High Pressure Die Casting Research Articles

Critical life cycle inventory for aluminum die casting: A lightweight-vehicle manufacturing enabling technology

Driven by the target of carbon neutrality, the vehicle industry is striving to implement energy conservation and emission reduction (ECER). Aluminum (Al) alloy, which is an effective ECER solution, is the dominant lightweight material for vehicles. Nearly 60% of vehicle Al components are produced by die casting (DC), which can achieve a 30–50% weight reduction. However, Al DC is highly energy intensive and environmentally polluting. It is necessary to assess the life cycle ECER effects of vehicle Al die castings (DCs). However, the existing research weakly supports this assessment, particularly in the manufacturing stage. In addition, the effective implementation of ECER for Al DC is crucial but lacks attractive measures. To bridge these gaps, a system boundary is first defined, including three scenarios: high-pressure DC, high-vacuum DC, and semi-solid DC. A detailed process division and data description are introduced. Then, a thorough inventory analysis is conducted with an in-depth investigation and on-site data collection. Finally, a more representative and configurable inventory compared to existing studies and life cycle assessment databases is provided. It is revealed that the energy consumption in the manufacture of structural DCs is nearly 80% larger than that of box-type DCs. High-vacuum DC and semi-solid DC can reduce the total energy by 3.5% and 9.9%, respectively. Several targeted ECER measures are proposed with intensive analyses and surveys. In addition, the sensitivity of specific Al DCs to the developed inventory is discussed, as are the suggested measures considering energy generation.

Fast aging strengthening by hybrid precipitates in high pressure die-cast Al-Si-Cu-Mg-Zn alloy

The improvement on mechanical properties in high pressure die casting (HPDC) Al Si alloys is an important issue for their application. In this present study, it is found that the artificial aging with low-temperature and short-time can remarkably improve the mechanical properties of HPDC Al-Si-Cu-Mg-Zn alloy, which can avoid heat-treatable defect formation of HPDC Al alloy and be applied in industrial production. The experimental results indicate that the as-cast microstructure of HPDC Al-Si-Cu-Mg-Mn-Zn alloy shows uniformly-distributed GB phases, fine grains and fine AlFeMnSi granular phases. Ascribed to the high cooling rate of HPDC, significant refinement of the obtained microstructure can be achieved. In addition, with the increase of aging temperature from 160 to 220 °C, the θ′ nanoscale phase can be sufficiently precipitated which results in the formation of hybrid precipitates, thus providing a better strengthening effect. The short-time artificial aging at 220 °C for 30 min remarkably improves the hardness of alloy from 115 to 145 HV with an increment of 26.1%. It is found that the hybrid precipitates including β″, Q′ and θ′ are believed to be responsible for such high strengthening contribution by superimposed strengthening in Al-matrix. The Cu-containing nano-precipitates are considered to promote the strengthening of short-time artificial aging in the HPDC Al-Si-Cu-Mg-Zn alloy. The present study provides a feasible and high-efficiency method to prepared HPDC alloy with excellent mechanical properties. • Aging-hardening behavior of HPDC Al-Si-Cu-Mg-Zn alloy was investigated. • Precipitation sequence of aging HPDC Al-Si-Cu-Mg-Zn alloy was elucidated. • Significant improvement on hardness (26.1%) was achieved due to hybrid precipitates. • Precipitation hardening effect on aging HPDC Al-Si-Cu-Mg-Zn alloy was revealed.

Effect of thermo-mechanical treatment and strontium addition on workability and mechanical properties of Al Si Cu casting alloy

In this study, the potential application of Al-Si-Cu aluminum alloy (ALDC12), which is widely used in the high-pressure die-casting (HPDC) process, for fabricating a wrought product was evaluated. The effects of thermo-mechanical treatment and Sr addition on the microstructure, workability, and mechanical properties of the ALDC12 alloy were investigated in detail. The introduction of thermo-mechanical treatment significantly reduced the interconnectivity of the brittle eutectic Si phase formed during solidification and average grain size. Therefore, the uniformly distributed spherical Si particles and fine grain size considerably improved both the strength and ductility of the ALDC12 alloy. Furthermore, the addition of Sr effectively modified the eutectic Si phase in the casting process, which significantly reduced the occurrence of edge cracks in the subsequent rolling step and further improved the mechanical properties of the final sheets. Consequently, through microstructural control of the ALDC12 aluminum alloy by the thermo-mechanical treatment and Sr addition, it was possible to obtain suitable workability and significantly improved mechanical properties compared with those of cast products.

