Pressure Die Cast Research Articles

Microstructure and properties of AlSi12Fe alloy high pressure die-castings under different vacuum levels

AlSi12Fe alloy die castings were produced by vacuum-assisted high pressure die casting (HPDC) process under different vacuum levels: 275 mbar, 112 mbar, and 72 mbar. The porosity, mechanical properties and thermal conductivity of the castings were investigated. The results show that increasing vacuum level can significantly reduce the average porosity and improve yield strength. The Weibull analysis confirmed that vacuum-assisted HPDC improved the repeatability of the tensile properties. Meanwhile, the thermal conductivity increased with the vacuum level. When the porosity reduced from 0.152% to 0.046%, the thermal conductivity increased from 128.52 W/(m·K) to 133.45 W/(m·K).

Microstructures refinement and mechanical properties enhancement of aluminum and magnesium alloys by combining distributary-confluence channel process for semisolid slurry preparation with high pressure die-casting

Abstract A simple and efficient semisolid slurry preparation technique, called distributary-confluence channel (DCC), was developed to prepare high-quality semisolid slurries of aluminum and magnesium alloys. The DCC process was coupled with the use of a high pressure die-casting (HPDC) machine to successfully achieve near-net forming and implement production applications with rheological high pressure die-casting (Rheo-HPDC) for various Al and Mg alloy castings. The changes in the flow state and in the physical field of the melt during the slurry preparation via the DCC technique were investigated by numerical simulations. The nucleation mechanism and the growth law of the primary grain during the DCC process were discussed. The microstructures, porosities, and mechanical properties of the aluminum and magnesium alloys prepared via DCC Rheo-HPDC were studied. The results show that semisolid slurries containing a large amount of primary grains with an average size 0.8, and uniformly dispersed in the liquid matrix can be prepared via DCC. The simulation results indicate that the melt exhibits opposite velocity vectors on the upper part and on the lower part of the DCC. Moreover, it encounters and collides at the confluence to generate convection, which is beneficial to obtain uniform melt temperature, composition fields, nuclei exfoliation, and spherical growth. The random particle tracking simulation results show that the DCC process improves the composition field of the slurry. The DCC process facilitates the melt nucleation by using multi-channel chilling and increasing the nucleation area. The self-stirring generated during the flow of the melt produces a large amount of free nuclei inside the melt. There exist two main mechanisms behind the formation of the spherical primary grains. The one is the mechanism of explosive nucleation and spheroidal growth, the other is the dendrite arm necking, fusing, grain ripening, and rounding. Furthermore, by comparing identical alloy castings produced via traditional HPDC and other Rheo-HPDC processes, the DCC Rheo-HPDC castings present finer and rounder grains, a lower porosity, and more performant mechanical properties.

Effect of Material Segregations Due to Squeeze Parameters on Mechanical Properties of High Pressure Diecast Parts

Abstract This article is a research on the effect of material segregations due to squeeze parameters on mechanical properties of high pressure die cast parts. The technology of squeezing is applied in high pressure die casting technology with the aim to improve the internal material health of the castings from aluminium alloys, such as AlSi9Cu3(Fe), components incorporated in assemblies as mechanical and hydraulic parts. The objective of this article is to determinate the influence of the secondary effects of squeeze technology on the mechanical properties of parts produced from AlSi9Cu3(Fe) alloys, with HPDC technology.

Linear Elastic FE-Analysis of Porous, Laser Welded, Heat Treatable, Aluminium High Pressure Die Castings Based on X-Ray Computed Tomography Data.

The welding of aluminium high pressure die castings is a well known and broadly investigated challenge in various fields of industry and research. Prior research in this specific field mainly focused on the optimisation of the welding and the casting process and on the cause of the frequently occurring porosity and incomplete fusion phenomena, whereas the impacts of these defects have hardly been addressed. Therefore, the underlying study presents the investigation of weldments in EN AC-AlSi10MnMg high pressure aluminium die castings by linear elastic finite element analysis based on X-ray computed tomography as a novel approach. Hereby, four laser weldments with differing surfaces and pore contents were investigated by X-ray computed tomography and tensile testing. Based on the voxel datasets of the porous weldments, triangular finite element meshes were generated and a numerical finite element analysis was conducted. Good agreement of the stress–strain curves between the simulations and the experiments was achieved.

