Impacts of High-Pressure Diecasting Process Parameters on Greenhouse Gas Emissions

In spite of die castings being amongst the highest volume items manufactured by the metalworking industry, the influence of high pressure die casting (HPDC) process parameters on greenhouse gas (GHG) emissions remains largely unreported. In this article, the authors discuss the effect of some HPDC process parameters on GHG emissions using cradle-to-gate life cycle assessment (LCA) for both aluminium and magnesium alloys. Although the impacts reduced with increasing yields in both cases, it was determined that the GHG impact of magnesium alloy HPDC was more sensitive to HPDC yield irrespective of the ratio of primary/secondary alloys in the melt charge. The reasons for this include a greater dependence of magnesium alloy HPDC on high-emitting primary processing and the use of the highly potent GHG SF6 for melting. For magnesium alloy HPDC, a decrease in quality assurance (QA) rejects and cycle times also reduced GHG emissions, although their influences were found to be an order lower than that of yield.

The high-pressure die-casting process can effectively manufacture aluminium alloy castings with complex shapes and thin wall thicknesses. However, due to the complex flow characteristics of the liquid metal during the mould-filling process, there are significant differences in the mechanical properties of different parts of the casting. This paper analyses the effect of the high-speed ram transition position on porosity and mechanical properties of Al-Si-Mn-Mg aluminium alloys in the high-pressure die-casting (HPDC) process, comparing the 1160 mm and 1200 mm positions. Using a comprehensive methodology that combines CT, tensile tests, and SEM, the research demonstrates that the 1160 mm position improves mechanical properties and reduces porosity, with a larger gap at the near-end of the casting, where the yield limit and elongation of the casting increased by 13% and 25% at 1160 mm compared to 1200 mm, respectively. This result shows that appropriate adjustment of the high-speed ram transition position can effectively optimise the organisational structure of thin-walled castings, and then improve their mechanical properties.

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

The article presents the microstructure and mechanical properties of magnesium steering wheels. These steering wheels are manufactured by high pressure die casting. High-pressure die casting (HPDC) is a very good process for making complex mechanical parts out of light metals like magnesium and aluminium alloys. However, in recent times, another light metal has come to the forefront in the quest for lighter vehicles and improved fuel economy. The most commonly used magnesium alloy for die casting automotive components is of the Mg-Al-Mn type. MgAl5Mn is a good purity magnesium alloy with good corrosion resistance, very good mechanical properties and good castability. Mg-Al-Mn based alloys such as MgAl5Mn and MgAl6Mn have better elongation and impact strength than MgAl9Zn, and they are mainly used for auto safety systems like wheel rims and steering wheels. Alloy MgAl5Mn is an alloy with outstanding ductility and energy absorbing properties combined with good strength. This alloy, in the solid state, contains a solid solution α and the intermediate phase Mg17 Al12.

Magnesium is a promising lightweight and green metallic engineering material, but the environmental impact of primary magnesium production stage, especially greenhouse gas (GHG) emissions cannot be ignored. In this study, the life cycle energy consumption and GHG emissions caused by the production of primary magnesium in the years of 2003-2013 in China were calculated; the factor decomposition was conducted to analyze the GHG emissions of magnesium production process by using logarithmic mean Divisia index method (LMDI), including energy GHG emission factors, energy structure, energy consumption per ton of primary magnesium, production, emissions per unit of dolomite and ferrosilicon, and dolomite and ferrosilicon consumptions per ton of primary magnesium. The results showed that GHG emissions of primary magnesium production increased 260.29*104 t CO2eq in total from 2003 to 2013. The variety magnesium production contributed the biggest part of GHG emissions, accounting for 418.17%. The energy structure took second place on the contribution of GHG emissions, accounting for-161.49%. The nest part was energy consumption per ton of primary magnesium, accounting for-138.97%. While, the contribution of energy GHG emission factors, emissions per unit of dolomite and ferrosilicon, and dolomite and ferrosilicon consumptions per ton of primary magnesium was relatively small, which were 0.88%, 0.00% -2.72% -4.73% and-11.13%, respectively. Thus, it is the key methods to reduce GHG emissions by optimizing the energy structure and decreasing the energy consumption.

