In this study, the in situ 4 wt.% TiB2(p)/Al-Cu composite was prepared through a mixed salt reaction method. To evaluate its formability, hot isothermal compression tests were performed using a Gleeble−3500 system in a temperature range of 480-510 °C and a strain rate range of 0.1-10 s−1. A constitutive model of the composites with strain compensation was established, and the true stress–strain curves revealed that the composite exhibited favorable formability at 510 °C. Additionally, single-pass equal channel angular pressing (ECAP) processes were conducted at room temperature and 510 °C to investigate the microstructure evolution of the composite. The distribution of TiB2 particles was found to be influenced by deformation temperature, while the microstructural characteristics of the aluminum matrix were minimally affected. Furthermore, a comparison between the as-cast composite and the deformed composites revealed the presence of different preferred orientations in the two conditions, and the corresponding paths of texture evolution were estimated accordingly. Remarkably, after undergoing single-pass ECAP, the Schmid factors of composites remained nearly unchanged, demonstrating that deformed composites were still appropriate for processing and as such demonstrating a potential route also for formability assessment.

Three significant changes are driving the use of materials in the automotive industry today. First, the direct environmental load of materials drives the issue of climate change through the associated carbon footprint of the car from manufacturing to use and end-of-life phases. The new consumer attitudes and legislation force new requirements on the automotive industry. These requirements constitute the second driver, pushing the electrification of the drive line and the use of batteries. The electrification significantly simplifies the car's architecture and allows for a more significant functional integration of the automotive components. This leads to functional integration in component design, considerably changing the conditions to the third driver, consisting of reduced raw material use, material efficiency and recycling and how to achieve cost-effectiveness and resource efficiency. Closing the circle to the climate impact and the carbon footprint changes dramatically. The current paper reviews and analyses the consequences of electrification and the use of Giga casting on aluminium alloys, especially alloying element streams, for recycling in the automotive industry, targeting a near-closed-loop approach. This analysis is made to identify potential resource quality and availability issues for the aluminium alloys and the alloying elements used. It was concluded that there would be a significant need for primary or non-automotive aluminium scrap to be introduced into the flow. All electrified drivelines will allow for a closed-loop scenario where Mg, Si and Mn are the first to reach surplus and Fe, Zn, and Cu are the last. Critical is that the additions of Si made in the recycling process can, in theory, be eliminated. Si is responsible for more than half the carbon footprint of aluminium alloy recycling.

Aluminium metal matrix composites are promising materials for automotive brake discs, and it is critical to assess their wear performance in different braking conditions. This article presents the wear behaviour of aluminium-based composites with different Al-Si matrix alloys added with nickel and copper to retain mechanical strength at high temperatures. The wear tests were conducted at room and high temperatures (250 and 400 °C) to simulate different braking conditions on a pin-on-plate tribometer. The coefficient of friction is in the range of 0.15–0.17 for all materials at room temperature. The specific wear rates of the brake pad and the disc materials indicate that material transfer occurs from the brake pad to the metal counterpart. Microscopy investigations of the wear tracks confirm the material transfer on the composites. It protects the composite surface from wear damage and maintains a stable coefficient of friction. To translate these results into real-world scenarios, the findings of this study suggest that aluminium-based metal matrix composite brake discs have a longer product lifespan compared to the grey cast iron brake discs; the brake pads for the composites would be the components to need replacement due to wear during the product life instead of the brake discs.

A new simple approach was developed to assess the Complete Melt Quality of aluminium cast alloys throughout the production line. The approach relies on the concurrent use of reduced pressure tests (RPT) and tensile tests at each station in the production line when the melt is transferred and/or processed. These tests can be used to determine the source of melt-related problems in the production line. Two case studies from the procedure of both an aluminium die-casting and a rheo-casting plant showed that melts were significantly damaged in the tower furnace and got progressively more damaged through the production line proven by the RPT, tensile test, and fracture surface analysis results.

The relation among process parameters, rheological properties, and the solid fraction of the slurry produced during a Rheo-Metal process for Al-Si alloys is not yet fully understood and contradictory data are available in the literature. There are numerous models that describe the evolution of the rheological properties of a semi-solid material as a function of temperature, applied stresses, and time, which are often based on significant approximations. The Ostwald-de-Waele model, which is the simplest one, assumes viscosity as a function of the shear rate and fluids, whose behaviour is time-independent, whereas the Cross model considers that, at extreme boundary conditions (i.e. at the very low or very high shear rate) thixotropic fluids assume a Newtonian viscosity. The Herschel-Bulkley model is a generalization of the Bingham plastic model and describes the flow of viscoplastic fluids, which exhibit solid behaviour below a certain threshold of yield stress (0) and flow, with linear (Bingham body) or non-linear (Herschel-Bulkley) behaviour, above 0. However, none of these models allows to exhaustively describe simultaneously the behaviour of the slurry in short-term experiments and at the steady state. The static yield strength becomes significantly more dominant with the increase of the solid fraction, until, for values below approximately 0.65 (i.e. at the maximum packaging of the solid particles), the slurry could be treated as a “porous solid body”. So, to model the relation between deformation and stress the use of approaches of continuum mechanics are necessary.

