Road transport and the associated fuel consumption plays a primary role in emissions. Weight reduction is critical to reaching the targeted reduction of 34% in 2025. Weight reduction in moving parts, such as pistons and brake disc rotors, provide a high-impact route to achieve this goal. The current study aims to investigate the formability of Al–Si alloys reinforced with different fractions and different sizes of SiCp to create an efficient and lightweight Al-MMC brake disk. Lanthanum (La) and cerium (Ce) were added to strengthen the aluminium matrix alloy and to improve the capability of the Al-MMC brake discs to withstand elevated temperature conditions, such as more extended braking periods. La and Ce formed intermetallic phases that further strengthened the composite. The analysis showed the processability and thermal stability of the different material’s combinations: increased particle sizes and broader size range mixture supported the formation of the SiCp particle interactions, acting as an internal scaffolding. In conclusion, the additions of Ce and La strengthened the softer matrix regions and resulted in a doubled compression peak strength of the material without affecting the formability, as demonstrated by the processing maps.
The use of silicon carbide particles (SiCp) as reinforcement in aluminium (Al)-based composites (Al/SiCp) can offer high hardness and high stiffness. The rare-earth elements like lanthanum (La) and cerium (Ce) and transition metals like nickel (Ni) and copper (Cu) were added into the matrix to form intermetallic phases; this is one way to improve the mechanical property of the composite at elevated temperatures. The α-Al15(Fe,Mn)3Si2, Al20(La,Ce)Ti2, and Al11(La,Ce)3, π-Al8FeMg3Si6 phases are formed. Nanoindentation was employed to measure the hardness and elastic modulus of the phases formed in the composite alloys. The rule of mixture was used to predict the modulus of the matrix alloys. The Halpin–Tsai model was applied to calculate the elastic modulus of the particle-reinforced composites. The transition metals (Ni and Cu) and rare-earth elements (La and Ce) determined a 5–15% increase of the elastic modulus of the matrix alloy. The SiC particles increased the elastic modulus of the matrix alloy by 10–15% in composite materials.
One way to improve the mechanical properties of Al-Si alloys is to add chemical modifiers that affect the microstructure of the cast components. Small amounts of Sr cause the modification of the eutectic Si particles from a coarse plate-like morphology into a fine fibrous one. This study sets out to analyse the effects of chemical modification on an Al-7%Si-0.3%Mg foundry alloy treated with Sr, ranging from 62 to 820 ppm. Assessment of modification level was evaluated by both thermal analysis technique and quantitative microstructural investigations. Up to now, little attention has been paid to the role played by microstructural characteristics in evaluating the modification level, which is commonly performed by comparison with standard images. In the present investigation, numerical methods proposed in the literature have been considered in an attempt to understand their effectiveness. The correlation between thermal analysis results and geometrical parameters of eutectic Si particles highlighted the impact of microstructural homogeneity on modification-level evaluation. In addition, the presence of Ca in Srbased intermetallics has been further investigated by means of scanning electron microscopy combined with energy-dispersive X-ray spectroscopy.
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