Aluminum is a critical element of the circular economy as it can be recycled several times. Moreover, Al recycling is a more economically and environmentally efficient procedure than the primary Al production from ores. Secondary aluminum alloys are mostly used in casting applications since it is possible to accommodate their chemical composition through secondary manufacturing processes. However, the quality of the alloys may be considerably altered during the different steps of the recycling process. Inadequate waste sorting might result in excessive contamination. Iron is the most dangerous contaminant because it causes brittle and fragile intermetallic phases, which significantly impacts the mechanical characteristics of alloys. In addition, the microstructure of the alloy changes significantly after multiple cycles of remelting. These issues lead to the downcycling of aluminum, i.e., in other words, the reduction in the overall quality of the alloys. Thus, it has been shown that a number of procedures, including ultrasonic melt treatment and microalloying with rare earths, can somewhat alter the shape of the Fe-rich phases in order to reduce the shortcomings of downcycling. However, a solid mechanical characterization is still missing in order to improve the Fe-rich phase alteration.
Low- pressure casting and high-pressure casting processes are the most common liquid-based technologies used to produce aluminum components. Processing conditions such as cooling rate and pressure level greatly influence the microstructure, mechanical properties, and heat treatment response of the Al alloys produced through these casting techniques. The performance of heat treatment depends on the alloy’s chemical composition and the casting condition such as the vacuum required for high-pressure casting, thus, highlighting the low-pressure casting application that does not require a vacuum. The level of pressure applied to fill the mold cavity can affect the formation of gas porosities and oxide films in the cast. Moreover, mechanical properties are influenced by the microstructure, i.e., secondary dendritic arm spacing, grain size, and the morphology of the secondary phases in the α-matrix. Thus, the current study evaluates the most current research developments performed to reduce these defects and to improve the mechanical performance of the casts produced by low- and high-pressure casting.
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Aluminum structural composites through the infiltration process can be performed by vacuum, centrifugal, or squeeze casting, involving the infiltration of molten Al into fibers, particles, foams, or even porous preforms. This methodology creates hybrid structures of two distinct metal alloys that can be used to locally strengthen components or even to improve the properties of bulk materials, such as ultimate tensile strength and thermal conductivity. New approaches involve the infiltration of liquid Al into a three‐dimensional (3D)‐printed structure of the more rigid metal, such as steel, that the Al matrix. In the current study, stainless steel and copper inserts were produced by fused filament fabrication techniques with various geometries. Moreover, some 3D inserts were electrochemically coated with pure copper to enhance the wettability of the steel insert by Al. Then, the infiltration of these inserts was evaluated by gravity casting, centrifugal casting, and low‐pressure sand casting (LPSC). Evaluations involved microstructural characterization using optical microscopy and SEM for interface analysis. It is revealed that centrifugal casting is highly reliable to infiltrate the inserts with Al, filling detailed cavities in depth. The copper coating aided in the creation of intimate interfaces. The infiltration at the insert's surfaces, curved‐like topography, is obtained through LPSC though it is affected by the direction in respect of material flow.
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