Evaluation of Corrosion Behavior on Crept AlSi10MnMg (AA365) Alloy Produced by High-Pressure Die-Casting (HPDC)

High-pressure die-cast AlSi10MnMg (AA365) alloys have been used as a material for automotive components exposed to high temperature and corrosive environments. This work determines the correlation of corrosion resistance with the intermetallic compounds and micro-voids of crept AA365 alloys under temperatures ranging from 373 K to 573 K with various applied stresses. The results showed that crept AA365 alloy at 473 K possessed a large amount of the intermetallic phases, compared with crept AA365 alloys at 373 K and 573 K due to the non-equilibrium solute atoms in Al matrix. By contrast, crept AA365 alloy at 573 K contained the lowest number of intermetallic precipitates owing to the remelting of the phases. With regard to the corrosion behavior, the corrosion potentials showed −687.0, −684.0, and −673.0 mVSCE of crept AA365 alloys at 373 K, 473 K, and 573 K, respectively, which means the corrosion occurred slowly on the crept AA365 alloy at 573 K, rather than at 373 K, 473 K. The value of the corrosion current density (Icorr) in the crept HPDC AA365 alloy at 473 K has the highest corrosion current density of 13.3 × 10−6 Acm−2, compared with others. It can be inferred that the high amount of intermetallic compounds gave rise to severe corrosion and led to the harmful micro-galvanic corrosion of crept AA365 alloy, rather than the micro-voids.

A Neural Network Based Defect Prediction Approach for Virtual High Pressure Die Casting

Prediction of defects is important to effective process planning for high pressure die casting (HPDC). Current computer aided engineering (CAE) methods of defect prediction are widely used by experienced engineer in industry. However, it is hard for novices to image and understand the underlying relationship between the process and defects. To bridge the gap between training and onsite applications, this paper present a neural network based defect prediction approach (DPA) for virtual HPDC, and details of the DPA development and its implementation in VR are explained. Moreover, a Virtual HPDC Lab is developed as the case study to demonstrate the functionality of DPA proposed, and the result survey verified that the virtual lab with DPA is very much effective for learning and training of HPDC.

Optimization of Process Parameters for Additively Produced Tool Steel 1.2709 with a Layer Thickness of 100 μm.

The purpose of this study was to find and optimize the process parameters of producing tool steel 1.2709 at a layer thickness of 100 μm by DMLS (Direct Metal Laser Sintering). HPDC (High Pressure Die Casting) tools are printed from this material. To date, only layer thicknesses of 20–50 μm are used, and parameters for 100 µm were an undescribed area, according to the state of the art. Increasing the layer thickness could lead to time reduction and higher economic efficiency. The study methodology was divided into several steps. The first step was the research of the single-track 3D printing parameters for the subsequent development of a more accurate description of process parameters. Then, in the second step, volume samples were produced in two campaigns, whose porosity was evaluated by metallographic and CT (computed tomography) analysis. The main requirement for the process parameters was a relative density of the printed material of at least 99.9%, which was achieved and confirmed using the parameters for the production of the samples for the tensile test. Therefore, the results of this article could serve as a methodological procedure for optimizing the parameters to streamline the 3D printing process, and the developed parameters may be used for the productive and quality 3D printing of 1.2709 tool steel.

Enhanced cooling channel efficiency of high-pressure die-casting molds with pure copper linings in cooling channels via explosive bonding

The cooling efficiency of aluminum die-casting molds is critical to prevent soldering, extend mold life and manufacture high quality castings. In this paper, we discuss a method of inserting a pure copper (Cu) lining using explosive expansion bonding process. A pure Cu bush was inserted into a cooling channel of die casting mold and bonded to the inner surface of the cooling channel through explosive bonding technology to form a copper lining in the cooling channel to improve the cooling performance of high pressure die casting (HPDC) mold fabricated from SKD61 material. Furthermore, the microstructure and mechanical properties of the bonding zone between the SKD61 tool steel and pure Cu lining were analyzed. By changing the thickness of the Cu bush, stand-off distance between the Cu bush and the predrilled cooling hole, and mold heat treatment sequence, the optimal explosive bonding process parameters were established for these cases. A high-frequency induction heating-cooling system was used to examine, the performance of the cooling channel sample bonded with pure copper lining, and it was confirmed that the cooling rate was improved by 12 %. After inserting the pure copper lining into the cooling channel for a practical die casting application, it was confirmed that the mold temperature was lowered, and soldering was prevented. The explosive bonding technology used in this study is an effective method to bond pure copper lining onto the inner surface of a cooling channel, thereby providing an alternative approach to increasing the cooling efficiency.

