No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Vacuum assisted high pressure die casting of aluminum alloys
Abstract
High pressure die castings usually contain gas porosity due mainly to the entrapment of air or gas in the melt during the very high speed injection of the molten metal into the cavity. In this paper, the advantages of using an evacuated die cavity during mould filling were evaluated. ASTM standard die casting tensile specimens of three Al alloys, Al–5%Si, Al–8%Si and Al–18%Si, were cast on a Buhler shot control die casting machine equipped with a Fondarex vacuum assist system. The effect of vacuum assistance on the porosity distribution and mechanical properties of the produced castings were studied in detail. Selected specimens were also subjected to a T6 tempering treatment to evaluate the formation of surface blisters and effects on the mechanical properties.It was found that the volume of gas porosity and the pore sizes in the castings were significantly reduced by using vacuum assistance during die casting. As a result, the density and the mechanical properties, particularly the tensile strength and ductility, were improved markedly. An optimum injection speed was also identified for producing high performance castings. After heat treatment, vacuum assisted die cast parts showed much less surface blistering when compared to conventional die cast parts, demonstrating that vacuum assisted die castings are promising for heat treatment at elevated temperatures to improve the mechanical properties.
... However, the entrapped air is more difficult to control and a major source of gas porosity in HPDC, since air is entrapped during the turbulent flow of molten metal filling the cavity at high velocities. [6][7][8] Vacuum die casting is an improvement on the traditional HPDC process, where vacuum is implemented to evacuate the air in the injection chamber (shot sleeve) and die cavity during metal injection. The vacuum minimizes the amount of air in the die cavity to reduce the potential for air entrapment during filling. ...
... The vacuum minimizes the amount of air in the die cavity to reduce the potential for air entrapment during filling. 7,9,10 Many researchers have studied the effect of different vacuum levels on entrapped air 7,11 and porosity in castings. [12][13][14] Hu et al. 15 studied the effect of vacuum levels on the ductility and amount of porosity in castings. ...
... The vacuum minimizes the amount of air in the die cavity to reduce the potential for air entrapment during filling. 7,9,10 Many researchers have studied the effect of different vacuum levels on entrapped air 7,11 and porosity in castings. [12][13][14] Hu et al. 15 studied the effect of vacuum levels on the ductility and amount of porosity in castings. ...
High pressure die casting (HPDC) of aluminum alloys is increasingly used for thin-walled and lightweight components in automotive and other industries. However, a major concern associated with these castings is gas porosity mostly attributed to air entrapment during the filling process of the high-speed metal injection in HPDC. One approach to reduce gas porosity is to use a vacuum to remove air from the die cavity during the filling process and improve the mechanical properties of the HPDC components. However, quantitative effect of vacuum on porosity formation and fluid flow during die casting has not been sufficiently established to maximize the benefits of vacuum use in the die casting industry. In this paper, water analog experiments were conducted to investigate the effect of vacuum on die cavity fill and porosity formation. The results were compared to MAGMASOFT® flow simulations and X-ray Computed Tomography (CT) scans of HPDC aluminum alloy castings to quantify the reduction of entrapped air and gas porosity at different levels of vacuum. The water analog experiments and simulations show good agreement and demonstrated quantitative benefits of using vacuum in high pressure die casting.
... AlSi10Mg alloys have been widely used in high-pressure die casting (HPDC) to produce highly integrated structural components for automotive and aerospace industries owing to their excellent castability, high strength-to-weight ratio, and good corrosion resistance [1,2]. The cooling rates of HPDC are relatively high, generally on the order of 10 2 -10 3 °C/s [3]. ...
... T5 heat treatment, which provides artificial aging at low temperatures, is still preferable in the industry owing to its low cost as well as low risk of blistering and distortion in complex and thin-walled die castings [1,2,4,5]. However, the low ductility remains an unsolved problem in T5-treated die castings despite their excellent tensile strengths. ...
The precipitation microstructures in both primary α-Al and eutectic Al and mechanical properties of high-pressure vacuum die-cast AlSi10MgMn alloy under T5 aging treatments were systematically investigated. The results revealed that the three T5 treatments (peak aging, pre-aging, and prolonged aging) achieved similar levels of yield strength (YS) but different elongations (El). The El values of the T5-treated samples were effectively improved by pre-aging and prolonged aging. The best strength-ductility trade-off was achieved by prolonged aging at 185 °C for 24 h, providing a YS of 225 MPa and an El of 6.8%. Compared to the T6-treated samples, the El of the T5 prolonged-aged samples was 20% higher, but the YS was 15% lower. The microstructures after T5 primarily comprised nano-sized Si particles, Si clusters, and β″ precipitates in primary α-Al, but only Si clusters and β″ precipitates in eutectic Al. Si particles were the main and most stable strengthening phases. The T6-treated samples predominantly contained β″ precipitates in both primary and eutectic Al. The different precipitates in the primary and eutectic Al were quantified, and their strengthening contributions were analyzed by applying classical shearing and bypassing mechanisms. The predicted overall YS values are in good agreement with the experimental data.
... Figure 1 displays a typical tension clamp fracture during a tensio test and illustrates the microstructure of the faults. Because of gas problems, ordinary die castings result in elongation not being hig enough; therefore, high-vacuum die-casting (HVDC) technology has received wide atte tion [16][17][18]. HVDC offers benefits, such as decreased porosity, improved surface qualit and higher elongation rates, while maintaining the same production efficiencies as co ventional die casting. Moreover, it can enhance eutectic silicon morphology and genera Because of gas problems, ordinary die castings result in elongation not being high enough; therefore, high-vacuum die-casting (HVDC) technology has received wide attention [16][17][18]. ...
... HVDC offers benefits, such as decreased porosity, improved surface qualit and higher elongation rates, while maintaining the same production efficiencies as co ventional die casting. Moreover, it can enhance eutectic silicon morphology and genera Because of gas problems, ordinary die castings result in elongation not being high enough; therefore, high-vacuum die-casting (HVDC) technology has received wide attention [16][17][18]. HVDC offers benefits, such as decreased porosity, improved surface quality, and higher elongation rates, while maintaining the same production efficiencies as conventional die casting. Moreover, it can enhance eutectic silicon morphology and generate precipitation reinforcement through heat treatment, thereby further improving toughness. ...
To enhance the performance of ultra-high voltage power fittings in severe weather conditions without altering their current structure, the high-strength and toughness aluminum alloys were rationally selected to study the optimization of the die-casting process. This approach aims to improve the overall longevity and function of the power fittings in extreme climates. First of all, the propose of this study is to use the material’s strength–toughness product (STP) concept to evaluate the material stability of the power fitting impact resistance and fatigue toughness in order to determine the appropriate material selection. Secondly, the location of the mold’s sprue and gate was optimized through finite element simulation to prevent gas volume and flow defects during the casting process. This improves the material’s toughness and anti-fatigue failure characteristics of the product. Then, vacuum equipment and a vacuum valve auxiliary system were added based on the existing die-casting machine, and the mold structure was optimized to enable the vacuum die-casting process. Finally, a water-based boron nitride environmentally friendly mold release agent was used to solve demolding difficulties with an A356 aluminum alloy and improve mold lubrication and surface quality. The production of quad-bundled spacers using A356 and vacuum die casting has resulted in parts with a tensile strength of at least 250 MPa and an elongation of no less than 7%. This improvement has laid a foundation for enhancing the operational reliability of existing overhead transmission line fittings.
... Vacuum-assisted high-pressure die casting (VHPDC) has been studied with the main purpose of reduction of entrapped air and quantities of oxide films in the cast. This is done by applying a low atmospheric pressure in the shot sleeve and cavity during injection and filling [36]. With applying vacuum, some process parameters are altered, such as the filling time, which tends to be faster. ...
