High Pressure Die Casting Process Research Articles

Microstructural characterization and analysis of nitinol-based self-healing metals matrix composite of A356 alloy produced by high-pressure die casting

A self-healing non-ferrous metal-matrix composite is prepared by the high-pressure die-casting process. It includes casting set-up, sample preparation of metal matrix composite (MMC), microstructural characterization, and analysis of its ability to close the crack. Aluminum alloy (A356) is deployed as a matrix material in the MMC. Nitinol is a smart alloy produced by a combination of Nickel and Titanium in equal mass proportion. Apart from excellent mechanical properties it also exhibits super-elasticity and shape-memory effect. The wire of the Nitinol is integrated as reinforcement within the matrix of A356 alloy through a high-pressure die-casting process. The recovery percentage of the metal matrix composite and microstructural evaluation are reported. The deployment of shape memory wire provides the ability to recover the matrix material even from plastic strain by just heating the sample slightly above the activation temperature of the Nitinol wire. Microstructural evaluation indicates fair integration of the reinforcement within the matrix material. Gaining the ability for 30.27% angular restoration and 19.37% crack closer is a very positive sign for designing self-healing metallic materials.

Investigation of the Compound Strength of Hybrid Casting Components with Different Variations of Coated and Undercut Sheet Metal

AbstractLightweight design can reduce CO2 emissions and improve energy efficiency, especially in the fuel-intensive transportation sector. Multi-material design approaches can combine specific properties of materials for effective lightweight design. A multi-material component made from two metals used widely in industry could combine the exceptionally lightweight properties of aluminum with the strength and structural integrity of steel. However, joining aluminum and steel is a challenge due to their different thermo-physical properties and the possible formation of brittle intermetallic phases. In hybrid casting, aluminum is cast around a steel sheet insert in a high-pressure die casting process to produce complex parts. In a first approach, a cold gas sprayed aluminum coating on the insert was tested as a bonding agent between the steel substrate and the molten aluminum. The joint was achieved by a combination of metallurgical bonding and micro-clamping. As a second option, surface structures with undercuts were applied to the steel sheet by modified cold rolling, which allowed the molten aluminum to flow into the channels and interlock with the solid steel. Different orientations of the structure on the insert were tested. In addition, the combination of both approaches was used to potentially enhance the positive effect of the pretreatment techniques. Given the critical importance of joint strength, the quality of these approaches was tested by static tensile tests and dynamic fatigue tests. The results show that the joint by coatings is strongly influenced by the process temperature. The improvement of the joint by the surface structure depends on its orientation to the melt flow.

Modifying the Microstructure and Mechanical Properties of Non-Heat Treated HPDC AlSi10MnMg Foundry Alloy via Incorporation of TiB<sub>2</sub> Particles and Sc

The demand for structural lightweight in a variety of industries, particularly the automobile industry, has driven the development of heat-free die-cast aluminum alloys with excellent properties. Utilizing lightweight materials, such as Al-Si alloys has several benefits, including higher overall performance in automobiles and other industries, increased heat resistance efficiency, decreased emissions, and reduced weight. The purpose of this study is to modify the microstructure and enhance the mechanical properties of high-pressure die-casting (HPDC) AlSi10MnMg foundry alloy by incorporation of TiB2 and Sc without any heat treatment. The results showed that the HPDC process significantly refines the grain structure and AlSiMnFe intermetallic compounds, transforming the eutectic morphology from sharp to rounded, and 93% enhancement in elongation at the optimum content (0.018 wt.%) of TiB2. While the hardness of the alloy was improved by 15.7% with the addition of 0.03wt.% TiB2. TiB2 incorporation refines the grain structure and AlSiMnFe phases, while depressing externally solidified crystals (ESCs). The HPDC process refines Al3Sc phases as well as AlSiMnFe phases while increasing yield strength due to Al3Sc strengthening effects. After 0.5wt.% Sc addition in 0.018wt.% TiB2-AlSi10MnMg alloy, the YS, and EL reached the maximum of 196MPa and 9.93% respectively.