Minimizing the Casting Defects in High Pressure Die Casting Using Taguchi Analysis

High-Pressure Die Casting (HPDC) is one of the major production processes of automotive industry, widely used to manufacture geometrically complex nonferrous castings. The mechanical strength and microstructure of HPDC-manufactured products changes with variation in several process control parameters such as injection pressure, molten temperature, 1st and 2nd stage plunger velocity, cooling temperature, etc. Since these process parameters directly affect casting quality, their optimum combination is needed to maximize the productivity of process and minimize casting defects such as porosity, pinholes, blowholes, inclusions, etc. Hence, to tackle this problem, an approach is presented in this paper that minimizes the major casting defect, i.e., porosity, in the HPDC process by optimizing controlling parameters through Design of Experiments (DOE) in combination with a Taguchi Analysis. The results obtained showed that cooling time, injection pressure, and 2nd stage plunger velocity have a major influence on the response factor (density of the cast part). It was also concluded that, by using a 178 bar injection pressure, 665 °C molten temperature, 5 second cooling time, 210 °C mold temperature, 0.20 m·s−1 1st stage plunger velocity, and 6.0 m·s−1 2nd stage plunger velocity, the rejection rate of the selected part due to porosity was reduced by 61%.

Analysis of local stress/strain fields in an HPDC AM60 plate containing pores with various characteristics

Casting pores are regarded as the main factor causing stress/strain concentrations, facilitating the initiation of microcracks and shortening the plasticity of a cast component. The influence of pore characteristics (i.e., size, morphology, and position) on local stress concentration in a High Pressure Die Cast (HPDC) AM60 sample is studied utilizing X-ray tomography (XRT) and image-based finite element (FE) techniques. Heterogeneous porosity distribution is identified in terms of volume fraction and projected area ratio per segment. Statistically results demonstrate that small pores (volume < 0.01 mm3) have higher number frequency and sphericity. In contrast, large pores (volume > 0.01 mm3) account for a very low number frequency (0.3%), and complex shape. The present study addresses the local stress/strain behavior in a cast-pore containing HPDC AM60 sample during tensile loading investigated using 3D image-based models which consider the actual size, morphology, and spatial distribution of pores based on XRT images and consider the actual material properties of the AM60 alloy. Simulation results show that the local stress/strain around a pore evolves progressively with deformation. The strain at a certain pore location may be amplified or reduced in the presence of other pores, depending on the specific location of the concerning pores. Also, the ratio between the projected area of a pore and its shortest distance to the free surface (PA/SD) could give a good indication of the max local stress concentration around the pore surface. The weakening of Ktpl values of pores found in defect bands are principally due to the pore orientation concerning the load direction. These findings may be extended to provide additional insight into the damage mechanisms in material containing casting pores and to enhance understanding of the ductility variation in terms of local deformation fields around pores and their interactions.

On the Use of Conformal Cooling in High-Pressure Die-Casting and Semisolid Casting

Today, tool life in high pressure die casting (HPDC) is of growing interest. A common agreement is that die life is primarily decided by the thermal load and temperature gradients in the die materials. Conformal cooling with the growth of additive manufacturing has raised interest as a means of extending die life. In the current paper, conformal cooling channels’ performance and effect on the thermal cycle in high-pressure die casting and rheocasting are investigated for conventional HPDC and semisolid processing. It was found that conformal cooling aids die temperature reduction, and the use of die spray may be reduced and support the die-life extension. For the die filling, the increased temperature was possibly counterproductive. Instead, it was found that the main focus for conformal cooling should be focused to manage temperature around the in-let bushing and possibly the runner system. Due to the possible higher inlet pressures for semisolid casting, particular benefits could be seen.

Additive manufacturing of a high strength Al-5Mg2Si-2Mg alloy: Microstructure and mechanical properties

A novel Al-5Mg2Si-2Mg alloy was processed by selective laser melting (SLM) to understand its representative features of microstructural evolution and mechanical properties during additive manufacturing (AM). The as-SLM fabricated Al-5Mg2Si-2Mg alloy is found to deliver much less hot cracks and other defects. Meanwhile, excellent mechanical property is also achieved, i.e. 452 ± 11 MPa for ultimate tensile strength, 295 ± 14 MPa for yield strength, and 9.3 ± 2.5% for elongation. Clearly, these mechanical properties are better than that obtained by high pressure die casting (HPDC), and better than some other alloys obtained by SLM. The as-SLM fabricated Al-5Mg2Si-2Mg alloy is featured by the significantly refined microstructures in the compact primary α-Al, the divorced Mg2Si eutectic networks distributing at α-Al grain boundaries, and some α-AlFeMnSi phase in association with eutectic Mg2Si phase. The high strength and ductility of the alloy are attributed to its unique features including (a) the reduced solidification range, (b) the possible increase of the eutectic level in the microstructure, and (c) the shift of eutectic point and the maximum solubility point of Mg2Si in Al matrix.

