposure to high temperatures in order for these automobile parts to be useable. To investigate the viscoelastic behavior of HPDC AA365 with the aim of improving the long-term structural performance at high temperatures, we performed a creep test in the temperature range of 373–573 K with a constant applied stress of 64–217 MPa. A micro-hardness test of the HPDC AA365 alloy, performed after the creep test, yielded hardness values of 64.0 HV and 49.9 HV for the gauge and grip sections, respectively. The observed grain-size differences between the sections may have led to this difference in micro-hardness. Moreover, both values of micro-hardness were relatively low compared with the value of 93.5 HV for HPDC AA365 before the creep test. This was because of recovery and recrystallization. The creep tests also showed that the minimum creep rate increased with increasing applied stress for each temperature, causing a decrease in the time to failure. Based on the true stress exponent (n) on a scale of 1 to 90, various creep mechanisms for HPDC AA365 were revealed, including the Harper-Dorn, dislocation, and power-law breakdown mechanisms. The specific creep mechanism depended on temperature and applied stress. Furthermore, owing to the presence of the threshold stress, the apparent creep activation energy (259.08 kJ/mol) was substantially higher than that of aluminum (Al) self-diffusion (Qd = 143 kJ/mol). The existence of the threshold stress can also be demonstrated by a high n value that does not correspond to the n of pure Al under certain conditions. Failure in these alloys can be caused by void coalescence, cracked-brittle Si particles, and intermetallic phases that served to initiate and propagate the crack. Our results demonstrated that the fracture mechanism changed from transgranular to intergranular fracture in response to the applied stress and temperature. Our findings can improve the applications of high-pressure die-cast aluminum alloys.

Influence of welding parameters on electromagnetic supported degassing of die-casted and wrought aluminum

Laser beam welding of aluminum die casting is challenging. A large quantity of gases (in particular, hydrogen) is absorbed by aluminum during the die-cast manufacturing process and is contained in the base material in solved or bound form. After remelting by the laser, the gases are released and are present in the melt as pores. Many of these metallurgic pores remain in the weld seam as a result of the high solidification velocities. The natural (Archimedean) buoyancy is not sufficient to remove the pores from the weld pool, leading to process instabilities and poor mechanical properties of the weld. Therefore, an electromagnetic (EM) system is used to apply an additional buoyancy component to the pores. The physical mechanism is based on the generation of Lorentz forces, whereby an electromagnetic pressure is introduced into the weld pool. The EM system exploits the difference in electrical conductivity between poorly conducting pores (inclusions) and the comparatively better conducting aluminum melt to increase the resulting buoyancy velocity of the pores. Within the present study, the electromagnetic supported degassing is investigated in dependence on the laser beam power, welding velocity, and electromagnetic flux density. By means of a design of experiments, a systematic variation of these parameters is carried out for partial penetration laser beam welding of 6 mm thick sheets of wrought aluminum alloy AlMg3 and die-cast aluminum alloy AlSi12(Fe), where the wrought alloy serves as a reference. The proportion of pores in the weld seams is determined using x-ray images, computed tomography images, and cross-sectional images. The results prove a significant reduction of the porosity up to 70% for both materials as a function of the magnetic flux density.

The Role of Anodization in Naturally Cooled Heat Sinks for Power Electronic Devices

Abstract Effect of anodization on the thermal performance of naturally cooled heat sinks in power electronic devices made of die-cast aluminum alloy A380 and machined aluminum alloy 6061 was investigated experimentally and numerically. Various types of anodization were examined with different thickness of anodic aluminum oxide layer (AAO), pore size distributions, and surface coloring conditions. A customized natural convection and thermal radiation experimental chamber was built to measure the cooling capacity and heat sink temperatures. A 3D numerical model was also developed and validated against the collected data to provide more details into the contribution of the radiation heat transfer. The total emittance of the anodized samples was determined by a Fourier transform infrared reflectometer (FTIR) spectroscopy method. The results show a significant improvement in total hemispherical emissivity from 0.14 to 0.92 in anodized die-cast aluminum samples. This increase resulted in a considerable reduction in overall thermal resistance, up to 15%; where up to 41% of the total heat dissipation was contributed by thermal radiation. In spite of the rather distinguishable surface morphologies, the measurements suggested that thermal emissivity of the anodized die-cast Al A380 and Al alloy 6061 samples were in the same range.

Fluidity Test of Aluminum Alloy

A die to estimate the thickness of the thinnest fin of a heat sink made by die casting aluminum alloys is proposed. The die consists of a taper-off thin fin and a cooling area. It was shown that this die can be used to estimate the smallest fin thickness of different aluminum alloys.

