Effect of Tool Geometry in the Friction Stir Welding of AA6082-T651

Abstract

The Friction Stir Welding (FSW) process has a large industrial potential in the field of joining lightweight alloys. Due to the increasing industrial use of aluminium alloys the benefits provided by this technology are very appealing. However, this potential has not, until this time, become a reality due to the lack of relevant available information concerning the process. The lack of information is especially serious in regards to the welding tools. This component, whose importance in the FSW process cannot be overstated, has not been the subject of extensive published research due mainly to the difficulties related to the modelling of the FSW process, which means that all of the development in this field has to be conducted through a trial and error approach. This approach entails significant costs and success risks, thus reducing the capability of R&D institutions to carry out extensive research. The objective behind the work detailed in this paper is the assessment of the effects of the welding tool geometry and features in the weld quality and process productivity. The work was carried out via an experimental procedure, which consisted of carrying out several welds using different pin lengths, pin diameter, pin geometry and shoulder diameter. The geometries that were used are based on known geometries from literature and new concepts. Due to practical limitations the study was conducted using a 3mm thick AA 6082-T6 butt joint configuration. The quality of the welds was assessed through destructive and non destructive testing, namely a visual inspection, an x-ray and a macrographic examination. These results can then be used to correlate the effects of the different tool geometries with the weld quality and productivity. The process productivity can be, according to [1], directly related to the welding speed, this is due to the near absence of welding consumables in the FSW process, leading to the predominance of fixed costs. The results pertaining to this work enable a better comprehension of the manner by which the tool geometry influences the weld quality and the process productivity, thus providing a stepping stone in the ongoing task of optimizing and modelling of the FSW process. The results presented in this paper may also be useful when extrapolated to other materials and thicknesses.