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This research presents the effect of welding speed on dissimilar joints of AA7075-T6 and AA6061-T6 alloys. The weld quality was evaluated through observations of the macrostructure. The mechanical properties of the welds, including the ultimate strength, the percentage of elongation, and the microhardness variations, were determined for different welding speeds. Also the effect of the positions of the two alloys on the mechanical properties was investigated. In addition, during the friction stir welding (FSW) process, the peak temperatures were measured in order to indicate the relation between the peak temperature and the hardness distribution at the heat-affected zone (HAZ). Accordingly, the influence of the welding speed on the developed grain size was elucidated by the microstructural analysis.

A full factorial experimental design was used to assess the importance of the drilling parameters. Digital photography technique was used to evaluate the damages from drilling. The drilling operation was assessed based on two introduced factors, including the delamination factor (DF) and uncut fiber factor (UCFF). Analysis of the experimental results for DF indicated that feed rate was the most significant parameter. On the other sides, experimental results for UCFF showed that feed rate had the greatest influence. Also, the results revealed that the both factors were increased by the increase of feed rate and there was an optimum point of cutting speed and tool diameter in the evaluation of UCFF. Drilling of balsa wood composite sandwich panel had the best quality followed by corrugated foam and PVC foam sandwich panels.

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Friction stir welding (FSW) is a solid state welding process for joining aluminium alloys, has been employed in different industries, and is a new and promising welding process that can produce low-cost and high-quality joints of heat-treatable aluminium alloys because this process uses a non-consumable tool to generate frictional heat in the abutting surfaces and can eliminate some welding defects such as crack and porosity. The various parameters such as rotational speed, welding speed, axial force, and attack angle play vital roles in the FSW process in order to analyse the weld quality. In this research, the impact of processing parameters such as different rotational speed and tool pin profiles on the mechanical, micro-, and macrostructural properties during the FSW process involving the butt jointing of AA7075 T6 is investigated. It is important to note that four-flute and taper threaded pin profiles are utilized and the mechanical characteristics are determined by comparing the ultimate strength, percentage of elongation, and microhardness profiles for different rotational speeds and tool pin profiles.