The influence of multiple pass submerged friction stir processing on the microstructure and mechanical properties of the FSWED aa6082-aa8011 joints

Abstract

The AA6082–AA8011 friction stir-welded joints were subjected to submerged multiple pass friction stir processing to evaluate the microstructure and mechanical properties of the joints. A maximum of four submerged friction stir processed passes were used in this study. All the specimens were extracted from three different joint positions (start, middle and end). The tests conducted included microstructural analysis, tensile tests, hardness and fracture surface morphology of the post-tensile specimens, were performed using a scanning electron microscope (SEM). There was no particular trend in the microstructure and mechanical properties when looking at the specimen positioning in all the passes. The minimum mean grain sizes were refined from 3.54 to 1.49 µm and the standard deviation from 5.43 to 1.87 µm. The ultimate tensile strength was improved from 84.96 to 94.77 MPa. The four-pass SFSPed specimens were found to have more ductile properties compared to the one-pass SFSPed one. The hardness of the stir zones in all the passes was found to be higher compared to the AA8011 base material but lower than the AA6082 one. The maximum stir zone hardness of 75 HV was observed on the one-pass SFSP joints