RHEINFELDEN CASTASIL-21

Abstract Rheinfelden Castasil-21 (Ci-21, AlSi9Sr) is an aluminum-silicon-iron-strontium high pressure die casting (HPDC) alloy. It was developed by Rheinfelden Alloys GmbH and Co. KG for castings that require an outstanding combination of electrical and/or thermal conductivity. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as casting, heat treating, machining, and joining. Filing Code: Al-476. Producer or source: Rheinfelden Alloys GmbH.

A novel approach to optimize mechanical properties for aluminium alloy in High pressure die casting (HPDC) process combining experiment and modelling

Aimed at the mechanical property improvement in the high pressure die casting (HPDC) process for the aluminium alloy, two sets of shot curves (the baseline and the optimized condition) are designed to study their influence on the distributions of the ultimate tensile strength ( UTS ) and the elongation ( El ) for the as-cast ASTM tensile samples. Difference in the as-cast microstructures and defects are characterized and compared accordingly. Following the experiments, a mathematical model for the entire HPDC process is established to study the characteristics of the melt flow, heat transfer, solidification and defects formation (entrapped gas, oxides, porosities) during the HPDC process with the two above-mentioned piston shot curves are analyzed. The results have shown that the UTS and the El are improved obviously with the optimized shot profile. And the mechanism for these changes are explained in detail. This work provides a novel approach for designing and optimization of metal casting process without conducting excessive experiments and it could be transferred and applied to various alloys systems and different casting processes.

Experimental Study on the Elastic–plastic Transitions of the Hetero-structured High Pressure Die Casting Mg–Al-RE Alloy

High pressure die casting (HPDC) Mg alloy has a hetero-structure in which the microstructures gradually coarsen from the casting surface to the interior, leading to the different elastic–plastic (E-P) transitional behaviors among the layers. In this paper, we quantitively determined the diverse E-P transitions among the HPDC layers and related them to the microstructural evolution. To investigate independently the E-P transitional behavior of the layer, the surface, middle, and central layers were deliberately sliced in sequence from the casting surface to the interior of the HPDC Mg-4Al-5.7RE (in wt.%) component. The onset and the end of E-P transition in each layer were quantitively determined by cyclic tensile test and Kocks-Mecking analysis, respectively. It was found that the plastic deformation for all layers occurred in the first unloading loop near zero strain, indicating the start of the E-P transition. With increasing strain, the E-P transition ended first in the middle layer at 0.0081 strain due to the lowest fraction of the second phases and ended last at the small-grained surface layer at 0.0090 strain. Excluding the twinning-dependent anelastic strain, the E-P transitions ended in advance at the strains of 0.0059 and 0.0062 in the middle and surface layer, respectively. A combination of cyclic tensile test and Kocks-Mecking analysis provided a method to quantitively determine the diverse E-P transitions among the HPDC layers resulted from the hetero-structure regarding grains, the second phases, and twins.

Predicting Quality of Castings via Supervised Learning Method

The process input data which materials processing operations can collect for each unit of production is extensive. Large datasets have long been difficult to work with as computing power to execute analysis in a timely fashion was unavailable. Further, the great velocity at which the data is generated makes near real-time decision-making unwieldy without a new set of tools with which to do the work. When troubleshooting by a small dataset, such as the last few hours of production, observations made on the measured parameters can be misleading. Machine learning is opening doors to high-dimensional data analysis in material processing. In this work, high-pressure die-casting (HPDC) is explored as an exemplar of high-volume materials processing. HPDC process summary data from a full year of production data covering over 950,000 machine cycles is analyzed via supervised machine learning methods to successfully model the prediction of good parts and process scrap as determined by the die-casting machine. Additionally, the prediction of ultimate tensile strength via a classification method of extracted tensile bars is performed and the important features identified are discussed. Supervised learning is found to be a useful tool for materials processing applications.

Macro Porosity Formation: A Study in High Pressure Die 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.

