Aluminium metal matrix composites (AMMCs) using alumina (Al₂O₃) and silicon carbide (SiC) as reinforcement elements are gaining significant interest in various applications because of their excellent properties. In this study, Al₂O₃/SiC with compositions (0.5 wt.%, 1.5 wt.%, and 2.5 wt.% for each) were used as reinforcement elements in an aluminium alloy (AA2024-T6). The samples prepared were AA2024-T6 + (0.5Al₂O₃/0.5SiC), AA2024-T6 + (1.5Al₂O₃/1.5SiC), and AA2024-T6 + (2.5Al₂O₃/2.5SiC) using a stir-casting technique. The experimental study included density calculation mechanical properties, such as tensile strength, compressive strength and hardness. The study also included a microstructure examination of the fracture surface of the tensile specimens. The results showed that incorporating Al₂O₃/SiC as reinforcement materials into aluminium AA2024-T6 significantly improved its properties. Hence, increasing the reinforcement with compositions of 2.5Al₂O₃/2.5SiC into AA2024-T6 showed a drop in density and increased mechanical properties, such as ultimate tensile strength, compressive strength and hardness, compared to the base alloy (AA2024-T6). Furthermore, the scanning electron microscopy analysis revealed the uniform distribution of the reinforcement particles resulting in strong bonding with the matrix. The findings suggest that Al₂O₃/SiC reinforced with AA2024-T6 can be used in applications where a combination of lightweight and high strength is needed.

Given the rising consumption of plastic products, it is becoming imperative to prioritize the recycling of plastic items as a solution to reducing plastic waste and environmental pollution. In this context, this research focuses on assessing the impact of incorporating rice husk and wood flour into recycled high-density polyethylene (rec-HDPE) to analyze its mechanical properties, flammability, and thermal stability. The combined rec-HDPE content of wood flour and rice husk varied between 0% and 20%. The rec-HDPE content of maleic anhydride grafted polyethylene (MAPE) was fixed at 3%. Mechanical characteristics such as flexural, tensile, and impact strengths were assessed. Cone calorimetry (CC) tests, limited oxygen index (LOI) tests, and horizontal and vertical burning tests were performed to determine the flammability or fire retardancy of these composites. On the other hand, to characterize the thermal characteristics of these composites, thermogravimetric analysis (TGA) was used. To further characterize the fluctuation in these characteristics, scanning electron microscopy (SEM) and infrared spectroscopy (FTIR) studies were carried out. The mechanical characteristics were found to be increased in response to adding rice husk or wood flour. An 8% increase in tensile strength and a 20% increase in elastic modulus enhancement were recorded for a 20% rice husk-added composite. SEM revealed the reason for the variation in tensile properties, based on the extent of agglomeration and the extent of uniform distribution of fillers in rec-HDPE. Following these lines, the 20% rice husk-added composite also showed a maximum increase of around 6% in its flexural strength and a maximum increase of 50% in its flexural modulus. A decrease in impact strength was recorded for rice husk and wood flour-reinforced composites, compared with unreinforced rec-HDPE. Hybrid composites displayed a lack of mechanical strength due to changes in their nature. FTIR tests were performed for a much more elaborate analysis to confirm these results. Twenty percent of rice husk-added rec-HDPE displayed the best thermal properties that were tested, based on TGA and derivative thermogravimetric (DTG) analysis. This 20% composite also displayed the best fire-retardancy characteristics according to UL 94 tests, cone calorimetry tests, and limited oxygen index tests, due to the barrier created by the silica protective layer. These tests demonstrated that the incorporation of both fillers—rice husk and wood flour—effectively enhanced the thermal, mechanical, and fire-retardant attributes of recycled HDPE.

Machining, particularly drilling, plays a significant role in various industries, including aerospace and automotive, where efficient drilling is a critical factor in their operational success. However, low-quality holes can result in structural failures and increase production costs. Achieving high-quality holes necessitates appropriate selection of drilling tools, process parameters, and machine setup conditions. This study investigates the impact of drilling parameters, specifically feed rate and spindle speed, on chip formation and hole quality, including deviations from normal size, circularity, cylindricity, perpendicularity, and surface roughness. Experiments were conducted on aluminum alloy 2024-T6 (AA2024-T6), a widely used material in the aerospace industry. This paper investigated the drilling process parameters using uncoated high-strength stainless steel (HSS) and cobalt-coated high-strength stainless steel (HSS-Co) drill bits, with a 30° helix angle and 140° point angle, under both dry and cryogenic conditions with liquid nitrogen (boiling point: − 195.8 °C). Results demonstrated that HSS drill bits, in cryogenic conditions, produce holes with lower surface roughness, minimal deviation from nominal size, and reduced errors in circularity, cylindricity, and perpendicularity compared to those made under dry conditions. Conversely, HSS-Co drill bits yielded high-quality holes under dry conditions across all feed rates and spindle speeds. Furthermore, short and segmented chips were formed at high feed rates and low spindle speeds. No significant variations were observed in the chip’s formation for both HSS and HSS-Co drills. Additionally, scanning electron microscopy (SEM) was used to examine the internal defects of the drilled holes, providing further insight into the impact of drilling conditions on hole quality.