The effect of oxide impurities on the fluidity of 46000 aluminum alloys, equivalent to A380, was investigated using loop fluidity test. The results indicate that large oxide impurities play a dominant role in fluidity compared to smaller oxides. The large oxide impurities not only result in shorter fluidity length but also increase result variation. Besides, oxides play a negligible role in fluidity when the solid fraction is below a critical threshold. Once the critical solid fraction is reached, large oxides interact with partially solidified grains, blocking the feeding channels between the network of the grains partially or even entirely, depending on the number and size of the oxides. To assess melt quality effectively using fluidity testing, both fluidity length and deviation should be considered.

To enhance the sustainability of aluminum castings, the use of recycled alloys is increasing due to their lower energy demand and reduced carbon footprint. At the same time, semisolid metal (SSM) rheocasting is emerging as a viable alternative to High Pressure Die Casting (HPDC), enabling the processing of low-silicon aluminum alloys. This reduces the need for critical raw materials, such as primary silicon, and allows casting at lower temperatures, further improving efficiency. However, contaminants typically present in recycled alloys, particularly iron, influence castability, defect formation, and mechanical performance, requiring further investigation. This study analyzes the tensile properties and cracking mechanisms of semi-solid cast AlSi7Mg alloys with varying iron content: primary (Fe = 0.08%), recycled (Fe = 0.19%), and recycled high iron (Fe = 0.42%), produced via the Rheometal™ method. Tensile testing was performed on as-cast and T6 samples. Statistical analysis was applied to evaluate variability and statistical significance of the results. The results show that recycled alloys have a higher defect density at an increased iron content, leading to lower elongation, reduced strength, and greater variability than in the primary alloy (recycled alloy Fe=0.19%: as-cast Rp 0.2 =113±8 MPa, R m =208±15 MPa, e f =4.13±0.95 %; T6 Rp 0.2 =240±17 MPa, R m =279±27 MPa, e f =1.40±0.20 %). The T6 treatment improved strength but reduced ductility due to defect enlargement and surface blistering caused by solubilization step, particularly pronounced in the recycled alloy with high-iron content. Scanning electron microscopy (SEM) fractography indicated that oxide films act as nucleation sites for β-Al 5 FeSi intermetallics, which promote shrinkage defects and thereby limit elongation.

Bifilms have been proposed to be critical for forming casting defects. The reduced pressure test (RPT) and bifilm index (BI) have been widely studied and used in industry for melt quality assessment. However, the BI remains challenged in predicting the mechanical properties. This work investigated the usage of RPT for elongation prediction by analyzing the melt in two foundries. The results showed that the BI could be valid when the bifilms exist as fully inflated pores. In reality, bifilms present as pores with various morphology and distribution, generating local stress concentrations under tension. Consequently, the parameter areaeff, which considers the pores’ morphology and distribution, was proposed, and the resultant f eff showed a good correlation with the elongation of the castings. These results guide the foundry to predict the elongation of the final castings and give directions for further research on the bifilm defects.

The influence of Na-Based flux on the melt quality assessment was studied using Density index (DI), bifilm index (BI) and tensile test. The melt was prepared with scrap and ingot with and/or without the addition of Na-based flux. The results show that the addition of Na-based flux decreases the accuracy of the correlation between BI/DI and the hydrogen content due to the increased shrinkage pores. The addition of flux promotes the formation of shrinkage pores by either altering the eutectic solidification behavior or generating more and bigger oxide films which leads to insufficient feeding. Moreover, the addition of flux improves the ductility of specimens by modifying the eutectic phase rather than improving the melt quality.

The surface liquid segregation (SLS) layer in semisolid casting presents higher hardness than the surface of specimens cast using high-pressure die casting (HPDC). Bending fatigue tests showed that semisolid castings present better fatigue properties at higher stress, and this improvement disappears when the applied stress is lower than a critical load. This is because HPDC and SSM castings share the same surface deformation at low stress. More significant deformation is observed for HPDC castings when the stress exceeds the critical load. The presence of surface defects enlarges the difference in deformation at high stress and reduces the critical load.

Treatment of the slurry is important during RheoMetalTM casting. In this work, semi-solid slurries were prepared under different stirring intensities, using two types of stirrers: a naked rod (for regular stirring) and a rod with two blades (for intensified stir). Tensile tests were performed, investigating fracture surfaces, as well as metallographic samples. The results show that intensified stir produces castings with finer primary particles and a more homogeneous microstructure. On the other hand, more faceted Fe-rich phases are found along the α-Al grains boundary as well, due to the dissolution of Fe from the stirrers. Moreover, for intensified stir castings, the porosity found on the fracture surfaces are smaller, while more brittle eutectic phases and second (intermetallic) phases, especially Fe-rich phases, are observed. Consequently, the castings with intensified stir show worse ductility. Finally, a quantitative analysis was made regarding ductility, affected both by porosity and the presence of Fe-rich phases.

Metal casting is an industrially important manufacturing process offering a superior combination of design flexibility, productivity and cost-effectiveness, but has limitations due to filling related defects. Several semisolid casting processes are available capable of casting at a range of solid fractions to overcome this. The current communication aims to review the filling front behaviour and give a new perspective to the gate design in semisolid processing compared to conventional high-pressure die-casting. It is shown that solid fraction and gate widths are critical to avoid instability and spraying.

Two alloys containing different Mg contents have been used to study the combined effect of stirring and oxidation on microstructure and ductility. The results show that intensive stirring can sufficiently disperse the α-Al particles and enable better liquid feeding during solidification and consequently reduce the porosity. The morphology of the oxides is determined by the amount of both Mg and stirring. With lower Mg content, the oxides present as oxide films, which can be broken up during stirring. In alloy with higher Mg content, the oxides exist as particles with numerous cracks, and the particle size increases slightly after stirring. In the Magsimal 59 alloy, due to the presence of large clusters of pores in the fracture surface, the influence of the small oxide particles on the ductility is negligible. In contrast, in the 42000 alloy, large oxide films on the fracture surface are correlated with the ductility.

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.

Semisolid casting can provide excellent castings, but the nature of the pore-forming mechanisms has not been properly clarified. In the current communication, it was suggested that hydrogen precipitated during slurry making might have a decisive role in the formation of both gas and shrinkage porosity. Intensive stirring at the end of the slurry making process may act as a degassing step. Without the intense shearing, structures of primary slurry particles form around the hydrogen pores, strongly affecting pore formation and feeding during the intensification stage.

With the rapid development of smart grid, the combined AC-DC distribution technology is attracting more and more attention. This paper presents a novel topology of combined AC-DC distribution network to solve the problem of the interconnection of the renewable energy and power distribution network. The combined AC-DC distribution network in this paper not only presents a novel mode of coupling and decoupling of renewable energy by using zig-zag transformer but also shows advantages in steady and transient state compared with traditional ac distribution mode. We simulated the novel topology by PSCAD. The simulation results prove the feasibility of the novel topology.