Subsurface Microstructural Evolution of High-Pressure Diecast A365: From Cast to Cold-Sprayed and Heat-Treated Conditions

The use of cold spray deposition, coupled with diffusion-driven thermal postprocessing, is considered herein as a surface modification process such that near-surface microstructural, micromechanical, and microchemical property improvements can be procured for cost-effective and common aluminum alloy castings. Since the present work was an exploratory investigation into the realm of cold spray induced, high-pressure diecast aluminum subsurface property development and evolution, as well as surface modification, one significant aim was to formalize a set of fundamental observations for continued consideration of such an approach to achieving premium aluminum alloy properties from cost-effective alternatives. Nickel, copper, and titanium cold spray modified near-surface regions of the cost-effective high-pressure diecast A365 system was considered. Near-surface, subsurface, and surface evolution was documented across each of the three pure metal coatings. The analysis was continued across two postprocessing coating-substrate atomic diffusion inspired heat-treated conditions as well. Using energy-dispersive X-ray spectroscopy, field-emission scanning electron microscopy, optical microscopy, and various insights gleaned from an original contextualization of the relevant cold spray literature, noteworthy results were recorded and discussed herein. When copper feedstock was employed alongside thermal postprocessing, diverse surface-based intermetallic compounds formed alongside exotic diffusion zones and severely oxidized regions, thus eliminating thermally activated copper cold-sprayed consolidations from future work too. However, both nickel and titanium cold spray surface modification processing demonstrated potential and promise if correct processing stages were performed directly and chronologically. Consequently, a platform is presented for further research on cold sprayed surface microstructural and property modification of cost-effective alloyed aluminum castings.

Failure analysis of H13 steel die for high pressure die casting Al alloy

High pressure die casting (HPDC) die is operated at severe conditions such as high pressure, high temperature and corrosion, which limit its service life. Analysis of failure mechanism of the die is beneficial to guide die design and choose of materials so as to improve the die life. A failed H13 steel die which was used to manufacture a 5G component via Al alloy HPDC, has been investigated using a complementary range of techniques such as X-ray diffractometer (XRD), Optical microscopy (OM), Scanning electron microscopy (SEM), and Transmission electron microscopy (TEM). The results show that erosion and cracking are two main failure modes. Furthermore, the fatal cracking occurs around fillet radius and hole/insert, which is correlated with high local stresses.

Characterization on the formation of porosity and tensile properties prediction in die casting Mg alloys

The 3D visualization of the porosity in high-pressure die casting (HPDC) Mg alloys AZ91D and Mg4Ce2Al0.5Mn (EA42) was investigated by X-ray computed tomography. It was demonstrated that the volumetric porosity at the near-gate location for alloy EA42 was significantly higher than that far from the gate location. This difference resulted from the low valid time during intensified casting pressure conditions. Specimens of alloy EA42 exhibited a narrow pore distribution in the side view (∼0.5 mm) compared to the wide distribution (∼1.8 mm) of alloy AZ91D, which was mainly attributed to the formation mechanism of the defect band. The formation of microporosity in the defect band of alloy EA42 was inhibited because of the significant latent heat released by a large amount of the Al11Ce3 phase segregated in the defect band during solidification. Additionally, an effective estimator (Z-Propagation) was introduced, which is proposed to predict the projected area fraction of the porosity (f) involved during tensile failure with better effectiveness compared with traditional methods based on the actual fractured surface. By coupling the Z-Propagation method with the critical local strain model, the logarithmic fracture strain and true fracture stress of the specimens were predicted within 3.03% and 1.65% of the absolute value of the average relative error (AARE), respectively.

The Influence of Cooling Rate on Microstructure and Mechanical Properties of AlSi9Cu3

The aim of this study was to determine the correlation between the size and the distribution of microstructural constituents and their cooling rate, as well as the correlation between the mechanical properties and the cooling rate of AlSi9Cu3 aluminum alloy when cast in high-pressure die casting (HPDC) conditions. In other words, the ultimate goal of the research was to determine the mechanical properties for a casting at different cooling rates. Castings with different wall thicknesses were chosen, and different cooling rates were assumed for each one. Castings from industrial technological practice were systematically chosen, and probes were extracted from those castings for the characterization of their mechanical properties. Special non-standard cylinders were created on which compressive tests were carried out. The uniqueness of this research lies in the fact that the diameters of the designed cylinders were in direct correlation to the actual wall thickness of the castings. This is important because the solidification of metal in the die cavity is complex, in that the cooling rates are higher on the surface of the casting than in the center. Local in-casting cooling rates were determined using numerical simulations. It was discovered that with increasing cooling rates from 60 K/s to 125 K/s the values for strength at 5% deformation increased on average from 261 MPa to 335 MPa.