Effects of Pouring Temperature on Microstructure and Mechanical Properties of the A356 Aluminum Alloy Diecastings

Abstract Diecastings of the A356 aluminum alloy were produced by rheo-diecasting (RDC) and High pressure die casting (HPDC), the microstructures of primary solidification, secondary solidification and eutectic Si of diecastings with different pouring temperature were explored and the mechanical properties of different parameters were tested. The result shows that the primary α-Al grains in RDC with self-inoculation method (SIM) are smaller and rounder than the dendrite structure in HPDC. During the RDC process, the amount of primary α-Al grains, average grain size and the lamellar spacing of the eutectic Si increase with the decrease of the melt treatment temperature. While the average grain size and the shape factor are gradually increasing with the increase of melt treatment temperature. As a result, RDC can significantly improve the mechanical properties of the A356 aluminum alloy compared with HPDC, the mechanical properties are optimal at 600°Cwith the tensile strength and elongation are 268.67MPa and 6.8%, respectively.

Microstructure evolution and mechanical properties of new die-cast Al-Si-Mg-Mn alloys

The microstructure evolution and mechanical properties of recently developed die-cast Al-Si-Mg-Mn alloys were investigated. CALPHAD modelling, based on the thermodynamic database, was carried out to design Al-Si-Mg-Mn alloys with different solid fractions of the eutectic mixture. Experimental results confirmed that the new Al-Si-Mg-Mn alloys have excellent yield strength of 230–280 MPa, ultimate tensile strength of 340–370 MPa and elongation to fracture of 2.3–4.3% from the standard tensile samples under as-cast condition. The as-cast microstructure consists of α-Al, α-AlFeMnSi, binary eutectic (Al + Mg2Si) and ultrafine quaternary eutectic (Si + α-Al + Mg2Si + π-AlFeMnSiMg). The high strength is induced by the formation of multi-scale eutectic mixtures and fine α-AlFeMnSi particles. The newly designed Al-Si-Mg-Mn alloys offer 20–50% increase in yield strength with good ductility, as compared with the commercially available die-cast aluminium alloys.

Advanced heat treated die-cast aluminium composites fabricated by TiB2 nanoparticle implantation

The global carbon emission reduction strongly requires high strength lightweight die-cast aluminium alloys in industry. Here die-cast AlSiMgMn–TiB2 composites with advanced mechanical performance were fabricated by the implantation of TiB2 nanoparticles. Super vacuum assisted high pressure die casting was applied to enable the T6 heat treatment of the composites, and the super vacuum of 20 mbar was achieved in the limited evacuation time of 1.6 s. The composites demonstrated good die castability within the addition of 3.5 wt% TiB2, while the composites could not fill into the chill vent with the addition of >3.5 wt% TiB2. The composite with 3.5 wt% TiB2 nanoparticles delivered the high hardness of 150.2 kg/mm2, yield strength of 351 MPa, tensile strength of 410 MPa, and the industrially applicable good ductility of 5.2%, after T6 heat treatment. The strengthening of the T6 heat treated composite was a result of both TiB2 nanoparticles and nanoscale β′′ precipitates that had coherent interfaces with α–Al matrix, i.e., Al(11-1)//TiB2(0001), Al[011]//TiB2[11-20], Al[320]//β″(a-axis), Al[1-30]//β″(c-axis) and Al(020)//β″(b-axis). The T6 heat treated composite reinforced by 3.5 wt% TiB2 showed ductile fracture.

High performance Al/TiB2 composites fabricated by nanoparticle reinforcement and cutting-edge super vacuum assisted die casting process

The structural lightweight in automotive and other industries motivates the usage of high strength die-cast aluminium alloys. However, the improvements of die-cast aluminium alloys are struggling limited by conventional micro alloying, and the improved yield strengths are still in the low level of 180–190 MPa. Here, high performance die-cast AlSiMgCu/TiB2 composite was fabricated through the reinforcement of TiB2 nanoparticles and the latest developed cutting-edge super vacuum assisted high pressure die casting (HPDC) process. The composite with 3.0 wt% TiB2 nanoparticles could deliver the milestone high hardness of 1.56 GPa, yield strength of 356 MPa, tensile strength of 457 MPa and an industrially applicable ductility of 5.5%. The composite was strengthened by TiB2 nanoparticles and nanoscale Q′ and θ′ precipitates that all had highly coherent interfaces with the α–Al matrix, indicative of strong interfacial bonding. The implantation of TiB2 nanoparticles also induced special grain refinement strengthening of the composite. The fabricated composite demonstrates ~90% increase in strength over the currently available alloys, and it is promising for industrial application.