Controlling the Fe-intermetallic phases and mechanical properties of secondary Al-9Si-1Fe alloy with Cr and Mn additions

In secondary Al-Si based alloys, microalloying with Mn and Cr can modify harmful platelet-type AlxFeySiz intermetallic phases to less detrimental α-Alx(Fe, Mn, Cr)ySiz phase (script or polygonal morphologies). However, the α-Alx(Fe, Mn, Cr)ySiz phase morphology, phase composition and the addition of Fe-correcting elements can be influenced by solidification conditions. Therefore, this research is aimed to highlight the morphological evolution and mechanisms of α-Alx(Fe, Mn, Cr)ySiz phase in a Cr added Al-9 %Si-1 %Fe-0.2 %Cr (all weight percentage thereafter, unless otherwise stated) alloy with varying Mn concentrations (0.25 %, 0.5 %, and 0.8 %). Microstructure evolution of Fe intermetallic phases is investigated under different casting conditions using a wedge-shaped die, Cu-chill block and melt quenching experiments. Thermodynamic simulations have been performed using CALculation of PHAse Diagrams (CALPHAD) method and compared with the experimental results for phase composition and formation temperatures of α-Alx(Fe, Mn, Cr)ySiz phase. The results indicated that for 0.25Mn-0.2Cr addition to Al-9Si-1Fe alloy, compact morphology containing polygonal phases are formed in Cu-chill casting, while the wedge castings predominantly show a mixed structure with platelets and script type morphologies. Tensile tests revealed a higher elongation value of 6.6 % for mixed structure with platelet and script phases, which is decreased to 4.2 % for polygonal phases in Al-9Si-1Fe-0.2Cr-0.25Mn alloy. This study highlights the importance of solidification conditions on morphologies of Fe-intermetallic phases and the mechanical properties by comparing selected literature relevant to high pressure die-casting process.

Research Progress on Thermal Conductivity of High-Pressure Die-Cast Aluminum Alloys

High-pressure die casting (HPDC) has been extensively used to manufacture aluminum alloy heat dissipation components in the fields of vehicles, electronics, and communication. With the increasing demand for HPDC heat dissipation components, the thermal conductivity of die-cast aluminum alloys is paid more attention. In this paper, a comprehensive review of the research progress on the thermal conductivity of HPDC aluminum alloys is provided. First of all, we introduce the general heat transport mechanism in aluminum alloys, including electrical transport and phonon transport. Secondly, we summarize several common die-cast aluminum alloy systems utilized for heat dissipation components, such as an Al–Si alloy system and silicon-free aluminum alloy systems, along with the corresponding composition optimizations for these alloy systems. Thirdly, the effect of processing parameters, which are significant for the HPDC process, on the thermal conductivity of HPDC aluminum alloys is discussed. Moreover, some heat treatment strategies for enhancing the thermal conductivity of die-cast aluminum alloys are briefly discussed. Apart from experimental findings, a range of theoretical models used to calculate the thermal conductivity of die-cast aluminum alloys are also summarized. This review aims to guide the development of new high-thermal-conductivity die-cast aluminum alloys.

High-pressure die casting process optimization for improving shrinkage porosity and air entrainment in carburetor housing with aluminum alloy using Taguchi-based ProCAST simulation and MADM-based overall quality index

High-pressure die casting process optimization for improving shrinkage porosity and air entrainment in carburetor housing with aluminum alloy using Taguchi-based ProCAST simulation and MADM-based overall quality index

Innovative Hybrid High-Pressure Die-Casting Process for Load-Bearing Body-In-White Structural Components

Innovative Hybrid High-Pressure Die-Casting Process for Load-Bearing Body-In-White Structural Components

Mechanical and Microstructural Investigations on a Symmetric Mould Processed with Semi-Solid Aluminum RheoMetal<sup>TM</sup>: Analysis of the As-Cast Proprieties

High-pressure die-casting (HPDC) can be a productive process for high-quality cast aluminium alloy components. However, it is also a process prone to generate defects, such as gas porosities and incomplete fillings, resulting in rejections. One way to reduce the reject rate is to employ Semi-Solid Metal processing with HPDC. The most important advantages of Semi-Solid alloys are reduced shrinkage defects, fewer gas porosities, and fewer chances of filling-related problems. To take full advantage of a semi-solid metal slurry, the casting process must be controlled meticulously to reach homogeneous casting quality and high process repeatability. A study has been conducted on cast parts composed of two-dimensional symmetrical cavities. From the mechanical tests, unexpected differences emerged in both tensile strength and fracture elongation, which were confirmed by differences in the microstructure. The paper investigates the reasons for the asymmetry in the proprieties to avoid similar problems in future studies and maximize the effectiveness and repeatability of the high-pressure die-casting process.