... Thus, the main differences were porosity levels and thus increased casting integrity. Reducing trapped air allows the application of heat treatment to the cast without causing the blister defects mentioned above [36]. The pores tended to be fewer and smaller, with a decrease in volumetric porosity, from 0.34 to 0.09%, and were distributed more evenly with VHPDC. ...
Low- pressure casting and high-pressure casting processes are the most common liquid-based technologies used to produce aluminum components. Processing conditions such as cooling rate and pressure level greatly influence the microstructure, mechanical properties, and heat treatment response of the Al alloys produced through these casting techniques. The performance of heat treatment depends on the alloy’s chemical composition and the casting condition such as the vacuum required for high-pressure casting, thus, highlighting the low-pressure casting application that does not require a vacuum. The level of pressure applied to fill the mold cavity can affect the formation of gas porosities and oxide films in the cast. Moreover, mechanical properties are influenced by the microstructure, i.e., secondary dendritic arm spacing, grain size, and the morphology of the secondary phases in the α-matrix. Thus, the current study evaluates the most current research developments performed to reduce these defects and to improve the mechanical performance of the casts produced by low- and high-pressure casting.
... Though the alloys find their applications in a wide spectrum of industries, they face many limitations and at times fail prematurely. Some of the reasons for premature failure are (a) the lack of required properties in metal alloys (low hardness, low melting point susceptible to stress corrosion cracking) [3], (b) the adverse effect of alloying elements [4], (c) the residual stresses, porosity, and dendritic structure of cast products (the defects that are formed during the manufacturing processes) [5], and (d) the cracks caused by residual stresses or cold shuts in the component during solidification and cooling [6]. Porosity is a severe defect found commonly in pressure die casting (PDC) due to turbulence in injected molten metal and poses a severe problem in the case of pressure vessels as well as structural members [7]. ...
... The optimum temperature for annealing is determined by the hardness test. In order to remove the residual stress in the uncoated and coated specimens, the specimens of size 2 × 5 × 0.2 cm 3 were annealed at 300°C for 8 h [6,13,16] and the hardness values were determined as per the ASTM-E-384 standard with 100 g load using Vickers' hardness testing equipment. ...
The aluminum (Al) alloy AA7075 is widely used in various industries due to its high strength-to-weight ratio, which is comparable and replaceable to steel in many applications. However, it has poor resistance to wear and corrosion compared to other Al alloys. The conventional pressure die coating with Cr and cadmium has led to premature failure while the load is applied. It is indeed to develop a novel coating method to improve the mechanical, wear, and corrosion properties of AA7075 Al alloy. In the present investigation, the binary and ternary metals such as zinc–nickel (Zn–Ni), zinc–cobalt (Zn–Co), and nickel–chromium–cobalt (Ni–Cr–Co) are electroplated on the substrate material (AA7075). In order to ensure optimal coating adhesion, the surface of the substrate material was pre-treated with laser surface treatment (LST). The mechanical and corrosion studies have been carried out on the uncoated and coated materials. It is observed from the findings that the ternary coating has higher wear resistance than the binary-coated material. The ternary coating has 64% higher resistance in the non-heat-treated status and 67% higher resistance in the heat-treated condition compared to the uncoated specimens. The tensile strength (MPa) of Ni–Cr–Co on AA7075 pressure die casting (PDC) is higher than the other deposits (582.24 of Ni–Cr–Co > 566.07 of Zn–Co > 560.05 of Zn–Ni > 553.64 of uncoated condition). The presence of a crystalline structure with the high alignment of Co and Ni atoms could significantly improve the corrosion resistance of Ni–Cr–Co coatings on AA 7075 PDC substrates when compared to binary coatings. The scanning electron microscopy (SEM) images, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy findings on the coated materials have been corroborated with the analyses on mechanical and corrosion properties. The XRD analysis of the Zn–Ni binary coating has reported that the diffraction peaks of γ-NiZn3 (831), γ -Ni2Zn11 (330), and 631 with 2θ values 38, 43, and 73° are confirming the presence of Zn–Ni binary deposit on AA7075 PDC substrate. The XRD pattern of Zn–Co-coated material has revealed that the presence of three strong peaks such as Zn (110), Co (111), and CoZn (211) and two feeble peaks such as ε-CoZn3 (220) and ε-CoZn3 (301) are clearly visible. The XRD pattern of Ni–Cr–Co ternary coating has exhibited that the Ni–Cr–Co ternary deposit is a solid solution with a body-centered cubic structure due to the formation peaks at lattice plane such as (110), (220), and (210) with a crystal lattice constant of 2.88 A°. The SEM image for both the binary- and ternary-coated materials has exhibited that the deposited surface has displayed many shallow pits due to hitting by progressive particles. The SEM image has illustrated the presence of Zn–Ni atoms with smaller globular structure. The surface morphology of binary Zn–Co coating on the PDC AA7075 substrate has unveiled the evenly distributed dot-like structure and submerged Co particles in the galaxy of Zn atoms. To understand the effectiveness of bonding by laser texturing, cross-section SEM has been carried out which furthermore revealed the effective adhesion of Ni–Cr–Co on AA7075 PDC; this could also be the reason for the enhancement of microhardness, wear, and corrosion resistance of the said coating.
... Advancements in the HPDC process include the addition of vacuum pressure to extract the extra entrapped air that leads to the porosity and poor mechanical properties of the components. Figure 3e shows a simplified schematic of the vacuum-assisted HPDC (VA-HPDC) process [76], where the vacuum pressure can range from 60-3000 mbar. This ensures no remaining gas within the melt after solidification, which enables stable solution-treated products. ...
... (d) Wax pattern tree for investment casting [70]. Schematic of (e) vacuum-assisted high-pressure die-casting [76], and (f) typical anti-gravity low-pressure die-casting arrangement [88]. (g) Schematic of direct squeeze casting [102]. ...
While research on lightweight materials has been carried out for decades, it has become intensified with recent climate action initiatives leading pathways to net zero. Aluminum alloys are at the pinnacle of the light metal world, especially in the automotive and aerospace industries. This review intends to highlight recent developments in the processing, structure, and mechanical properties of structural Al-Si alloys to solve various pressing environmental issues via lightweighting strategies. With the excellent castability of Al-Si alloys, advancements in emerging casting methods and additive manufacturing processes have been summarized in relation to varying chemical compositions. Improvements in thermal stability and electrical conductivity, along with superior mechanical strength and fatigue resistance, are analyzed for advanced Al-Si alloys with the addition of other alloying elements. The role of Si morphology modification, along with particle distribution, size, and precipitation sequencing, is discussed in connection with the improvement of static and dynamic mechanical properties of the alloys. The physics-based damage mechanisms of fatigue failure under high-cycle and low-cycle fatigue loading are further elaborated for Al-Si alloys. The defect, porosity, and surface topography related to manufacturing processes and chemical compositions are also reviewed. Based on the gaps identified here, future research directions are suggested, including the usage of computational modeling of microstructures and the integration of artificial intelligence to produce mass-efficient and cost-effective solutions for the manufacturing of Al-Si alloys.
... This technique, however, generates intrinsic flaws, such as gas porosity in the resulting castings, which happens primarily due to the trapping of air in the molten metal as a result of the high-speed injection of liquid metal into the die chamber. Pores in casting are commonly identified as gas porosity and shrinkage porosity, which are detrimental as their presence negatively affects mechanical characteristics and pressure resistance [6][7][8]. Al series alloys, particularly Al-Si alloys, such as Al-Si-Cu and Al-Si-Mg, are extensively employed in the HPD industry because they have a distinctive combination of desired properties (high strength-to-weight ratio, high thermal and electrical conductivity, good formability, distinct corrosion behavior, and recycling potential) that are necessary in ...
