Influence of tool rotational speed on Microstructure and Mechanical Properties of Al-Li Alloy using Friction Stir Welding

Al-Li alloy is one of the suitable materials to be used in the aerospace industry due to its unique physical, mechanical, fatigue and corrosion resistance properties. The present study investigates the effect of rotational tool speed (TRS) on force and torque and its consequences on heat input, temperature, microstructure, and mechanical properties of a 5 mm thick 2050-T84 Al-Li alloy plates in square butt joint configuration. The investigation reveals defect-free welds at TRS ranging from 600 rpm to 1400 rpm. The grain size at nugget zone (NZ) and thermo-mechanically affected zone (TMAZ) increases (10.59 µm-16.79 µm; TMAZ-AS; 12.67µm-18.96 µm and TMAZ-RS; 12.22 µm-17.98 µm) with an increase in TRS (600–1400 rpm). The high ultimate tensile strength (UTS-410MPa) and % elongation (11.15%) was observed at 1400 rpm. With the help of scanning electron microscope (SEM) analysis of tensile fracture samples, the ductile nature of tensile fracture is observed.