Analysis of Selected Production Parameters for the Quality of Pressure Castings as a Tool to Increase Competitiveness

The research conducted in the paper highlights the importance of pressure or holding pressure in the mold cavity as a critical production parameter in the high-pressure die casting process for Al-Si alloys. The experiments revealed a direct correlation between the pressure or holding pressure in the mold cavity and the mechanical properties of the castings, including ultimate tensile strength, percentage share of porosity, and the structure of the alloys. The results of the experiments showed that increasing the pressure or holding pressure in the mold cavity led to an increase in ultimate tensile strength and a reduction in the porosity of the castings. The higher pressure or holding pressure also resulted in the elimination of pores in the casting, which further improved its mechanical properties. The increase in ultimate tensile strength and reduction in porosity can be attributed to the better filling of the mold cavity, leading to reduced air entrapment and porosity in the castings. Overall, this paper emphasizes the need for optimizing the technological parameters of the die casting process to ensure the high-quality and efficient production of castings with reduced defects. The results of this study suggest that controlling the pressure or holding pressure in the mold cavity can significantly improve the mechanical properties of the castings, which is essential for achieving the desired quality standards.

Combined defect prediction for large-area die-cast components using high-resolution multi-phase simulation

In the automotive industry there is a trend towards large components that are manufactured using high pressure die casting process (HPDC), in particular when many previously welded individual parts are to be replaced with one cast part to save costs and energy. In the case of large components, incipient solidification during mold filling cannot be ruled out. Casting defects due to cold running, air pockets and porosity cannot be separated spatially and temporally and influence each other. This stronger linking of the defects requires a realistic depiction of the casting process in the simulation, since the interactions between effects are more difficult to depict through approximations. The multi-phase approach presented here offers various options for this: The air is calculated as a compressible gas that is separated from the melt by a sharp boundary surface. Reduced melt flow due to solidification is represented by a porous media approach, followed by a complete flow stop at high solids. The formation of porosity due to volume shrinkage is coupled with a gas evaporation model. The multi-phase approach was validated by casting trials using a specially designed test geometry for thin-walled aluminum HPDC applications. First results of an industrial application are shown.

Tailoring flow behavior and heat transfer in tempering channels for high-pressure die casting—analysis of potentials of commercial static mixers and prospects of additive manufacturing

Additive manufacturing (AM) opens up manifold possibilities to influence the heat transfer between fluid and die in high-pressure die casting (HPDC), eventually allowing to minimize the total cycle time of the process. AM already has been exploited to establish near-contour temperature control systems in industrial applications. However, AM not only allows to influence the position of tempering channels in dies but it also allows to influence the fluid dynamics itself, e.g., by imprinted static mixers. Up to now, such flow-influencing mixing elements have not been considered in metal AM. In the present work, the impact of such metallic static mixers and most relevant processing conditions is investigated experimentally as well by computational fluid dynamics (CFD) simulation. In a first step, conventional static mixer elements are integrated into straight tempering channels to stimulate turbulences of the flowing tempering medium, finally resulting in an increase of the heat transfer up to 33%. In a second step, laser-based powder bed fusion of metals (PBF-LB/M) is applied to realize static mixers. Results obtained reveal that tempering channels without negative influences on the general flow behavior compared to conventional static mixers in straight tempering channels can be realized. In conclusion, the presented results show a positive impact on heat transfer and, thus, allow to further increase the economic efficiency of the HPDC process.

Laser Powder Bed Fusion Tool Repair: Statistical Analysis of 1.2343/H11 Tool Steel Process Parameters and Microstructural Analysis of the Repair Interface