Near-net-shaped metal products manufactured by high-pressure diecasting (HPD) encountered more or less critical failure during operation, owing to the development of micro-defects and structural inhomogeneity attributed to the complexity of geometrical die design. Because the associated work primarily relies on technical experience, it is necessary to perform the structural analysis of the HPDed component in comparison with simulation-based findings that forecast flow behavior, hence reducing trial and error for optimization. This study validated the fluidity and solidification behaviors of a commercial-grade Al-Si-Cu-Mg alloy (ALDC12) that is widely used in electric vehicle housing parts using the ProCAST tool. Both experimental and simulation results exhibited that defects at the interface of a compact mold filling were barely detected. However, internal micro-pores were seen in the bolt region, resulting in a 17.27% drop in micro-hardness compared to other parts, for which the average values from distinguished observation areas were 111.24 HV, 92.03 HV, and 103.87 HV. The simulation aligns with structural observations on defect formation due to insufficient fluidity in local geometry. However, it may underestimate the cooling rate under isothermal conditions. Thus, the simulation used in this work provides reliable predictions for optimizing HPD processing of the present alloy.
... These characteristics contribute to the effective manufacturing of products with complex shapes, leading to an expanded use of aluminum alloys in various sectors including aerospace, transportation equipment, and electronics [3]. maintaining a vacuum state within the mold throughout the casting process, thus requiring a high level of operator skill and substantial investment in specialized facilities [14][15][16][17][18][19]. ...
This study aims to investigate the role of oxygen in optimizing the Pore-Free Die Casting (PFDC) process to enhance the quality of aluminum castings by minimizing porosity defects. The effects of oxygen levels on the integrity of high pressure die casting specimens was investigated by injecting oxygen at different durations (1 s, 3 s, and 5 s) through air jet valves installed at the mold cavity. The CT results indicate that increasing the oxygen injection time significantly reduces the porosity volume from 0.9 to 0.18%, with smaller defects in size as well. Notably, after applying the PFDC process, the elongation improved from 2.23 to 4.58%, suggesting that replacing atmosphere in the cavity space with oxygen plays a crucial role in enhancing the mechanical properties of the HPDC specimens. The improvement is believed to be caused by promoting oxidation reactions with the high concentration of oxygen, which leads to a decrease in gas entrapment during the casting process.
... superior to HPDC in reducing porosity, minimizing blisters, improving surface finish, and enhancing mechanical and dynamic properties [23][24][25][26][27][28][29][30][31] . Despite advancements in casting technology, the complete elimination of pores remains a significant challenge. ...
Utilizing lightweight Al alloys in various industrial applications requires achieving precise pressure tightness and leak requirements. Vacuum pressure impregnation (VPI) with thermosetting polymers is commonly used to address leakage defects in die-cast Al alloys. In this study, the efficacy of the VPI technique in sealing alloy parts was investigated using a combination of nondestructive micro X-ray computed tomography (micro XCT) and a standard leak test. The results demonstrate that the commonly used water leak test is insufficient for determining the sealing performance. Instead, micro XCT shows distinct advantages by enabling more comprehensive analysis. It reveals the presence of a low atomic number impregnates sealant within casting defects, which has low grey contrast and allows for visualizing primary leakage paths in 3D. The effective atomic number of impregnated resin is 6.75 and that of Al alloy is 13.69 by dual-energy X-ray CT. This research findings will contribute to enhancing the standard VPI process parameters and the properties of impregnating sealants to improve quality assurance for impregnation in industrial metals.
... Whereas the energy required for the production of secondary alloys is less than 5% of what needed for primary production (0.5-0.75 kWh/ kg), resulting in a cheaper and more environmentallyfriendly process. 1 High-Pressure Die Casting (HPDC) has been applied to produce extremely thin-walled components that can be used for parts for the automotive industry. 2 This process can be assisted by a vacuum to reduce casting defects, specifically porosity. 3 Conventional HPDC alloys are typically secondary aluminum alloys in which iron is intentionally maintained within the range of 0.8-1.1 wt% to prevent soldering of molten metal to the die. ...
In the present study, a predictive analysis was performed to investigate the effect of droplet size, section size and type of the primary and secondary AlSi10MnMg alloys manufactured by vacuum-assisted high pressure die casting on wettability of the cast samples with water, since wettability influences corrosion resistance. Additionally, corrosion resistance of samples was studied using a linear polarization experiment. Contact angle (CA) measurements were performed on the specimens using a goniometer. An Artificial Neural Network was then developed to predict the contact angle values as a function of the predictor variables. The developed model was able to predict unseen CA values with excellent accuracy with the Pearson correlation coefficient of 0.96 between the predicted and observed CA. The modeling results show that the type of alloy (primary or secondary) is the most significant factor affecting CA, where almost 80% of CA variation is the result of changing the type of alloy. Confocal microscopy images demonstrate that this is attributed to the change in the heterogeneity of the surface, which affects contact angle values. The corrosion studies reveal that corrosion resistance is dependent on the type of alloy and surface roughness. The primary alloy possesses more corrosion resistance than the secondary alloy. This is due to the larger fraction of intermetallic compounds in the microstructure of the secondary alloy, which serve as galvanic sites in the corrosion reaction accelerating corrosion rate. Moreover, the non-uniformity induced by larger surface roughness is detrimental to the corrosion resistance of the samples. These results indicate that the data-driven approach used in this research is very promising not only to predict the performance, but also to optimize and design high-performance corrosion resistant surfaces of cast aluminum alloys.
... Research in alloy development has pinpointed certain HPDC aluminum alloy compositions, such as Silafont, Castasil, Aural, etc., characterized by superior mechanical characteristics (Samanta et al., 2022). Similarly, advancements in die-casting techniques, specifically vacuum-assisted HPDC, have played a role in minimizing casting flaws, such as porosity (Niu et al., 2022) However vacuum-assisted HPDC process is costly. ...
A key challenge in the production of high-grade automotive aluminum components through the High-Pressure Die Casting (HPDC) process is the imperative to minimize imperfection. In addressing this concern, this study utilizes friction stir processing (FSP), a widely recognized intense plastic deformation technique. FSP is applied to systematically alter the microstructure of HPDC Al-4Mg-2Fe, a prominent alloy extensively used in the die-casting sector. By using the pass strategy to incorporate both one-pass and two-pass approaches, the microstructure is selectively altered to establish a defect-free processed zone. The utilization of FSP demonstrates its efficacy in breaking aluminum dendrites and acicular silicon particles, leading to a uniformly dispersed arrangement of equiaxed silicon particles within the aluminum-based matrix. In addition, FSP eradicates porosity and disintegrates needle-like Fe particles, resulting in a more refined and homogeneously distributed structure. Subsequently, the material's mechanical properties processed by FSP were assessed in the longitudinal direction concerning the processing axis and then compared with those of the original base material. The microstructural refinement and reduction in porosity induced by FSP result in a notable enhancement in hardness, with an increase of 23% after one pass and 37% after two passes. The substantial improvement in mechanical properties during the FSP process is predominantly attributed to modifications in the morphology, refinement, and dispersion of intermetallic particles within the matrix. This improvement is further complemented by the ultrafine dispersion of casting defects. This study underscores the efficacy of FSP as a valuable tool for modifying microstructures and improving mechanical properties in HPDC Al-4Mg-2Fe alloys. Such advancements align with the lightweighting objectives pursued by the automotive industry.
... Cast aluminum alloys are manufactured using a process called casting, which involves melting the aluminum and pouring it into a mold to solidify [14]. There are several methods of casting aluminum, including sand casting [15], die casting [16], investment casting [17] and permanent mold casting [18]. Wrought aluminum alloys are manufactured using a process called deformation, which involves shaping the metal while it is in a solid state [19,20]. ...