A novel rheological high pressure die-casting process for preparing large thin-walled Al–Si–Fe–Mg–Sr alloy with high heat conductivity, high plasticity and medium strength

An air-cooled stirring rod (ACSR) process for efficiently preparing large volumes of semisolid slurry was introduced. A new low-cost casting Al–Si–Fe–Mg–Sr alloy was used to prepare large thin-walled heat-dissipating shells using both conventional HPDC and ACSR rheological high pressure die-casting (Rheo-HPDC) technologies. Their microstructures, thermal conductivities, elevated temperature and room temperature mechanical properties, and corrosion behaviors were compared. Furthermore, this work analyzed the mechanisms responsible for the microstructure refinement and performance enhancement in ACSR Rheo-HPDC alloys. The results showed that only 25 s was needed to prepare 32 kg of the semisolid slurry using ACSR process. The alloy prepared by ACSR Rheo-HPDC generated a large number of fine spherical primary α-Al particles with a volume fraction greater than 40%. The Rheo-HPDC alloy showed a moderate strength, high plasticity, and high heat conductivity. The heat conductivity, ultimate tensile strength and elongation of the Rheo-HPDC alloy were 184 W/(m.K), 264 MPa and 12.2% respectively, while those of the HPDC alloy were 167 W/(m.K), 228 MPa and 5.8% respectively. The improvement of heat conductivity of the alloy formed via ACSR Rheo-HPDC was mainly ascribed to the decrease of electron scattering by the refinement of eutectic silicons and Fe-rich intermetallics. This allowed the electron flow to pass through the eutectic Si region more easily. The refined and uniformly-distributed heat-resistant β-Al5FeSi intermetallics effectively prevented grain boundary sliding, so the Rheo-HPDC alloy showed superior high-temperature mechanical properties. The Rheo-HPDC alloy presented a more excellent corrosion resistance to the conventional HPDC alloy due to the refinement of iron-rich phase and eutectic silicons and the reduction in the potential difference between the matrix and the iron-rich phase.

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.

Addition of Swarf to Produce a Semi-Solid Slurry during High Pressure Die-Casting of AS9U3 Aluminum Alloy

An internal cooling agent is used in rapid slurry forming (RSF) process to produce a high solid fraction slurry for a short period of time. In the process used in this research, the swarf which is known to be a low enthalpy material was added to the melt as the internal cooling agent. During the process, the swarf started to melt and a semi-solid slurry with a relatively high solid fraction was formed. This slurry was formed by exchanging the enthalpies between the low and high enthalpy materials. A commercial Al-Si-Cu alloy, i.e. AS9U3 Aluminum alloy, was used in this investigation. The microscopic examination showed that the Al-Si eutectic colonies start to melt during the melting process of swarf material resulting in the formation of globular Alpha-Al grains due to the multiplication of secondary dendrites arms. The fracture of dendrites arms and the subsequent spheroidization were suggested to be the origin of non-dendritic globular grains in the final microstructure. The amount of primary globular Alpha-phase was measured by the image analysis software. The results showed that during high pressure die-casting of AS9U3 Aluminum alloy using 4 mm thick samples, around 35 percent solid has been formed at the temperature of 580 oC.

Industrialized Application of Rheo-HPDC Process for the Production of Large Thin-Walled Aluminum Alloy Parts

A simplified and efficient process, namely air-cooled stirring rod (ACSR), was proposed to prepare semisolid slurry of aluminum alloys. An advanced integrated rheological high pressure die-casting (Rheo-HPDC) technology was established by combining the ACSR equipment with HPDC machines to produce high quality aluminum alloy products. Microstructures, surface qualities, mechanical properties, corrosion resistances and thermal conductivities of the Al-8Si alloy parts prepared by Rheo-HPDC were investigated and compared to those prepared by traditional HPDC. The results indicated that the Rheo-HPDC process can prepare aluminum alloy parts in which the primary particles are fine and spherical, and there is few shrinkage porosity. Multifarious high quality large thin-walled aluminum alloy parts, such as filter shells, cooling shells, antenna crates and mounting brackets for communication, were produced by the process. Rheo-HPDC alloys showed improved surface quality to those formed by traditional HPDC, and the surface roughness is small and avoid employing CNC to surface finish. Also, compared with HPDC alloys, the alloys prepared by Rheo-HPDC have an increased mechanical properties and thermal conductivity due to high density and refined microstructure. Furthermore, Rheo-HPDC aluminum alloys indicated a remarkable improvement in corrosion resistance as shown by the results of electrochemical and weight loss experiments.