High pressure die casting (HPDC) tools undergo several repairs during their life cycle. Traditional repair methods (e.g., welding) cannot always be applied on damaged tools, necessitating complete replacement. Usually, direct energy deposition (DED) is considered and applied to repair tools. In this study, the potential of laser powder bed fusion (LPBF) for HPDC tool repair is investigated. LPBF of the hot work tool steel 1.2343/H11 normally requires preheating temperatures above 200 °C to overcome cracking. Therefore, a process window for the crack-susceptible hot work tool steel 1.2343/H11 with no preheating was developed to avoid preheating an entire preform. Laser power, hatch distance, and scan speed are varied to maximize relative density. Since the correlation of LPBF process parameters and resulting build quality is not fully understood yet, the relationship between process parameters and surface roughness is statistically determined. The identification of suitable process parameters with no preheating allowed crack-free processing of 1.2343/H11 tool steel via LPBF in this study. The LPBF repair of a volume of ~2000 cm3 was successfully carried out and microstructurally and mechanically characterized. A special focus lays on the interface between the worn HPDC tool and additive reconstruction, since it must withstand the mechanical and thermal loads during the HPDC process.

Technological Optimization of the Stirrup Casting Process with the Use of Computer Simulations.

The article presents the optimization of high-pressure die casting process technology for equestrian stirrups with the application of computer simulation. In the initial stage, the output technology was analyzed, and on the basis of a series of virtual experiments the cause of defects in the casting was highlighted. The optimization process includes different designs of a gating system. Additionally, the casting application properties were evaluated in an exploitation simulation, taking into account predicted defects resulting from the casting and solidification process. Based on the conducted analyses, technological changes were made to the casting technology design allowing the defects occurring in the original technological concept to be removed.

Investigation of the Microstructure and Properties of Aluminum–Copper Compounds Fabricated by the High-Pressure Die Casting Process

The material combination of aluminum and copper is increasingly coming into focus, especially for electrical contact applications. Investigations of different casting processes show that a significant influence for the formation of a material bond is the thermal impact. For high-pressure die casting (HPDC) processes, the impact is quite low, e.g., due to short cycle times. Despite the high efficiency of this technology, currently there are hardly any investigations in this respect. So, the technology was used in this study to produce aluminum–copper compounds and analyze interfacial layers by means of SEM images and EDX measurements. Furthermore, the mechanical and electrical properties of the compounds were determined by means of tensile shear tests and measurements of the electrical conductivity. By modifying specimen geometry, the thermal impact could be increased and, thus, enhanced compound properties were achieved. Overall, compounds of sufficiently high mechanical strength, as well as electrical conductivity, could be produced by HPDC processes, demonstrating the high technical and economic potential of this casting technique.

Shear-accelerated crystallization of glass-forming metallic liquids in high-pressure die casting

• Solidification behavior of Zr 55 Cu 30 Ni 5 Al 10 glass forming liquid under various flow rates was investigated. • Flow-induced crystallization was observed in glass forming liquid as injection rate exceeds 1.1 m/s. • The accelerated crystallization behavior is mainly ascribed to the abrupt perturbation at the end filling stage. • Flow related effect on glass forming ability must be considered in bulk metallic glasses produced by high pressure die casting. 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 Zr 55 Cu 30 Ni 5 Al 10 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.

Influence of Process Parameters on Filling and Feeding Capacity during High-Pressure Die-Casting Process

The quality of high-pressure die casting (HPDC) is largely determined by the process parameters. The objective is to study the influence of process parameters on melt filling and feeding capacity. The research is carried out by means of numerical simulations and orthogonal experiments. The results show that the influence of process parameters is different. The piston velocity of the fast stage has the most obvious impact. As the piston velocity of the fast stage increases, the filling capacity and feeding capacity also increase. The melt injection temperature should not be too low; otherwise, it would be easy to cause gas porosity. The piston velocity of the slow stage should not be too high; otherwise, it would cause air entrainment. The influence of the pressure maintaining time is not obvious due to the ingate solidifying prematurely. The recommended process parameters are a melt injection temperature of 660–680 °C, a piston velocity of 0.1–0.2 m/s in the slow stage, and a piston velocity 2.4–3.2 m/s in the fast stage. This also suggests that appropriate technology should be adopted to delay the solidification time of the ingate in order to realize the feeding effect of pressurization.