Two important microstructure characteristics of high pressure die cast magnesium alloy are the externally solidified crystals (ESCs) and the fully divorced eutectic which form at the filling stage of the shot sleeve and at the last stage of solidification in the die cavity, respectively. Both of them have a significant influence on the mechanical properties and performance of magnesium alloy die castings. In the present paper, a numerical model based on the cellular automaton (CA) method was developed to simulate the microstructure evolution of magnesium alloy during cold-chamber high pressure die casting (HPDC) process. Modeling of dendritic growth of magnesium alloy with six-fold symmetry was achieved by defining a special neighbourhood configuration and calculating of the growth kinetics from complete solution of the transport equations. Special attention was paid to establish a nucleation model considering both of the nucleation of externally solidified crystals in the shot sleeve and the massive nucleation in the die cavity. Meanwhile, simulation of the formation of fully divorced eutectic was also taken into account in the present CA model. Validation was performed and the capability of the present model was addressed by comparing the simulated results with those obtained by experiments.

The manufacture of a radio frequency filter box using high pressure die casting (HPDC) is compared to the traditional high speed machining route. This paper describes an industrial exercise that concluded HPDC to be an economical and appropriate method to produce larger volumes of thin-walled telecommunications components. Modifications to the component design were made to make the component suitable for the HPDC process. Development of the die design through simulation modelling is described. The wrought alloy was replaced by near-eutectic Al–Si die casting alloy that was found to give better temperature stability performance. Apart from the economic benefits, HPDC was found to give lower filter efficiency losses through better surface finish. The effects of HPDC process variables, such as intensification pressure and injection piston velocity, on component quality, particularly porosity levels, were investigated. The pressure was analysed in terms of HPDC machine set pressure and the pressure measured in the die cavity by pressure sensors. Porosity was found to decrease with increased pressure and slightly increase with higher casting velocities.

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The high-pressure die-casting (HPDC) process involves injecting molten light metal into a steel mold under high pressure, resulting in parts with excellent surface quality and precise dimensions. However, this process subjects the mold to thermal fatigue and mechanical stress, which can lead to damage over time. This study investigated the wear characteristics of two types of inserts made from different steel materials, SKD61 steel and FDAC steel, under HPDC conditions. A thorough approach that combined computer simulations, experiments, and 3D scanning was employed to analyze wear patterns and dimensional changes after up to 300 casting cycles. The results indicate that the SKD61 steel outperformed the FDAC steel in terms of wear resistance and dimensional stability. The maximum deposition values of the SKD61 mold were only 0.009 mm, which was only 25% compared to the FDAC mold, indicating a significantly higher wear resistance. These findings are crucial for selecting and enhancing insert materials in HPDC, ultimately leading to higher-quality and more efficient casting.

The paper presents the microstructure test results of carbide layers with bond coat obtained on the magnesium alloy with WC/Co – NiCr – AZ91D type thermal spraying method. Layers were sprayed with the APS method on the sandblasted surfaces of approx. 5 mm thick elements manufactured with high pressure die casting (HPDC). The standard process parameters were used for the powders sprayed. The scope of the tests included characteristics of the AZ91D alloy top surface after HPDC process and after sandblasting. The stereometric analysis of surface was performed by using the laser profilometer. The top surface geometric parameters were determined and presented in the form of numbers and topographic maps. Both surfaces were subject to SEM analysis by using the Hitachi S3400N microscope and chemical composition analysis in micro areas (EDX analysis by using the Noran System Six software) to determine presence of impurities and other type of artefacts on the alloy surface before plasma spraying. The alloy surfaces were also subject to detailed tests after spraying process (on lateral micro-sections) to determine the influence of the spraying process on the substrate quality and consequently layer adhesion. Phase composition assessment of the NiCr 80/20 type bond coat and carbide layers WC/10Co and WC/8Co was also performed. Further tests referred to top surface morphology of both carbide layers and chemical composition assessment in micro areas.

The externally solidified crystals (ESCs) in the shot sleeve have a great influence on the final structure of magnesium alloy during cold-chamber high pressure die casting (HPDC) process. In typical HPDC microstructure, a surface layer with uniformly fine grains and a central region containing a mixture of coarse ESCs and fine grains are commonly observed from the cross section of the castings. In the present work, experiments were conducted to investigate the effects of process parameters on the formation of ESCs in the shot sleeve and the final microstructure of magnesium alloy, especially focusing on the grain size, the morphology and distribution of the ESCs. Based on cellular automaton method, a numerical model was developed to simulate the microstructure evolution of magnesium alloy under HPDC process. According to experimental statistics relating the area fraction of the ESCs, a nucleation model was established in which the ESCs in the shot sleeve were taken into account. Simulations were carried out to predict the microstructure of step-shape die castings of AM50 magnesium alloy with different process parameters. It was found that the simulated results were in accordance with the experimental ones.

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