Effect of processing routes on structure-property correlationship of ADC 12 Al alloy

The present work focuses primarily on the effect of processing routes on structure-property correlationship of ADC 12 Al alloy. Both conventional processing (Gravity cast and pressure die cast) and Semi Solid processing techniques (cooling slope and Rheo-Pressure Die Cast; RPDC) were attempted to bring out the correlationship between their microstructures and mechanical properties of ADC 12 Al alloy. Gravity cast experiment was done on ingots of ADC12 Al melted in an resistance furnace and poured at temperature 585 °C in a copper mould. In the Pressure Die-Casting process, ingots of ADC12 Al alloy were melted in an resistance furnace and the liquid metal was poured in the mould of the pressure die casting system. Semi-solid metal processing was carried out using cooling slope experiments in a developed in-house set up and effect of rheocasting on the semi solid microstructure was studied. Rheo pressure die cast experiments were carried out in an integrated set-up of cooling slope and pressure die-cast system. The obtained result of gravity cast material reveals dendritic morphology of primary Al phase and elongated eutectic phase; upon using pressure in a pressure die cast system, the structure of primary Al phase changes to large size dendrites along with rosette shaped morphology. The cooling slope technique to generate semi-solid structure yields nearly globular and fine grains; whereas the rheo pressure die casting experiments reveal nearly globular shape primary Al exhibit that distribute relatively uniformly in the matrix compared to the all three above the processing routes. From The best mechanical properties are also obtained in Rheo-pressure die cast system with tensile strength (223 MPa), elongation (6.5%), and hardness (87 VH) compared to all other processing routes. Explanations of fracture micro mechanisms are supplement to the investigation.

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.

Efficient and fast monitoring and disruption management for a pressure diecast system

Abstract An increasing amount of information is collected in industrial production processes. In many cases, this data is only accessible to the vendor of the machines involved in the production process. In the government-funded research project BigPro, we propose a flexible and fast Big Data platform that allows detection and reaction to incidents and anomalies in the production process in near real-time.

Microstructures, mechanical properties, and corrosion behavior of novel high-thermal-conductivity hypoeutectic Al-Si alloys prepared by rheological high pressure die-casting and high pressure die-casting

The microstructures, mechanical properties, thermal conductivities, and corrosion behavior of novel high-thermal-conductivity hypoeutectic Al-Si alloys, prepared by rheological high-pressure die-casting (Rheo-HPDC) and HPDC, were investigated and compared. The microstructure of the Rheo-HPDC alloy, including the primary α-Al (α1), secondary α-Al (α2-Al), β-Al5FeSi, and Si phases, was significantly more refined than that of the HPDC alloy. Compared to the HPDC alloy, the Rheo-HPDC alloy exhibited superior mechanical properties and thermal conductivity, and its ultimate tensile strength (UTS), yield strength (YS), elongation, hardness, and thermal conductivity were improved by 27%, 21%, 72%, 10% and 8%, respectively. Pitting corrosion of the Rheo-HPDC alloy was observed to originate at the interfaces between the Fe-rich intermetallics and the α2-Al particles. Corrosion was observed to propagate in the eutectic areas upon prolonged immersion in 3.5 wt% NaCl solution. Electrochemical testing, scanning Kelvin probe (SKP) measurements, and corrosion-morphology analyses reveal that the Rheo-HPDC alloy has better corrosion resistance, primarily due to the decrease in the potential difference between the Fe-rich intermetallics and the matrix, the refinement of the eutectic Si and intermetallics, and the decrease in the areal ratio of eutectic Si to α2-Al.

