Aluminum alloy (АМГ6М) joining by two processes of friction-stir and non-consumable Tungsten electrode welding and comparison of their mechanical and microstructure properties

The purpose of this research is to investigate the possibility of replacement of arc welding under shielding gas with non-consumable Tungsten electrode (TIG) of Al АМГ6М alloy by friction stir welding (FSW). In this regard, after applying primary parameters for both welding processes to obtain optimum parameters, the prepared samples were characterized with Tension, bending, radiography, hardness and distortion tests and also microstructure evaluation. The results of this study showed that the grain size of welding zone of TIG and FSW processes are 14 and 6 µm respectively, which are smaller than the base metal with 30 µm in size. The ultimate tensile strength of the FSW joints in the parallel to rolling direction and in the vertical direction with welding line is much more higher than TIG joints; 364 Mpa versus 278 Mpa. The reduction of microhardness in the welding zone for both process FSW and TIG have been in a range. The amount of distortion measured in the FSW was one-fourth of these values in TIG. The result of bending test of the FSW sample from the plane like to the results of the base metal is crack free. Therefore, in order to improve the mechanical and metallurgical properties, as well as to reduce weld joints distortion in aluminum structures, FSW was considered an appropriate alternative to the replacement of the arc welding under shielding gas with non-consumable tungsten electrode.