In this research work, the tribological behaviour of an AZ91D alloy and its composites reinforced with different titanium-based ultra-high-temperature ceramic particulates was investigated. Titanium-based ultra-high-temperature ceramic materials (5 wt%) such as titanium carbide, titanium boride and titanium nitride was used for the fabrication of three different composites, namely ATC, ATB and ATN, respectively. The proposed composites were prepared using a novel ultrasonic treatment-assisted stir-squeeze casting technique. Material characterization was performed using scanning electron microscopy and X-ray diffraction techniques. The porosity and hardness of the composites were determined prior to the wear test. In the pin-on-disc tribometer, the wear test was carried out at room temperature by varying the normal load (12.5–50 N) and the sliding speed (0.25–1 m/s). In addition, at a temperature of up to 200 °C, the tribological behaviour of the composites was assessed. The homogeneous distribution of ultra-high-temperature ceramic particles in the matrix was confirmed by the analysis of the microstructure using scanning electron microscopy images. The X-ray diffraction results showed that the reinforcement materials in the matrix were thermally stable. The hardness of the ATC, ATB and ATN was improved by approximately 31%, 33.8% and 29.6%, respectively. In comparison, at all wear testing conditions, ATB demonstrated superior tribological performance, while the performance of ATN was poor and ATC was moderate. Abrasion, oxidation and delamination were the wear mechanisms at room temperature. At elevated temperatures, oxidation, delamination, thermal softening and plastic deformation wear mechanisms were significant..
In this study, magnesium alloy (AZ91D) matrix composites reinforced with 1 wt% of nano alumina (n-Al 2 O 3 ) were fabricated using novel Ultrasonic Treatment (UST)assisted squeeze casting method. UST was carried out at four different levels of ultrasonic power namely, 0 W (without UST), 1500 W, 2000 W and 2500 W at constant frequency and time. The composites were heat-treated at T6 condition under argon gas protected environment. Microstructural analysis was done using optical microscopy and high-resolution scanning electron microscopy. Physical, mechanical and tribological properties of the composites were evaluated. A significant refinement in grain structure and improvement in porosity was seen on an increase in UST power. Improvement was seen in microhardness, yield strength, ultimate tensile strength and % of elongation of the composite fabricated at 2500 W by 18%, 48%, 28%, and 10% respectively compared to an untreated composite. The composite fabricated at 2500 W showed less wear rate and coefficient of friction when compared to other composites at all sliding conditions. Scanning electron microscope images of the worn surface of the composite pins revealed that the wear mechanisms dominated were abrasion, adhesion, oxidation and delamination.
Aluminium hybrid composites and its machining receives a great attention due to their superior properties like good strength to weight ratio, good castability, machinability, and low cost, suitable for various applications in automotive and aerospace industries. CNC turning is considered as an ideal method for machining of aluminium hybrid composites. Nevertheless, the parameters of turning of aluminium hybrid composites need to be optimized for better and precise machining. Also, the presence of solid lubricants such as Carbon nanotube, Graphite, hexagonal Boron Nitride etc. promotes the machinability of aluminium hybrid composites. In this study, CNC turning on AA6061 matrix based hybrid composites reinforced with Boron carbide (5-15 vol.%) and Carbon nanotube (15 vol.%) was performed. Cutting Speed (rpm):60-180, feed (mm/rev): 0.10-0.20, depth of cut (mm): 0.50-1.00 and percentage of B4C (vol.%) 5-15 were the controlling parameters and responses namely tangential force (N), cutting power (W) and tool wear (mm3/min) were considered for the optimization. Experimental design was made as per Taguchi’s L27 orthogonal array and Grey-fuzzy analytical tool was applied for the optimization. The optimal setting for turning operation on this hybrid composite using Grey-fuzzy analysis were 120 rpm, 0.20 mm/rev, 0.5 mm and 15 vo.% for cutting speed, feed, depth of cut and reinforcement respectively.
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