Mechanical characterization of integral aluminum-FRP-structures produced by high pressure die-casting

Due to the growing demand for light-weight solutions in a wide range of industrial sectors, the selection and combination of different materials is becoming more and more important. As a result, there is an increasing need for suitable joining technologies. In a new joining process, flexible glass fiber textiles are integrated into aluminum by high pressure die casting in the first production step. These structures are used for the electrochemical insulation between aluminum and carbon fiber textiles, which are connected in the subsequent production step by textile technology. The finished compound is formed in a final resin impregnation process. Challenges faced by Fraunhofer IFAM lie in the positioning, pre-tensioning, and infiltration of the glass fiber textiles in the high pressure die-casting process. The advantage of this joining technology, in addition to the electrochemical insulation between aluminum and carbon fibers, is in a slim and light-weight connection. Therefore, no thickening of the individual joining partners is necessary, and the force flow lines are not deflected. Within mechanical investigations of those hybrid structures it was determined, that the infiltration content of aluminum has only a small influence on the achievable tensile strength. Rather, casting parameters such as the holding pressure have an influence. The subsequent resin infusion process enables an additional infiltration by the resin system of fiber bundles that have been only slightly infiltrated with aluminum. As a result, additional adhesion can be achieved and the infiltration gaps can be closed. Furthermore, an influence on the achievable tensile strength was observed regarding the use of the fiber material. Further increases in tensile strengths were also observed by adapting the textile parameters (e.g. reduction of the fiber undulations). A variety of failure behaviors could be observed in dependence on textile and process parameters. Tensile strength of the hybrid structures was compared to reference samples made of glass fiber reinforced epoxy resin, to determine the loss of strength caused by the joining technology. Further investigations were carried out, including a fracture surface analysis using a scanning electron microscope. Thus it was possible to determine mechanisms of adhesion between encapsulated glass fibers and the surrounding aluminum matrix.

Study of selective deposition mechanism of cerium-based conversion coating on Rheo-HPDC aluminium-silicon alloys

Cerium-based conversion coatings were deposited on Rheo-High Pressure Die Cast (HPDC) Al-Si alloys by immersion in cerium nitrate aqueous solutions. Rheocast Al-Si alloys have a heterogeneous microstructure and present a challenge for the conversion treatment. Different parameters were studied to optimize the conversion coating, and NaCl or H2O2 were also added to the solution to modify or accelerate the deposition process. The mechanism of the coating formation was studied by means of focused ion beam milling (FIB) assisted SEM. The results show that applying cerium-based conversion coating to Al-Si alloys, is possible and a preferential deposition is obtained due to the presence of iron-rich intermetallic particles inside the eutectic region. The formation mechanism of selectively deposited cerium-based conversion coating includes dissolution of aluminium matrix, selective dissolution of aluminium from the noble intermetallic particles, oxidation of iron from the intermetallic particles, and the deposition of cerium hydroxide/oxide layer. The results reveal that the improvement in corrosion resistance in the presence of selectively deposited cerium-based conversion coating is more significant compared to the homogenous coating deposited from the conversion solution containing H2O2.

Sustainable Modeling of Die-Casting Processes through Matlab

Manufacturing industries are facing tough competition due to increasing raw material cost and depleting natural resources. There is great pressure on the industry to produce environmental friendly products using environmental friendly processes. A computer-aided system named Sustainability Assessor for Die-casting has been developed and presented in this work. The system can assess the sustainability performance of a die casting process plan. The system determines the CO 2 emissions, solid waste, and energy use based on the process plan information. Two case studies for gravity die-casting and pressure die-casting are demonstrated the sustainability analysis based on system developed. The proposed system is verified by comparing results with the actual data measured from the shop floor. The developed system is beneficial for sustainability assessment comparing different plans alongside material properties, ultimately helping the die-casting industry to reduce the carbon emissions and material waste, besides improving energy efficiency. It is expected that this would be highly beneficial for determination of environmental impact of a process at early design stages. Therefore it would greatly help the manufacturing industry for selection of process plan based on sustainable indices. Overall impact of this study would have good impact on reducing air emissions and protecting environment.

