Sequential procedure to investigate the optimal ranges of process parameters for the FSW of AA8090

Abstract

The main purpose of this experiment is to evaluate the optimum range of process parameters for Friction Stir welding of AA8090. In the present research work, an experiment has been made to join AA8090 alloy using friction stir welding (FSW) at different rotational speed, welding speed and tilt angle settings. The FSW was done on the CNC (Computer Numeric Control) Vertical milling machine using fixture and a cylindrical threaded tool. For designing experiments, the steepest ascent technique (Factorial Design) was used considering tilt angle, welding speed and rotational speed as input parameters and ultimate tensile strength (UTS) as an output parameter. The metallurgical and mechanical characteristics were investigated and considered while providing the sequential procedure for the optimal range. The optimum range of values observed at tilt angle (1.1° to 1.9°), welding speed (24.6 to 48.2 mm min−1), and rotational speed (1428 to 1876 r min−1). The maximum value of UTS (365 MPa) is obtained at rotational speed of 1652 r min−1, welding speed of 36.4 mm min−1, and tilt angle of 1.5°. Scanning electron microscopy and optical microscope were used for fractrography and microstructural analyses of the joints. The finer grains are observed in the NZ equated to the HAZ and TMAZ.