... The internal porosity of the samples was evaluated using X-ray computed tomography (CT; Nikon, XTH320L, Ulsan, Republic of Korea) [23,24]. To evaluate the mechanical properties of the samples, the tensile strength was evaluated (Instron, 5989, Ulsan, Republic of Korea); a hardness test (Matsuzawa, PMT-X7, Ulsan, Republic of Korea) and fractographic examination were performed on the tensile test specimens [30][31][32]. Figure 4 shows images of the as-cast A383 alloy and CNT-added composites cast using a single gate and poly gate. The as-cast state consisted of cavities (places where the composites were cast), a runner, vent, overflow, gates and biscuit. ...
A383 Al-Si-Cu alloy matrix composites were reinforced with different amounts (0.5, 1.0, 1.5 and 2.0 wt%) of chopped multiwalled carbon nanotubes (MWCNTs) and fabricated using the oxygen-replacing die casting (ORDC) process to reduce gas porosities via the reaction of molten Al and O2 replaced in the mold cavity. MWCNTs were added to the mold cavity by supplying O2 and using a poly gate in the ORDC mold to improve CNT dispersity in the matrix of the composite. Microstructure studies of the composites showed a uniform CNT distribution within the matrix and grain refinement. X-ray computed tomography images showed that the internal porosities were affected by the CNT addition amount and gate type used in the mold, and Raman spectroscopy analysis indicated that CNTs in the matrix were free of significant defects. The 1.0 wt% CNT-added composite cast using the poly gate showed the highest ultimate tensile strength of 258.5 ± 5.2 MPa and hardness of 157.9 ± 3.0 Hv; these values were, respectively, 21% and 30% higher than those of the monolithic A383 alloy, confirming the feasibility of fabricating the MWCNT-added A383 alloy composite with a poly gate using the ORDC process.
... Too much lubricant on the die does not evaporate from the surface before the injection, increasing gas porosity. The second important thing is a properly working vacuum system that eliminates gases in the die cavity [19]. Finally, the shot profile setting should be correct in avoiding air entrapment in the shot sleeve and mold temperature indirection to reduce the solidification rate in this cold area. ...
... Improvements in die-casting technology (vacuum-assisted HPDC method and high vacuum die-casting method) help in reducing casting defects such as porosity [5]. Alloy chemistry is often altered to improve mechanical properties. ...
Steadily rising demand for glider weight reduction has driven the development of vacuum-assisted high-pressure die-cast (HPDC) Al alloys for automotive structural components. Aural-5 is a strontium-modified HPDC alloy utilizing manganese (Mn) to reduce die soldering, eliminating detrimental needle-shaped Fe-bearing β-phase intermetallic and improving ductility. HPDC Aural-5 contains shrinkage porosity, dendrites with Al-Si eutectic colonies, externally solidified crystals (ESCs), shear/band structure, and large second-phase particulates. Porosity, ESCs, and large second-phase particles work as crack initiation sites, negatively impacting tensile properties. In this study, friction stir processing (FSP) is employed for microstructural modification of a thin-walled HPDC Aural-5 by eliminating porosity and breaking down dendrites, second-phase particles, eutectic colonies, ESCs, and shear/band structures to create wrought microstructure with homogenized particle distribution. Mechanical property characterization indicates ~30 and ~35% enhancement in yield strength and ductility and associated marked effects on ~69% improvement in tear toughness according to the ASTM B871 test.
... Al-Si based alloys have been successfully used for HPDC applications due to their good fluidity and excellent castability [6][7][8]. Besides, the addition of other alloying elements, such as Cu, Mg, Mn, Sr and Ti [9][10][11][12], can improve the performance of the castings, including corrosion resistance and fatigue properties [13][14][15]. 2 Presently, the Al-Si-Mg alloy system has been widely used in the die casting industry [16]. ...
... The defects observed in the production of AM-assisted cast lattices are typical of the investment casting process in general. For example, the presence of gas porosity is justified by the entrapment of air or gas in the melt during the very high-speed injection of the molten metal into the cavity [29] . Despite using vacuum-assisted casting, the presence of gas porosity was not entirely eliminated. ...
The current work analyzes the process-microstructure-mechanical property relationship of metallic lattices manufactured through AM-assisted investment casting and powder bed fusion (PBF) techniques. For the analysis, both solid- and sheet-network-based gyroid lattices are manufactured, using AlSi10Mg alloy as base material. Micro-tomography and scanning electron microscopy are employed to assess the differences in the as-built structure quality in each design case, identifying method caveats and quantifying differences in the distribution and magnitude of the lattice's inner porosity. Moreover, their nonlinear compressive mechanical performance is experimentally probed to assess the elastic stiffness, peak, plateau stress, as well as overall energy absorption in each case. Results indicate higher elastic stiffness and peak stress for the PBF-manufactured specimens irrespective of the lattice topology and overall comparable stress and energy absorption properties. However, in contrast to PBF specimens, AM-assisted lattices exhibit a low-stress variability throughout the plateau region, yielding an overall smooth post-elastic stress-strain response, a difference that is particularly prominent for the solid-network type lattice architectures.
... High-pressure die-casting is a sophisticated process used for the mass production of aluminum castings because it is suitable to produce arbitrary complicated shapes with a high production rate. High-pressure vacuum die-casting (HPVDC) was reported to reduce significantly the porosity in the cast parts, which is caused by the entrapment of air in the molten metal during the casting process [1]. Therefore, HPVDC technique can be adopted to manufacture thinwalled parts with complicated geometry. ...
This work studied the precipitation characteristics of AlSi10Mg0.3Mn alloy produced by high-pressure vacuum die-casting in T5 and T6 conditions using transmission electron microscopy, differential scanning calorimetry and both electrical conductivity and microhardness measurements. Two different T6 tempers were used, involving partial solutionizing at 460 °C for 1 h and full solutionizing at 500 °C for 1 h, and were designated as T6P and T6F, respectively. The aging treatment was conducted at 185 °C for 4 h in all temper conditions. The results showed that conducting solution treatments resulted in the formation of α-Al(MnFe)Si dispersoids. In addition, Mg–Si rich precipitates formed and remained undissolved after partial solutionizing. The highest supersaturation of the α-Al was achieved in the as-fabricated (F) condition by the HPVDC process. The supersaturation degree decreased in both partial and full solutionizing conditions. TEM observations revealed different precipitation characteristics for T5, T6P and T6F tempers. β” precipitates just started to form in the T5 condition, whereas both β” and β’ precipitates completed their precipitation to different extents in the T6P and T6F conditions, resulting in different strengthening effects. The T6F temper yielded the highest microhardness followed by the T5 and T6P tempers.
... X-ray diffraction (XRD; Bruker AXS, D8 ADVANCE, Ulsan, Korea) was also employed to analyze the phase composition of the specimens. Finally, tensile testing (Instron, 5989, Ulsan, Korea) was performed in accordance with ASTM E08 standard to analyze the mechanical properties of the specimens before and after heat treatment [16][17][18][19][20]. The result value of each condition was measured 20 times and averaged. ...
With the rise in the demand for eco-friendly and electric vehicles, welding and heat treatment are becoming very important to meet the necessary weight reduction, complexity, and high functionality of die castings. Pore-free (PF) die casting is an effective process that enables heat treatment and welding due to low gas porosities. Indeed, this process affords castings of low gas porosity, similar to those attained by high-vacuum die casting. In this study, we compared the gas porosities of different castings fabricated by PF die casting using varied injected oxygen amounts. The castings were all subjected to T6 heat treatment and analyzed by computed tomography (CT) to compare their microstructure and mechanical properties before and after T6 heat treatment. The results revealed that with the increasing injected oxygen amount, the gas porosity of the specimens decreased while their mechanical properties increased. In particular, the gas porosity was the lowest at 1.26 L. Moreover, the 1.26 L specimen displayed the best tensile strength, yield strength, and elongation results. Finally, Weibull distribution analysis revealed that the tensile strength and elongation repeatability and reproducibility increased with increasing injected oxygen amount.