Hybrid joints of die-casted aluminum/magnesium by ultrasound enhanced friction stir welding (USE-FSW)

As consistent lightweight construction nowadays becomes more and more important in smart production processes, the demand for joints of dissimilar materials increases steadily due to their variety of advantages in engineering. Friction stir welding (FSW) is an innovative pressure welding technique, which offers the ability to realize such dissimilar joints while achieving high tensile strengths. Furthermore, it has been proved that ultrasound enhanced friction stir welding (USE-FSW) has an additional positive effect on the joint strength of these compounds due to the additional introduction of mechanical energy into the joining zone through influencing the formation of brittle intermetallic phase (IMP) and particle allocation in the weld nugget. In this paper, the influence of power ultrasound introduction via USE-FSW on hybrid joints of industrially die-cast aluminum alloy EN AC-48000 (AlSi12CuNiMg) and magnesium alloy AZ91 (MgAl9Zn1) has been investigated. Besides mechanical testing, light microscopic and scanning electron microscopic investigations (SEM) as well as differential scanning calorimetry have been conducted. Furthermore, corrosion behavior of the base material and X-ray radiographic images of FSW and USE-FSW joints have been examined. Additionally, the influence of different ultrasound powers and changes in the introduction side on the tensile strength and microstructure of the joints has been investigated.

Correlation between segregation behavior and wall thickness in a rheological high pressure die-casting AC46000 aluminum alloy

The segregation behavior of a rheological high pressure die-casting (Rheo-HPDC) AC46000 aluminum alloy at positions with different wall thicknesses was studied. The results reveal that positions with different wall thicknesses exhibit different cooling rates that can result in distinctly different segregation characteristics. Segregation results in varying microstructure, elemental distribution, and hardness along the thickness of an alloy. The segregation in a Rheo-HPDC AC46000 alloy can be categorized as: cross-sectional segregation along the thickness and center segregation. As the distance from the alloy surface increases, the volume fraction of the primary phase increases, and the hardness of the microstructure and content of the eutectic Al-Si, Al2Cu, and α-(FeMn)3Si2Al15 phases decrease. As the alloy wall thickness increases, the differences in the volume fraction of the primary phase, elemental content, and hardness of the microstructure between the edge and center gradually decrease. Compared with the normal center microstructure, the volume fraction of the primary phase in the center segregation microstructure is lower, and the morphology is not round. The content of the eutectic Al-Si, Al2Cu, α-(FeMn)3Si2Al15, and Si phases is higher, and these phases are nonuniformly distributed. Center segregation is often accompanied by shrinkage cracks. As the alloy wall thickness increases, the center segregation area and crack size increase, and the more hard–brittle α-(FeMn)3Si2Al15 particles accumulate the crack. The hardness of the center segregation structure is higher than that of the normal center structure. With increasing alloy wall thickness, the hardness of the center segregation microstructure first increases and then decreases.

Mechanical and Fatigue Properties of Gravity Die-Cast A356 Aluminium Alloy with Addition of Scandium

A356 is widely used for the casting of high strength components in automotive, aerospace and other industrial applications. This is due to its high achievable strength, castability, light weight, good thermal and electrical conductivity. However, the as-cast A356 exhibits relative poor mechanical properties due to the presence of coarse acicular eutectic silicon morphology. In this study, Sc-modified-A356 and the effect of heat treatment have been studied and compared with unmodified A356. Various amounts of Sc ranging from 0.2 wt% to 0.6 wt% were added into the mixture of A356 aluminium alloy and the specimens were produced by using gravity die-casting. Next, the ultimate tensile strength, Vickers hardness and fatigue behaviour of the cast samples are examined. The results revealed that by adding 0.4 wt.% of Sc, the heat treated sample is able to achieve ultimate tensile strength of above 300 MPa and Vicker’s hardness of 118 HV. Furthermore, the fatigue properties of the 0.4 wt% Sc-A356 with T6 heat treatment was found to be improved as compared to the unmodified A365 samples.

The formation of Al6 (Fe, Mn) phase in die-cast Al-Mg alloys

In aluminium alloys, iron is a common impurity as it is unavoidably picked up in practice. The excessive Fe is strongly prone to form various intermetallic phases. These Fe-rich intermetallics are generally brittle and act as stress raisers to weaken the coherence with Al matrix, therefore decreasing elongation. However, Fe addition in Al-Mg alloys may be beneficial because of the improvement in the yield strength with the scarification of ductility of die-cast aluminium alloys. The morphology of intermetallic phases has a vital effect on the properties of aluminium alloys. In the present work, the 3D morphology of Al6 (Fe, Mn) in die-cast Al-Mg-Mn alloys with different levels of Fe contents were revealed. The formation of Al6 (Fe, Mn) was also studied through crystal features and solidification behaviours.

