Effect of Pre and Post Weld Heat Treatment on the Mechanical Properties of Friction Stir Welded AA6061-T6 Joint

Abstract

This research work focuses on the study of the improvement of mechanical properties, specifically the tensile strength of 6061-T6 aluminum alloy on prismatic specimens with 9.5 mm thickness that has been subjected to friction stir welding process and two heat treatments; solubilized and aging before or after the welding process. Three cases studied and evaluated were, welding of the base material without heat treatment (BMW), solubilized heat treatment and partial aging of the base material before welding (HTBW), and heat treatment of solubilized and aging of the base material after welding (HTAW). The obtained results show an increase of about 10% (20 MPa) of tensile strength for the HTBW process, compared to BMW case. In addition, for the case of HTAW, the obtained tensile resistance presents a joint efficiency of 96%, which is close to the tensile strength of the base material (»310 MPa).

Studies on Quality of Joints and Phenomena Therein for Welded Vehicle Components Made of Aluminium Alloy – a Review

“…Studying FSWed joints of 6061-T6 alloy (Table 3), Juarez et al [316] reported that the surface fracture surfaces of tensile specimens, for the welding without heat treatment BMW and solubilized heat treatment and partial aging before welding HTBW cases, most of the fractures occurred on the AS of the tool and in the heat-affected zone. Fracture appeared on the unaffected material zone UFM and RS for the solubilized heat treatment and aging after welding HTAW case.…”

“…The FSWed joints of 6061-T6 alloy (Table 4), studied by Juarez et al [316] were obtained at constant TRS of 1000 rpm, WS of 90 mm/min, penetration speed of 9 mm/min, and holding time of 10 seconds. The last parameters allowed lowering the defects of welding.…”

“…The proper FSWed joints of 6061-T6 alloy (Table 5), studied by Juarez et al [316] were obtained using tool with flat shoulder diameter of 25.4 mm, composite pin with a hexagonal shank with a maximum diameter of 8 mm and a length of 9 mm and a cylindrical collar with a diameter of 11 mm and a height of 3 mm made of H13 steel.…”

“…For FSWed joints of 6061-T6 alloy Juarez et al [316] noticed four characteristic zones of friction welding including agitation zone (stir zone), TMAZ, HAZ and unaffected material UFM. The fracture surfaces of tension specimens revealed the micro-voids present in the fracture zones for the three cases BMW, HTBW and HTAW.…”

“…Studying FSWed joints of 6061-T6 alloy Juarez et al [316] reported that the micro-hardness at the stir zone was of 85 HV for the base material welded BMW, 109 HV for the material with heat treatment before welding HTBW, and 134 HV for the material with heat treatment after welding HTAW. For the case of HTAW, the micro-hardness exhibited the lowest dispersion of values between 124 HV and 148 HV along the four characteristic zones.…”