... The maximum interface thickness of around 30 µm is reported for Al-steel bimetallic, which is ~28.57% less than what has been achieved with the pressure-assisted approach herein. Bouayad et al. [26] reported air voids and porosity within the interfaces of their aluminum-steel bimetallic composite produced through the HPDC process at high pressures. They attributed it to quick cooling and low-temperature condition of the process, which would contribute to difficulty in achieving appropriate diffusion. ...
A review of the available literature indicates that the development of metal-reinforced castings present intriguing prospects but carry inherent challenges owing to differences in thermal coefficients, chemical affinities, diffusion issues and the varying nature of intermetallic compounds. It is supported that pressure application during solidification may favorably influence the dynamics of the aforementioned issues; nevertheless, not only certain limitations have been cited, but also some pressure and process regimes have not yet been investigated and optimized. This work employs the pressure-assisted approach for bimetallic steel-reinforced aluminum composite castings at a low-pressure regime and thoroughly investigates the role of three process parameters, namely pouring temperature (800–900 °C), pressure (10–20 bars) and holding time (10–20 s), for producing sound interfaces. The Taguchi L9 orthogonal array has been employed as the Design of the Experiment, while dominant factors have been determined via analysis of variance and the grey relational analysis multi-objective optimization technique. Supplementary analysis through optical micrographs, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) has been utilized to quantify interfacial layer thicknesses and to study microstructural and compositional aspects of the interface. Nano-indentation tests under static and dynamic loading have also been performed for mechanical strength characterization. It has been found that uniform interfaces with verifiable diffusion are obtainable, with the pouring temperature being the most influential parameter (percentage contribution 92.84%) in this pressure regime. The experiments performed at optimum conditions of pouring temperature, applied pressure and holding time produced a ~328% thicker interface layer, 19.42% better nano-hardness and a 19.10% improved cooling rate as compared to the minimum input values of the said parameters.
... Whereas the energy required for the production of secondary alloys is less than 5% of what needed for primary production (0.5-0.75 kWh/kg), resulting in a cheaper and more environmentally-friendly process. 1 High-Pressure Die Casting (HPDC) has been applied to produce extremely thin-walled components that can be used for parts for the automotive industry. 2 This process can be assisted by a vacuum to reduce casting defects, specifically porosity. 3 Conventional HPDC alloys are typically secondary aluminum alloys in which iron is intentionally maintained within the range of 0.8-1.1 wt.% to prevent soldering of molten metal to the die. ...
A predictive analysis was performed to investigate the effect of droplet size, section size and type of the primary and secondary AlSi10MnMg alloys on water wettability and corrosion resistance of the cast samples. An Artificial Neural Network was developed to predict the contact angle (CA) values as a function of the predictor variables. The developed model predicted unseen CA values with the correlation coefficient of 0.96 between the predicted and observed CA. The results show that the type of alloy is the most significant factor affecting CA. Confocal microscopy images demonstrate that this is attributed to the change in the heterogeneity of the surface. The corrosion studies reveal that corrosion resistance is dependent on the type of alloy and surface roughness. These results indicate that the data-driven approach is very promising not only to predict the performance, but also to design high-performance corrosion resistant surfaces of cast aluminum alloys.
... Mn content produces an elongation more than 8%. Table 2 summarizes the tensile properties of several common automotive Al alloys in the as-cast condition [3,[56][57][58][59][60][61]. It is seen that the present as-cast Sila-font®-36 alloy lies at the high end of as-cast Al alloys with a superior combination of YS, UTS and %EL. ...
Aluminum alloy is today considered as a prime selection for manufacturing lightweight structural components in the automotive industry to increase fuel efficiency and reduce harmful emissions. The aim of this study was to identify the effect of microstructure and strain rate on the tensile deformation behavior of a high-pressure die-cast Silafont®-36 alloy, with special attention to strain hardening behavior and deformation mechanisms. The alloy consisted of randomly oriented primary α-Al phase and Al-Si eutectic structure in a form of heterogeneous microstructures, with Sr-modified Si particles exhibiting a coral-like fibrous network. The local misorientations in most primary α-Al grains was below 1°, suggesting strain-free grains along with some extent of near-boundary residual strains due to the thermal mismatch between aluminum and silicon. A superior strength-ductility combination was achieved, along with enhanced Young’s modulus and quality index owing to the unique heterogeneous microstructures. The cast alloy exhibited a smooth deformation characteristic with good coordination deformation and strong strain hardening capacity. Strain hardening exponents evaluated via the equations proposed by Ludwik, Hollomon, Swift, and Afrin et al., respectively, showed basically the absence of strain-rate effect from 1×10⁻⁵ to 1×10⁻² s⁻¹. During the tensile deformation, crack initiated from the sample surface and propagated through the alternate microconstituents of softer primary α-Al phase and harder eutectic structure.
... For example, die castings have relatively poor mechanical performance due to porosity and other casting defects and the formation of a large solid lump in the shot sleeve before die filling. Major effort has been made over many years to overcome these challenges, using semisolid metal (SSM) processing [1,2], vacuum die casting [3,4] and squeeze casting [5,6]. ...
Melt quenched high pressure die casting (MQ-HPDC) is a new die casting process developed recently for improving the casting quality of the conventional HPDC process. In the MQ-HPDC process, an alloy melt with a specified dose and superheat is quenched by directly pouring the alloy melt into a preheated metallic container. The thermal mass and preheating temperature of the container is selected so that the alloy melt is quenched just below the alloy liquidus and heterogeneous nucleation takes place during the melt quenching. The quenched alloy melt is then fed immediately into the shot sleeve for component casting. In this paper we present the MQ-HPDC process and the resultant microstructures and mechanical properties of a MQ-HPDC A356 alloy.
High pressure die casting (HPDC) AlSi10MnMg alloy castings are widely used in the automobile industry. Mg can optimize the mechanical properties of castings through heat treatment, while the release of thermal stress arouses the deformation of large integrated die-castings. Herein, the development of non-heat treatment Al alloys is becoming the hot topic. In addition, HPDC contains externally solidified crystals (ESCs), which are detrimental to the mechanical properties of castings. To achieve high strength and toughness of non-heat treatment die-casting Al–Si alloy, we used AlSi9Mn alloy as matrix with the introduction of Zr, Ti, Nb, and Ce. Their influences on ESCs and mechanical properties were systematically investigated through three-dimensional reconstruction and thermodynamic simulation. Our results reveal that the addition of Ti increased ESCs’ size and porosity, while the introduction of Nb refined ESCs and decreased porosity. Meanwhile, large-sized Al3(Zr,Ti) phases formed and degraded the mechanical properties. Subsequent introduction of Ce resulted in the poisoning effect and reduced mechanical properties.
This study uses friction stir processing (FSP) for thermomechanical processing of high-pressure die-casting (HPDC) to modify microstructure and improve mechanical properties. FSP is carried out on two different HPDC aluminum alloys: (a) general-purpose, high-iron, HPDC A380 alloy and (b) premium quality, low-iron HPDC Aural-5 alloy in thin wall, flat plate geometry. Subsequent mechanical testing shows ∼30 % and ∼65 % enhancement in yield strength and tensile ductility. In addition, FSP leads to ∼10 times improvement in fatigue life for A380 alloy and ∼70 % improvement in fracture toughness for Aural-5 alloy. These findings emphasize the capability of FSP to modify the microstructure of HPDC Al-alloys-based structural components so that they can demonstrate a good combination of strength, ductility, fracture toughness, and high fatigue properties for long-term durability and reliability.