Effect of rare earth elements on the microstructure and properties of a die-cast aluminum alloy

Abstract The effects of the rare earth elements Ce, La and Sm on the microstructure and mechanical properties of a die-cast aluminum alloy were studied. First, the optimal percentage content of the main elements in the alloy was determined by a single factor and by orthogonal experiments based on the composition range of ADC12 aluminum alloy. The results showed that the optimal percentage content of the main elements in ADC12 die-cast aluminum alloy were 11 wt.-% Si, 2.5 wt.-% Cu, 0.5 wt.-% Mn and 0.3 wt.-% Mg. The tensile strength was 285 MPa and the fracture strain 2.23 %. Then, three rare earth elements of varied contents were added to the above-mentioned aluminum alloy. The tensile strength and elongation of the alloy were increased through the addition of rare earth elements. The comprehensive mechanical property of the alloy was best when Ce, La and Sm levels were at 0.6, 0.4 and 0.2 wt.-%, respectively, in the single factor test. Sm had the largest influence on the comprehensive mechanical properties of the alloy, followed by Ce and La which had the least influence.

Defect Susceptibility of Tensile Properties to Microporosity Variation in High-Pressure Die-Cast Aluminium Alloy Controlled by Gas Bubbling Flotation Treatment

This study aims to investigate the variability in the tensile properties of high-pressure die-cast aluminium alloy controlled by the gas bubbling filtration or flotation (GBF) process in terms of the defect susceptibility of tensile properties to the variation in the overall microporosity level, including bifilm oxide and pre-existing microvoids. Test specimens were fabricated by adopting a high-pressure die-cast process of the cold chamber type at the production scale using A384.0 aluminium alloy. The volumetric porosity of cast specimens gradually decreased with GBF treatment, even though the fractographic porosity tended to decrease only under a specific GBF condition, with a remarkable microstructural refinement. The degassing treatment of 5 min could achieve a remarkable grain refinement, and further, this optimal condition could induce a practical improvement in the defect susceptibility of tensile properties to microporosity variation as well as the nominal level of tensile properties. The main reason for grain refinement in GBF treatment is the dispersion of small-sized pro-eutectic solid particles by fragmentation of abnormally big-sized dendrites, which are preferentially formed by an undercooling effect in a region around the impeller and gas inlet. Additionally, the improvement in melt quality by degassing action for dissolved hydrogen gas is practically nullified through the coarsening of pro-eutectic solid particles as well as the additional inclusion of bifilm oxide by excessive GBF treatment.

Porosity reduction in the laser beam welding of aluminium die cast alloys through the overlapping of mechanically induced sound waves

In recent years, to meet society’s increasing demands to reduce environmental pollution, the industry’s attention has been drawn to the subject of lightweight construction. Especially die-cast aluminium alloys offer their user a variety of design options for targeted weight reduction. However, a problem with the use of this material is the cohesive connection using welding technology. The main problem are the release agent residues as well as gas and oxide residues, trapped in the die-cast, which diffuse during the welding process in the direction of the liquid aluminium melt and result in a weld porosity. Due to the high heating and cooling rates resulting from the laser beam welding and the resulting outgassing possibilities of the liquid melt, the process of laser beam welding is particularly susceptible to the joining of aluminium die-cast components and, despite its many advantages, can currently only be used by complex and expensive additional measures. This is where the research activities of the Department for Cutting and Joining Manufacturing Processes (tff) start. The department deals with a specific influence on the prevailing melt flow through a sound wave superposition during the welding process. For the coupling of the sound waves, flexibly positionable piezoshakers are used, which allow greater degrees of freedom with respect to the welding geometry.

A Tool for Predicting the Effect of the Plunger Motion Profile on the Static Properties of Aluminium High Pressure Die Cast Components

The availability of tools for predicting quality in high pressure die casting is a challenging issue since a large amount of defects is detected in components with a consequent worsening of the mechanical behavior. In this paper, a tool for predicting the effect of the plunger motion on the properties of high pressure die cast aluminum alloys is explained and applied, by demonstrating its effectiveness. A comparison between two experiments executed through different cold chamber machines and the same geometry of the die and slightly different chemical compositions of the alloy is described. The effectiveness of the model is proved by showing the agreement between the prediction bounds and the measured data. The prediction model proposed is a general methodology independent of the machine and accounts for the effects of geometry and alloy through its coefficients.

Erozijska obraba oksidiranih in nitriranih plasti površine jeklenega orodja med tlačnim litjem aluminijeve zlitine

Erozijska obraba oksidiranih in nitriranih plasti površine jeklenega orodja med tlačnim litjem aluminijeve zlitine