Experimental investigation and optimization of process parameters for friction stir spot welding of dissimilar materials

Abstract

Welding of dissimilar materials using conventional fusion joining techniques has many issues such as formation of brittle crack-prone intermetallic regions, formation of oxides at the weld fusion zone, reduced weld strength at the inner zone of the weld interface and increased consumption rate of material, due to the differences in their metallurgical, physical and mechanical characteristics. Mechanical riveting, fastening using bolts and nuts, tend to increase the overall weight of the finished product and increases the occurrence of crack initiation and propagation through the punctured sheets. Friction stir spot welding poses to be a viable option to effectively join dissimilar materials, as it is a solid state joining process. It is a linear variation of friction stir welding developed in the recent years, which enables fabrication of good quality joints with very minimal post weld machining or cleaning. It is also a consumable free process and energy required is lesser than other joining processes, as the heat produced to soften is concentrated to the weld nugget. Copper (Cu) and Aluminium (Al) material and its alloys possess excellent features such as good conductivity, machining properties, dimensional accuracies and are resistant to corrosion in volatile environments. Aluminium, owing to its good strength to weight ratios, have attracted attention in automobile and electrical industries, in combination with copper, so as to utilize the better properties of both the dissimilar materials. The applicability and research of Cu and Al alloys, have been extended to heavy electrical (power) and electronic manufacturing sectors. newline