Defect band formation in high pressure die casting AE44 magnesium alloy

The characteristics of defect bands in the microstructure of high pressure die casting (HPDC) AE44 magnesium alloy were investigated. Special attention was paid to the effects of process parameters during the HPDC process and casting structure on the distribution of defect bands. Results show that the defect bands are solute segregation bands with the enrichment of Al, Ce and La elements, which are basically in the form of Al11RE3 phase. There is no obvious aggregation of porosities in the defect bands. The width of the inner defect band is 4–8 times larger than that of the outer one. The variation trends of the distribution of the inner and outer defect bands are not consistent under different process parameters and at different locations of castings. This is due to the discrepancy between the formation mechanisms of double defect bands. The filling and solidification behavior of the melt near the chilling layer is very complicated, which finally leads to a fluctuation of the width and location of the outer defect band. By affecting the content and aggregation degree of externally solidified crystals (ESCs) in the cross section of die castings, the process parameters and casting structure have a great influence on the distribution of the inner defect band.

Quench sensitivity of A379 alloy under high-pressure die-casting and gravity-casting processes

Adding Cr to Al–Si–Mg alloys can eliminate the adverse effects of Fe, but can increase the quench sensitivity of the alloys. The influence of gravity-casting and high-pressure die-casting on the quench sensitivity of A379 (Al–7Si–0.5Mg–0.2Cr) alloys were studied using time–temperature–property curves. The nose temperatures of the gravity-casting- and high-pressure die-casting-fabricated specimens are near 350 °C and 355 °C, respectively. The temperature regions with high quench sensitivity characteristics of the former and latter occur from 310 °C to 390 °C and from 290 °C to 400 °C, respectively. The time–temperature–property curves of the high-pressure die-casting-fabricated samples are farther to the left than that of gravity-casting-fabricated samples, indicating that the high-pressure die-casting-fabricated specimens are more sensitive and are easier to generate precipitates than the gravity-casting-fabricated specimens during quenching because of the following reasons. For both specimens, the quench-induced precipitates (Mg xSi) nucleate on the Cr-containing dispersions in the grains, but the Cr-containing dispersions in the high-pressure die-casting-fabricated specimens are finer and more dispersible than in the gravity-casting-fabricated specimens. Meanwhile, the high-pressure die-casting-fabricated specimens exhibited finer grain sizes than the gravity-casting-fabricated specimens; thus, they can provide more grain boundary nucleation sites for forming the Mg xSi phase than the gravity-casting-fabricated specimens during isothermal treatment.

Bonding of cast iron-aluminum in bimetallic castings by high-pressure die casting process

A practical bimetallic casting consisting of aluminum matrix and cast iron inserts was manufactured via high-pressure die casting (HPDC) process. Different surface treatment methods for the cast iron inserts, including salt membrane plating and electrogalvanizing, were adopted to improve the bonding quality of bimetallic castings. Microstructure characterization on the bonding interface was conducted at different locations of bimetallic castings. Results indicate that compounds with flawless and continuously metallurgical bonding interface can be successfully fabricated by the HPDC process with the zinc rack plating treatment on the surface of cast iron inserts which results in a dense zinc coating with an average thickness of 8 μm. The melt flow speed and heat transition during solidification of the HPDC process are two key factors in determining the bonding integrity of bimetallic castings. With the dissolution and diffusion of the very thin zinc coating during solidification, there is no obvious aggregation of zinc element at the metallurgical bonding interface. Instead, a reaction layer with an irregular tongue-like morphology is formed with an average thickness of approximately 1 μm while it mainly consists of intermetallic phases Al60Cu30Fe10, Fe2Al5, and Al2FeSi.

About Residual Stress State of Castings: The Case of HPDC Parts and Possible Advantages through Semi-Solid Processes

Nowadays, one of the most crucial focus in the aluminium-foundry sector is the production of high-quality castings. Mainly, High-Pressure Die Casting (HPDC) is broadly adopted, since by this process is possible to realize aluminium castings with thin walls and high specific mechanical properties. On the other hand, this casting process may cause tensile states into the castings, namely residual stresses. Residual stresses may strongly affect the life of the product causing premature failure of the casting. Various methods can assess these tensile states, but the non-destructive X-Ray method is the most commonly adopted. Namely, in this work, the residual stress analysis has been performed through Sinto-Pulstec μ-X360s. Detailed measurements have been done on powertrain components realized in aluminium alloy EN AC 46000 through HPDC processes to understand and prevent dangerous residual stress state into the aluminium castings. Furthermore, a comparison with stresses induced by Rheocasting processes is underway. In fact, it is well known that Semi-Solid metal forming combines the advantages of casting and forging, solving safety and environmental problems and possibly even the residual stress state can be positively affected.