Investigation on Microstructural and Mechanical Properties of Microwave Welded Al6061-SiC-Graphite Hybrid Metal Matrix Composites

In the present work, the microstructure and mechanical properties of microwave welded Al6061-6%Graphite-SiC hybrid metal matrix composites (MMC) were investigated. The microwave welding was carried out using the principle of microwave hybrid heating and Al6061 powder as an interfacial material. The domestic microwave oven having the frequency of 2.45 GHz and 900 W power was used for the experiments. The charcoal powder as a susceptor was used during the welding process. The hybrid MMCs Al6061-6%Gr-SiC were developed through stir casting process with different weight percentage of SiC keeping graphite constant. The joints were characterized using x-ray diffraction, scanning electron microscope (SEM) equipped with energy-dispersive spectrum (EDS), Rockwell hardness tester and universal testing machine. The x-ray diffraction analysis showed the presence of harder aluminum carbide and aluminum oxide phases. The microstructural study revealed the good metallurgical bonding between the interfacial composites with absence of cracks. The elemental analysis of joint revealed the presence of aluminum, carbon and oxygen with other elements. The average ultimate tensile strength of the microwave joints was recorded as 135 MPa with 4.3% elongation. The average Rockwell hardness at the weld joint observed was 61.5 ± 5 HRB. The evaluation of mechanical properties of microwave welded composites indicated the increase in the tensile strength and hardness as the content of SiC reinforcement increased. The joint strength found to be 65.15% of parent composite, which is similar to the joint strength of welded aluminum-based composites by various techniques such as friction stir welding, laser beam welding, electron beam welding, etc. The present investigation has showed that the microwave energy can be used successfully, as an alternative method to weld the composites.