9 - A comparative analysis of techniques used for joining intermetallic MMCs

Abstract

Dispersion-strengthened metal matrix composites are used extensively in the development of engineering components, due in part to their high strength-to-weight ratio, high-temperature stability, high creep resistance, high melting point, low density, and corrosion resistance. The addition of a reinforcing phase has led to significant improvements in the mechanical properties of these alloys. However, despite substantial improvements in the properties, the lack of reliable joining methods has restricted their full potential. The differences in physical and metallurgical properties between the intermetallic phase and the matrix prevent the successful application of fusion welding processes, conventionally used for joining monolithic alloys. Therefore, alternative techniques that prevent microstructural changes in the base metal are required. Extensive scientific research has been conducted on joining metal matrix composites reinforced with hard intermetallic compounds. In this study, transient liquid-phase (TLP) diffusion bonding was used to join two pieces of Al 6061 alloy containing 15wt% of Al2O3 particles. Examination of the joint region was achieved using scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. The results indicate that the reactions between the reinforcements, the matrix, and the Ni interlayer lead to the formation of numerous intermetallic compounds in the joint region.