Corrosion Behavior of High Pressure Die Cast Al-Ni and Al-Ni-Ca Alloys in 3.5% NaCl Solution

In this investigation corrosion behavior of newly developed high-pressure die cast Al-Ni (N15) and Al-Ni-Ca (NX1503) alloys was studied in 3.5% NaCl solution. The electrochemical corrosion behavior was evaluated using open circuit potential (OCP) measurement, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. Potentiodynamic polarization results validated that NX1503 alloy exhibited lower corrosion current density (icorr) value (5.969 μA/cm2) compared to N15 (7.387 μA/cm2). EIS-Bode plots revealed a higher impedance (|Z|) value and maximum phase angle value for NX1503 than N15 alloy. Equivalent circuit curve fitting analysis revealed that surface layer (R1) and charge transfer resistance (Rct) values of NX1503 alloy was higher compared to N15 alloy. Immersion corrosion studies were also conducted for alloys using fishing line specimen arrangement to simultaneously measure corrosion rates from weight loss (PW) and hydrogen volume (PH) after 72 hours and NX1503 alloy had lower corrosion rate compared to N15 alloy. The addition of Ca to N15 alloy significantly reduced the Al3Ni intermetallic phase and further grain refinement may be attributed for reduction in the corrosion rate.

Compute-Aided Design of Low Pressure Die-Casting Process of A356 Aluminum Wheels

The lightweight design of aluminum automobile wheel can easily bring about all kinds of defects during die-casting, which often causes wheel frame deformation and creep damages in the future use and in turn affects traffic safety. To understand the evolution of mold flow, temperature field, and solidification, the low pressure die-casting processes of A356 aluminum wheel were simulated by Anycasting software package. Various casting parameters combined with the designs of flow channel and overflows were adopted to reduce the defects occurred in wheel products. In addition, we adopted the retained melt modulus (RMM) to predict the position of defects to be formed as well as their distribution so as to eliminate the shrinkage voids and porosity defects during die-casting. The research findings showed that the setting up of overflow tank could effectively prevent the formation of shrinkage void and porosity of die-castings and significantly promote the quality and productivity of die-casting wheel products.

Numerical Simulations of Low Pressure Die-Casting for A356 Aluminum Rims

This study conducted mold flow analyses on low pressure die-casting A356 aluminum rims to improve the shrinkage and porosity defects which usually occurs in die-castings so as to enhance the quality of die-casting wheels. We adopted different lift tube designs with cylindrical, taper opening and back taper opening structures while discussing the filling, exhaust, and solidification of molten flows and predicting the shrinkage and porosity formed based on the retained melt modulus. The study found that the configuration of lift tube as well as the optimization of process parameters such as the processing pressure and progressive time could effectively reduce the formations of shrinkage and porosity defects and improve the quality of die-castings.

Effect of external forces on microstructural evolution and mechanical properties of high pressure die cast AA5754 alloy

The effects of ultrasonic treatment (UT) and electromagnetic stirring (EMS) forces, individually and in combination, prior to high pressure die-casting of AA5754 alloy were assessed. The liquid of alloy was subjected to UT, EMS and the combined style and then transferred to the shot chamber. The grain size, mechanical properties, gas content and hot tearing susceptibility were analyzed. The results suggest that the application of each process enhances grain refinement and decreases the porosity of the specimens. UT reduces the grain size from 140 to 82 μm and decreases the porosity from 5.5% to 1.4%. EMS reduces the grain size to 107 μm and the porosity to 3.3%. The combination of UT and EMS decreases the grain size and the porosity to 65 μm and 1.1%, respectively, which are the lowest grain size and porosity ever reported for this alloy achieved via physical processing. Intensive cavitation and stirring not only resulted in a refined microstructure but also significantly decreased the hot tearing susceptibility and improved the mechanical properties. All of the aforementioned characteristics are due to cavity formation, during each process. By combination of techniques, EMS could promote the nucleation process by providing more exogenous particles in the strong cavitation field of UT. Ultrasonic plays a major role in grain refining, decreasing the hot tearing susceptibility and the gas content by introducing a strong cavitation field.

Numerical Prediction of Misrun during Filling in High Pressure Die-Casting Process

Numerical Prediction of Misrun during Filling in High Pressure Die-Casting Process