Harikishor Kumar

For the busting of heat, generated in electronic packages, relevant materials need to be developed. Metal matrix composites may be considered as an option to tailor the properties of a material (Cu) by incorporating an additional phase (SiC) for fulfilling the requirements of thermal management systems. The composite (Cu/SiC) was manufactured by friction stir processing. For good interfacial strength, the biggest challenge in the fabrication of Cu/SiC composite was to abolish the reaction between Cu and SiC. Being solid in nature, the process (friction stir processing) does not allow temperature to reach the interfacial interaction. Scanning electron microscopy, electron backscattered diffraction, and optical microscopy were used to characterise the composite for microstructural features (particle dispersion, phases present). To confirm the presence of reinforcement, EDS analysis was also performed on the composite. Results indicated the presence of Cu and SiC phases in the stir zone (SZ) with uniform and homogeneous separation of reinforcements. The composite displayed higher hardness, tensile strength, and wear resistance in comparison to unprocessed copper. However, ductility decreased due to high hardness in the composite.

Despite excellent properties of aluminium silicon (Al-Si) alloys in several aircraft and automotive applications, its usage is limited because near net shape casting of Al-Si alloys may cause several defects like surface pinholes and grooves. Fabrication of components and then welding them via fusion-based welding processes imposes issues like porosity and slag inclusions which may severely degrades its properties. Thus in present study, friction stir welding (FSW) was employed for welding of hypereutectic Al-Si cast alloy. The nugget zone (NZ) of welded alloy and its as-cast counterparts were characterized for their performance in terms of mechanical and tribological behaviour. The results depicted fragmentation of α-Al dendrites, refinement and redistribution of acicular Si particles as a result of stirring with high strain rate, and improvement in mechanical properties such as ultimate tensile strength, yield strength, ductility, hardness and wear resistance as compared to as-cast alloy. It is also shown that disparate wear mechanisms occured in friction stir welded (FSWed) and as-cast alloys. A sizeable amount of adhesion with plastic deformation and delamination pits were observed for as-cast alloy, while the dominant mechanism in FSWed alloy was peeling with little adhesion.

The present work aims to develop Cu/ZrO₂ surface composite by friction stir processing and analyse the effect of zirconia incorporation on microstructure, mechanical, and tribological behaviour of developed copper matrix composite. Microstructural observations indicated that grains were equiaxed and fine in the stir zone of the composite and zirconia particles were uniformly dispersed in the copper matrix with excellent bonding. The test results for mechanical and wear behaviour showed increment in hardness and wear resistance as compared to copper which may be because of the effect of zirconia presence and grain refinement. The fabricated composite displayed higher value of average friction coefficient in comparison to as received copper. The worn surface observed by SEM revealed the predominance of adhesion and delamination wear mechanism in base copper.

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