This study explores the application of friction stir processing (FSP) to enhance the material properties of Sr-modified Aural-5 alloy, with a focus on improved tensile and fatigue properties. Aural-5 is a well-known vacuum-assisted high-pressure die-cast (HPDC) Al-Si7-Mg alloy used in the automotive industry to reduce vehicle weight, enhance fuel efficiency, and lower carbon emissions. This alloy modifies its material chemistry with Sr for fine fibrous networks of eutectic silicon and manganese (Mn) to reduce die soldering. It has significantly less iron (Fe) content resulting in the elimination of detrimental needle-shaped Fe-bearing β-phase intermetallic and improving ductility. The initial microstructure of as-received HPDC Aural-5 exhibits shrinkage porosity in the middle section, a dendritic microstructure with fibrous Al-Si eutectic colonies, a shear-band structure beneath the die-wall, large dendritic externally solidified crystals (ESCs), needle-shaped Mg2Si phase and significant second-phase particulates. Some of those microstructural features, such as porosity, ESCs, needle-shaped Mg2Si phase, and large second-phase particles, serve as initiation sites for cracks under mechanical loading, resulting in adverse effects on tensile properties, particularly ductility. FSP effectively transforms the microstructure into a wrought configuration with uniform particle distribution by eliminating porosity and disintegrating dendrites, eutectic colonies, ESCs, second-phase particles, and shear-band structures. FSP-driven microstructure modification enhances yield strength and tensile ductility by ∼30% and ∼35%, respectively. The fatigue life of the material in a bending mode configuration (stress ratio R = 0.1) after FSP exhibits enhancements ranging from 2.0 to 3.9 times that of the original HPDC Aural-5 alloy, depending on the applied stress level.
In recent years, Non-Heat Treatable High Pressure Die Casting Al alloys (NHT-HPDC Al alloys) have been proposed and developed for integrated die casting in the automotive industry. These alloys exhibit excellent castability and can achieve sufficient mechanical properties without the need for heat treatment. Despite their industrial significance, there is a lack of an updated and comprehensive description of such alloys. The insufficient availability of literature and the absence of a systematic design mentality have hindered their development. Therefore, this study reviews several aspects of NHT-HPDC Al alloys. Firstly, the NHT-HPDC Al alloys are divided into Al-Si, Al-Mg-Si and Al-Fe-Mg alloys, with the NHT-HPDC Al-Si alloys being the mainstream. The solidification behaviors of NHT-HPDC Al-Si-(Cu)-(Mg) alloys are discussed using phase diagram analyses. Secondly, the manipulation of critical phases is discussed, including: (i) impurity phase: Fe-rich phase (the neutralization treatment); (ii) strengthening phases: Eutectic Si phase (the modification treatment)/main alloying elements regulating phases/trace alloying elements regulating phases/ceramic particles. Thirdly, the typical three regions of NHT-HPDC Al-Si components and their formation mechanisms are identified and reviewed. Then, the influence of vacuum assistance and intensification pressure to the general quality of NHT-HPDC Al-Si components is comprehensively discussed. Finally, future challenges for NHT-HPDC Al-Si alloys are also proposed.
div class="section abstract"> Light weight and Robust manufacturing technologies are always needed for transformation drive in the Automotive industry for the next-generation vehicles with greater Power to weight ratio. Innovations and process developments in materials and manufacturing processes are key to this light weighting transformation. Aluminium material has been widely used for these light weighting opportunities. However, aluminum joining techniques, characterized by their poor quality and consistency are limiting this transformation. This technical paper represents one of such case, where the part is made up of Aluminium through conventional casting route which has affected the laser weld quality due to poor casting soundness. This experiment explains in detail about the importance of Casting soundness for laser weld quality, weld penetration, strength etc., and the Product consistency. Casting soundness improvement explored with the support of Ingot quality, Die design, Gating design & Size, Overflow designs, Air vent provisions, Vacuum system etc., through Simulation and Developments. This technical paper will support for knowledge enhancement on casting soundness and process robustness importance towards weld quality.
</div
In this work, a modified Al–Si–Mg (A356) alloyA356 alloy was prepared by vacuumVacuum-assisted high pressure die castingHigh Pressure Die Casting processes (V-HPDC). To release residual stresses, various thermal treatment schemes over a wide range of temperatures between 120 and 350 °C were experimented to the as-cast V-HPDC alloy, in an effort of understanding the effect of thermal treatment on tensile properties of V-HPDC modified Al–Si–Mg (A356) alloyA356 alloy. The morphology of eutecticEutectic silicon has a sound effect on the tensile properties of the tested alloy. The content of magnesium-based intermetallic phase, their morphology, and distribution throughout the matrix affect the tensile properties as well. The reductionReduction in the strengths of the alloy treated at 350 °C for two hours should be at least attributed partly to the absence of the magnesium-based intermetallic phase. However, the presence of sufficient amount of magnesium intermetallic phase plays an important role in strengtheningStrengthening the alloy thermally treated at 200 °C.
While rare-earth Mg alloysMagnesium alloy have remarkable properties for high strength applications, lower cost alternatives are necessary for the widespread industry use of Mg. Ca added Mg alloysMagnesium alloy have shown promise as an alternative to rare-earth alloys. Ca-based precipitates can reduce basal texture, reduce casting porosity, and increase mechanical strength of cast components. However, the accumulation of Ca-based precipitates along inter-dendritic regions can severely limit ductility. Here, we apply two solid-phase processing techniques, friction stir processingFriction stir processing and shear assisted processing and extrusionShear assisted processing and extrusion, to produce wrought microstructure sheet and extruded tubes from a cast Mg–Al–Mn–Ca alloy. Ductility of the alloy is enhanced by densification under the applied thermomechanical processingThermomechanical processing conditions, grain refinement, and refinement of (Al, Mg)–Ca-based precipitates. Solid-phase processing provides a low cost opportunity to improve the properties of cast Mg alloysMagnesium alloy and improve service life.
Alternate fuels and powertrain systems will force an increased premium on vehicle mass reduction both to make vehicles more fuel efficient and to enable greater range. An analysis shows that life cycle analysis can be used to quantitatively assess how the use of alternate materials to reduce mass will contribute to energy savings and carbon footprint reduction. This justifies aggressive mass reduction driven by the use of alternative materials. Also, a detailed look at auto construction shows that the vehicle of the future will likely be made of many materials. This poses many new challenges in design, manufacturing, joining and durability.
The effects of Cr and Ti on the thermal conductivity and mechanical properties of Al–7Si–3Mg die-casting alloys were investigated in the present study. For alloy design, solidification behavior and thermal conductivity of all phases were examined by thermodynamic calculations. The results showed that the alloys with intermetallic compounds exhibited good mechanical properties, but thermal conductivity was relatively low. As a result of predicting solidification behavior and physical properties of each phase through computational thermodynamic simulations, the effects of the addition of Cr and Ti on the change in the fraction of the precipitated phase in Al–Si–Mg–Fe alloys were examined. Yield strength and ultimate tensile strength were found to be the highest in the case of the Al–7.2Si alloy with the addition of 4.39 wt%Mg and 0.45 wt%Cr (S-5 alloy). The mechanical properties of other alloys (S-1 to S-4) showed almost similar values. Thermal conductivity was found to be similar in the case of S-1 to S-3 alloys. The thermal conductivity was found to be directly proportional to the fraction of α-Al phase and the lowest in the case of S-4 alloy due to the presence of low fraction of the α-Al phase. The S-5 alloy was found to have the best mechanical properties as well as optimal thermal conductivity. To improve the mechanical property and thermal conductivity simultaneously, it is important to control the fraction of the second phase of the alloy. In contrast with Cr which formed intermetallic compounds with major alloying elements, Ti did not produce intermetallic compounds at a small addition. However, Ti affected the solidification behavior of other phases which changed the properties of the alloys. It was found that not only the type of alloying element but also the amount of addition are important for the improvement of thermal conductivity and mechanical properties of Al–Si–Mg alloys.
