Selected  Problems in Friction Stir Welding of Titanium and Aluminum Armor Grade Alloys

In this paper, authors reported selected problems in friction stir welding (FSW) of 5 mm-thick AA7075-T651 and 3 mm-thick Ti6Al4V. The investigation involved macro and micro-structure analysis and mechanical testing. The welded joints of Ti6Al4V were characterized by the presence of backing plate steel fragments and tungsten particles in the bottom part of the stir zone (SZ) and thermo-mechanically affected zone (TMAZ), which resulted in a relatively low value of joint efficiency (60 %). The investigation on AA7075-T651 was concerned with high-speed FSW (HSFSW) using the MX Triflute tool. In all cases, defective welded joints have been obtained (incomplete root penetration, voids in the SZ) with the best result of joint efficiency of about 59 %.