In this study, we developed a model that allows to predict the characteristics of the slurry, using data obtained by a torquemeter connected to the cold solid stirring materials (EEMs) used in rheo-metal processes for slurry preparation. We have studied an AlSi4 and an AlSi7 alloys, preparing the slurries using three different EEMs sizes (5%, 7%, 8% of the total weight of cast) and various rotation speeds of the rod (900 rpm, 1100 rpm, 1200 rpm). To reduce uncertainty factors and to simplify the interpretation of results, we used the same stirring time for each batch on the same alloy, we monitored the actual rotation speed for each sample with a tachometer, and a thermocouple was used to ensure the same initial temperature for the preparation of the semi-solid. The obtained slurries were used to produce tensile test specimens, using a High Pressure Die Casting press. A portion of the specimens was cut, embedded in resin, and prepared for micrographic analyses. These samples were treated with Weck's reagent (4 g KMnO4 and 1 g NaOH in 95 mL distilled water), a colour etching technique aimed at revealing the Si distribution in the cross-section of the -Al particles and distinguishing the solid fraction coming from the slurry from that formed during quenching. The images obtained with the optical microscope were processed using ImageJ processing software. A grid method was applied to calculate the percentage ratio between the number of intersections that fell on the dark and lighter areas of the -Al particles.

Dark areas observed in micrographs correspond to pure Al and were already solid in the slurry, before quenching, while the light areas, containing a higher content of Si, were liquid in the slurry and solidified during quenching. The experimental results evidenced a correlation between the solid fraction and the viscosity of the slurry and a dependence on the size of the EEM used during preparation, especially for the AlSi4 alloy. A good overlap of the data is observed combining the experimental data obtained for the two alloys. Furthermore, a progressive decrease in the dispersion of viscosity values was observed as the solid fraction of the slurry decreased, indicating a system slightly controlled by the interaction between the solid particles. The performed micrographic analysis showed average particle sizes and shape factor values quite dispersed, that fell within the measurement uncertainty. Therefore, these parameters did not explain the observed differences.

Finally, mechanical tests were carried out on the tensile specimens to seek a correlation between the viscosity and solid fraction of the slurry and the mechanical properties of the die-cast components. The study showed a general improvement in the mechanical properties of the specimens as the solid fraction increased, but requires further investigation to reduce the contribution due to the defects present in the component. 

Over the past years, the demand for high-purity aluminium has increased in many sectors, like the aerospace and automotive sectors. This is because aluminium has excellent corrosion resistance and a high strength-to-weight ratio. To cope with this significant increase in demand, the production of primary aluminium has increased since the refining processes of secondary aluminium are limited by high impurities, mainly iron. The iron-rich intermetallic compounds (β-Fe phase) in Al-Si aluminium alloy negatively affect the mechanical properties of the aluminium from its sharp-edged coarse plate structure. In order to mitigate this problem and reduce the iron content in the melt, one way is to add Fe-bearing intermetallic particle formers, like Cr, Mn and Sr. This paper aims to investigate the influence of different Mn additions forlow Fe composition aluminium melt at a constant cooling rate. Specifically, the impact of usingfilters, the Fe removal efficiency for different Mn additions, and the Fe-bearing intermetallic particle’s Fe removal potential. This was done by running small-scale experiments with 8kg/experiment of Al-10Si-0.5Fe (wt%) alloy. The main parameter that varied was the amount of Fe-bearing intermetallic particle formers added to the melt. This report concludes that the Fe-bearing intermetallic parties have mostly sedimented from the top surface of the melt since the composition of the filtered and unfiltered samples were similar. Additionally, larger amounts of Mn are required to improve the Fe removal efficiency for low Fe concentration melt since it improves the Fe removal potential and increases both the size and amount of Fe-bearing intermetallic particles in the melt.

The objective of the present study is to evaluate the hot tearing tendency based on the Clyne and Davies model by evaluating the critical times which can be obtained using a newly developed method. A method to determine the critical times required to calculate the crack susceptibility was presented based on the measurement results with Al–Si alloys, and the method to calculate the crack susceptibility coefficient was presented. In the newly developed method named “Signal intensity method,” signals were generated by tapping the edge of a waveguide which is immersed in molten and solidifying sample and the critical solid fractions were obtained from the signal intensity change. The conventional thermal analysis was also performed simultaneously and the corresponding critical points were identified. The method shown in the present study will enable the determination of the crack susceptibility coefficient with higher accuracy.

The shift towards vehicle electrification must progress while simultaneously addressing sustainability challenges related to lightweighting, which is the intensifying need for high-quality primary aluminium, which demand cannot be met with recycled material with traditional compositional limits. To understand and predict the characteristics of future scrap mixtures, it is crucial to comprehend the evolving composition of new components and associated trends. This insight helps alloy design that accommodates higher impurities and, thus, a more thoughtful strategy for materials process development research. This review delves into the impact of electric motors, batteries, and functional integration. Notably, the analysis herein indicates a rise in magnesium (Mg) and a decrease in copper (Cu) and silicon (Si) contents in the future scrap mixtures due to more Al–Mg alloys such as those found in the 5xxx (Al–Mg) and 6xxx (Al–Mg–Si) series and an outflux of high Al–Si–Cu engine alloys. Gigacastings might counteract this trend based on their Si content and adoption and promote circularity principles by reducing alloy varieties. Reduced Si content in future scrap mixtures is also expected to boost sustainability since significant CO2 emissions from recycled alloys come from melting, controlled by the latent heat of fusion of the scrap mix.