Friction stir lap welding of 5456 aluminum alloy with different sheet thickness: process optimization and microstructure evolution

Abstract

The influences of friction stir welding process parameters on microstructure evolution and mechanical properties of lap welded 5456 aluminum alloy plates with different thickness and temper conditions were investigated. The upper plate was 5mm thick, cold rolled aluminum alloy 5456-T321 and the lower plate was 2.5mm annealed sheet (5456-O). Four different pin geometries (conical thread pin, cylindrical-conical thread pin, stepped conical thread pin, and Flared Triflute pin tool) and two rotational speeds (600 and 800rpm) were used to produce the joints. Microstructures and microhardness values in the weld nugget (WN), thermomechanically affected zone (TMAZ), and the heat affected zone (HAZ) were examined and correlated with selected processing conditions. Specifically, the influence of tool geometry on the flow of the plasticized material in the nugget zone, extent of hooking defect, and mechanical properties (microhardness) of the FSW joints were documented and quantified.It was found that weld joints made by using the stepped conical thread pin tool produced a homogeneous microstructure with finer grain size (5.4 µm) and higher microhardness levels than the other tools. The optimum processing conditions resulting in sound and defect free joints with highest mechanical properties were obtained with the stepped conical thread pin and 600rpm rotational speed.The evolution of the microhardness in each region is characterized and related to processing conditions.

Influence of the Aluminium Alloy Type on Defects Formation in Friction Stir Lap Welding of Thin Sheets

“…Salari et al [9] claimed that the use of a conical-cylindrical pin might diminish the severity of the lap welding defects when compared to other pin geometries, during welding of AA5456 aluminium alloys. Salari et al [10] corroborated these conclusions and added that controlling the heat input, through an appropriate choice of process parameters, enables to improve the base material stirring across the lap interface. Shirazi et al [11] proved that not only the pin length, but also, the interaction between the pin threads and the tool rotation direction, influence the hook and/or cold lap defects formation.…”

Investigating the Effect of TIG and FSW Joint Design on the Mechanical Properties of the AA5083 Aluminum Alloy in Welding Processes

“…While the hardness in the weld zone in the FSW process is reduced from the base metal to the reinforcement, which can be due to the dissolution of the second phase particles and the unlocking of the dislocations the loss of hardness strain resulting from the rolling structure. In general, the hardness in both welded samples has been reduced by moving from the base metal to the reinforcement, and the hardness in the TIG process is less than that in the FSW process [11][12][13].…”

Mechanical performance research of friction stir welding robot for aerospace applications

“…Salari et al studied the influence of FSW process parameters on the microstructure evolution and mechanical properties of 5456 aluminum alloy sheet under different thickness and tempering conditions. 13 Sekban et al studied the impact toughness of friction stir processed low carbon steel. 14 Khodabakhshi et al studied the residual stress in the bonding process of FSW surface.…”