Preface
The present book volume, Metal Matrix Composites: Fabrication, Production, and 3D Printing will provide great support and basic knowledge of MMCs to readers undergoing different programs related to Mechanical and Materials Technology, irrespective of the stream they opt for. All the engineers and designers are directly or indirectly involved in the manufacturing of metal matrix composites and its related processes. In general, Composites are made of two or more materials with a combination of required properties and are used by both manufacturers and industrialists. Moreover, understanding their manufacturing processes is paramount as these processes vary as do the materials. Hence, engineers and researchers opting for this profession should have deep knowledge about the materials and preparation of MMCs. The users can provide the best feedback and if they happen to be engineers, their feedback may help in better design, cost reduction, alternative material, and the process of making a part or machine or structure. The present book intends to provide in-depth knowledge for easy understanding of concepts. This book brings in the elements of the manufacturing of metal matrix composites with a detailed focus on its fabrication, production, and 3D printing. Real-life examples have also been used in the text rather than just describing the process. Also, the different authors have tried to explain the concepts and reasons in the best possible way.
The combination of light metals (aluminum, magnesium and titanium) and innovative casting processes provides cost-effective technologies to produce lightweight components and systems for many industrial applications. This article provides a comprehensive and yet critical review of light alloy development for cast components used in lightweight and high-performance structural and propulsion applications. It also summarized some latest process innovations in gravity casting, high pressure die casting, and low pressure casting, to overcome some fundamental issues related to defect formation in casting processes. Emerging casting processes developed in the last twenty years, such as semisolid processing, squeeze casting, ablation casting, bimetallic overcasting, and diffusion solidification processing, are discussed for further development. Recent advances in casting simulation and the concept of Integrated Computational Materials Engineering (ICME) are summarized for casting applications. Finally, future perspectives in light alloy development (including green alloys, high entropy alloys and metal matric composites), process innovations (such as high integrity casting, multi-material manufacturing and additive manufacturing), and ICME development are presented to stimulate further research and sustainable development in this important field of metals processing technology.
This work employs friction stir processing (FSP), a well-known severe plastic deformation technique, to selectively modify the microstructure of thin-walled, high-pressure die-cast (HPDC) aluminum alloy A380, a major HPDC alloy fabricated in the die casting sector. FSP effectively breaks down Al dendrites and acicular Si particles, creating a homogenized distribution of equiaxed Si particles in the aluminum matrix. After FSP, the refined Si particles (~1.5 μm) are smaller than the eutectic Si particles (3–8 μm) in HPDC condition. In addition, interparticle distance has decreased almost 50% compared to dendritic arm spacing, and FSP has reduced the aspect ratio of Si particles to ~2. Furthermore, FSP eliminates porosity, and breaks down needle-like second-phase Fe-Mn and Cu-rich particles, yielding a refined, homogeneous distribution. The FSP-induced microstructural refinement and porosity reduction improve bulk yield strength and ductility by 23% and 66%. Tensile properties are enhanced beyond those of the die skin of the HPDC plate, and the alloy possesses lower defect density and a highly refined microstructure. This study establishes the viability of FSP as a tool for microstructure modification and mechanical property improvement for HPDC Al alloys for the light-weighting goal of the automotive industries.
As one of the most important forming technologies for industrial bulk metallic glass (BMG) parts with complex shapes, high-pressure die casting (HPDC) can fill a die cavity with a glass-forming metallic liquid in milliseconds. However, to our knowledge, the correlation between flow and crystallization behavior in the HPDC process has never been established. In this study, we report on the solidification behavior of Zr55Cu30Ni5Al10 glass forming liquid under various flow rates. Surprisingly, the resulting alloys display a decreasing content of amorphous phase with increase of flow rate, i.e. increase of cooling rate, suggesting that crystallization kinetics of glass-forming metallic liquids in the HPDC process is strongly dependent on the flow field. Analysis reveals that the accelerated crystallization behavior is mainly ascribed to the rapid increase in viscosity with a decreasing temperature as well as to the huge shear effect in the glass-forming liquid at the end stage of the filling process when the temperature is close to the glass-transition point; this results in a transition from diffusion- to advection-dominated transport. The current investigation suggests that flow-related crystallization must be considered to assess the intrinsic glass-forming ability of BMGs produced via HPDC. The obtained results will not only improve the understanding of crystallization dynamics but also promote the high-quality production and large-scale application of BMG parts.
In the present study, effect of secondary phase on mechanical property and thermal conductivity of newly developed high-pressure die-cast Al-6Si-0.3Fe-1.5Mg(S-1), Al-6.5Si-0.4Fe-1.6Mg-0.7Cu-0.08Mn(S-2), and Al-8Si-0.5Fe-0.5Mg-1.5Cu-0.10Mn-0.1Ni(S-3) alloys were investigated. The fraction of α-Al phase and secondary phase has been predicted by thermodynamic simulations. UTS was found to be 307MPa, 331MPa and 350MPa for S-1∼3 alloys. The thermal conductivities values are 160.3W/mK, 153.0W/mK, and 146.0W/mK for S-1∼3 alloys. The S-3 alloy has the highest fraction of the secondary phases and as a result of the addition of Fe and Cu is partially precipitated into the Al5Cu2Mg8Si6, Al7Cu2M and β-AlFeSi phases. The mechanical properties of these alloys were found to be directly proportional to the fraction of Si addition as well as secondary phases, whereas thermal conductivity shows the opposite trend. Newly developed S-3 alloys in the present study showed excellent mechanical and thermal conductivity as compared to other Al alloys reported in the literature.
The manufacturing of extra-large thin-wall castings using high pressure die casting is one of the most significant challenges for structural applications requiring excellent ductility. The present study aims to understand the effect of process parameters on the castability, defect formation and mechanical properties of aluminium alloys in extra-large thin-wall castings with a maximum flow length of 1230 mm in the 2.8 mm thick channel. Numerical simulation and experimental verification were carried out to tailor the process parameters in high pressure die casting. It is found that the process parameters can significantly affect the castability and mechanical properties of as-cast components. For a complete casting, the yield strength is slightly increased but the elongation is significantly decreased at the locations further away from runners. A new concept of effective flow length (EFL) is proposed and used to assess the castability in extra-large thin-wall high pressure die castings. Under the optimum casting condition, the EFL can reach 525 mm, at which the ratio of EFL to wall thickness is 187 and the yield strength and elongation are greater than 120 MPa and 10%, respectively. Although the extra-large thin-wall castings can be geometrically filled under several conditions, the heterogeneity of mechanical properties is the most significant concern, in which the variation of elongation is overwhelmingly important for the structural applications requiring excellent ductility under as-cast conditions. Therefore, the criteria of casting quality should consider both geometrical soundness and the homogeneity of mechanical properties in the casting body.
The lightweight die-casting Al-alloys have become a more appropriate material in many industrial applications. However, the product’s quality has been affected due to existing internal casting defects and the impregnation technique used to overcome drawbacks and improve alloys’ useability. This paper discusses the use of microfocus X-ray computed tomography (XCT) to examine Al-alloy’s die-casting internal deformity, identify the impregnation technique’s effectiveness in sealing porosity non-destructively. Also, we recognize the presence of low atomic number polymer resin (P601) inside the alloy’s defects quantitatively. 3D CT images with transparent effects were generated with a direct conversion X-ray flat panel detector to visualize internal casting defects in the entire samples. The gray-value contrast of 2D slice CT images was excellent to distinguish the resin material in the alloy samples qualitatively. The dimensional analysis shows that the impregnated resin does not seal the casting cavity homogeneously, and some air bubbles appeared inside the defects. The dual-energy X-ray CT technique with a photon-counting detector was executed to characterize the impregnant resin in die-casting cavities by its effective atomic numbers. The outcome shows that the resin material present in alloy’s defects is identical to the solid P601 super-sealant impregnant resin, with a 1.81% error margin. Hence, the XCT technique with a direct-conversion CdTe detector can be used as a rapid and detailed non-destructive inspection technique in die-casting industries and improve the impregnation process’s performance.
Significant progress has been made for assessing the influence of porosity on the performance metrics for cast components through various modeling techniques. However, a computationally efficient framework to account for porosity with various shapes and sizes is still lacking. The main contribution of this work is to address this limitation. Specifically, a novel porosity sensitivity method is proposed, which integrates the merits of topological sensitivity and shape sensitivity. While topological sensitivity approximates the first order change on the quantity of interest when an infinitesimally small spherical pore is inserted into a dense (no pore) structure, shape sensitivity estimates the subsequent change in the quantity when the small pore’s boundary is continuously perturbed to resemble the geometry reconstructed from tomography characterization data. In this method, an exterior problem is solved to explicitly formulate pore stress and strain fields as functions of shape scaling parameters. By neglecting higher order pore-to-pore interaction terms, the influence of multiple pores can be estimated through a linear approximation. The proposed method is first studied on a benchmark example to establish the impact of different pore parameters on the estimation accuracy. The method is then applied onto case studies where the pore geometry is either from tomography reconstruction or computer-generated representations. Efficiency and accuracy of the method are finally demonstrated using a commercial 3D application. The proposed method can be extended to other manufacturing (e.g., additive manufacturing) induced porosity problems.
Herein, a systematic study was carried out to investigate the effect of wall thickness (2, 4, 6, 8 mm) and intensification pressure (65, 80, 95 MPa) on the microstructures and mechanical properties of AlSi7-SiC composites fabricated by the vacuum-assisted the high-pressure die casting process. The results revealed that the pore's number initially decreased with the increase of wall thickness, followed by a gradual increase, and the pore's type changed from gas pore to shrinkage pore and concentrated in the central region of the sample. When the intensification pressure increased, the distribution of SiC particles and eutectic Si became more uniform, and the porosities of samples with different wall thicknesses decreased significantly. Furthermore, the change in tensile strength remained consistent with the porosity's variation, while samples' elongation increased with the increase of wall thickness. The sample with a wall thickness of 4 mm under an intensification pressure of 95 MPa obtained the maximum tensile strength of 298 MPa, increased by 52.8% compared with AlSi7-SiC composites fabricated by squeeze casting.
Porosity formation in high pressure die casting (HPDC) impacts mechanical properties and casting quality. Much is published regarding micro porosity and its impact on mechanical properties, but there is limited research on the actual formation of macro porosity. In production applications, macro porosity plays a critically important role in casting quality and acceptance by the customer. This paper argues that the most useful definition of macro porosity is the limits of visual detectability. With this definition, it will be shown macro porosity presents stochastically within a controlled HPDC process. This means macro porosity has a random probability distribution or pattern that should be analyzed statistically and cannot be predicted precisely. The general region where macro porosity forms is predictable with simulation, but its actual size and distribution of the voids are random. These results challenge the industry accepted practices for inspections and process controls. This also underscores the importance of up-front design for manufacturability to avoid macro porosity-related quality issues.
The morphological properties and distribution characteristics of primary iron-rich phase in a high-pressure die-cast hypoeutectic Al-Si alloy were investigated by synchrotron X-ray tomography technology. Attention was focused on the formation and evolution mechanism of primary iron-rich intermetallic compounds (IMCs) in high pressure die casting (HPDC). Results show that two different sizes of primary iron-rich phases included externally solidified primary iron-rich phase I ((P-IMC)I) and primary iron-rich phase II ((P-IMC)II). The morphology of (P-IMC)I was close to a hexahedron while (P-IMC)II was nearly a spherical particle. Both (P-IMC)I and (P-IMC)II enriched in the central area and their volume fraction maintained a high level from defect band to center. Phase calculation show that (P-IMC)I (601°C) preferentially precipitated from liquid and its further growth led to the decrease of Mn/Fe ratio in the subsequent formed (P-IMC)II. In HPDC solidification process, (P-IMC)II exhibited a lateral growth pattern with the terminating surfaces determined to be {1 1 0} planes. In addition, the hexahedral (P-IMC)I in central ESCs-rich zone developed into a dendrite along its corner <100> direction.
In this study, the effects of pressure (vacuum) on solidification characteristics of specimens produced by isolated sand mould, conventional gravity casting and counter gravity casting were investigated. In this work, the effects of counter gravity casting process parameters on grain size, cooling rate and other thermal characteristic results of Al-Si cast alloy have been described. The solidification process was studied using the cooling curve under 0, 0.133 and 0.666 bar vacuum levels. The experimental alloy used in this investigation was Al-Si 9.42 % commercial alloys. Cooling curve and thermal analysis were performed on all samples using high sensitivity thermocouples of K type. Increasing the cooling rate decreases significantly the nucleation temperature, solidification range and time. Therefore, increasing cooling rate refines all micro and macrostructure features. The results showed that decreased solidification time (80), smaller grain size (79) on the solidified castings were obtained by counter gravity casting process.
Free flowing of liquid metal through the gate during die filling and solidification is critical to the final product quality in aluminium high pressure die casting. Early close-off of the gate due to freezing detrimentally affects the pressure transmission from the injection system to the casting as it solidifies, resulting in poor soundness of castings due to improper feeding of the shrinkage.
In this paper, piezoelectric cavity pressure sensors were employed to study the gate freezing behaviour in aluminium high pressure die casting. Metal pressure at the runner, gate and cavity was directly measured during casting. From the on-line measured metal pressure profile, a method was established for analysing the gate freezing time. The effect of process variables on the gate freezing time, such as intensification pressure and gate speed, as well as their relation to the mechanical properties of the produced castings, was studied in detail. It was found that the gate freezing time could be determined by the duration from the start of the cavity fill to the drop in pressure measured at a location just after the gate. The application of higher gate velocity and pressure assisted in keeping the gate open longer. As a result, sound castings were produced and mechanical properties were improved. The results indicate that the method developed in this work can be used to control and optimise the die casting process for the fabrication of high internal integrity components.
Present address: Tesma International Inc., 40 Citron Court
- Corresponding
* Corresponding author. Present address: Tesma International Inc., 40 Citron Court, Concord, Ont., Canada L4K 2P5. Tel.: 1-905-738-1200; fax: 1-905-669-3612.
The Die Casting Books
- A Street
A. Street, The Die Casting Books, Portcullis Press Ltd., 1977, pp. 3± 16, pp. 625±641.
Die Casting Metallurgy
- A Kaye
- A Street
A. Kaye, A. Street, Die Casting Metallurgy, Butterworths, London, 1982, pp. 231±235.
Producing heat treatable Al die castings: Part II, Die Casting Management
- H Woithe
- W Achwab
H. Woithe, W. Achwab, Producing heat treatable Al die castings: Part II, Die Casting Management (October 1993) 29±31.
Re-engineered casting combines, metal flow, vacuum technologies, Modern Metals
- J N Pennington
J.N. Pennington, Re-engineered casting combines, metal ¯ow, vacuum technologies, Modern Metals (July 1996) 48B±48G.
Vacuum high technology for top quality pressure die castings
- K Baumgartner
K. Baumgartner, Vacuum high technology for top quality pressure die castings, in: Proceedings of the 15th International Pressure Die Casting Conference, Montreaux, Switzerland, May 22, 1996.
Evaluating the quality of vacuum die castings, Transactions of North American Die Casting Association
- J R Brevick
- P S Cheng
J.R. Brevick, P.S. Cheng, Evaluating the quality of vacuum die castings, Transactions of North American Die Casting Association, 1995, pp. 145±148.