Mechanical Property and Structures of Friction-Stir Weld Joint of 2195-T8 Al-Li Alloy Plate

Abstract:

The tensile properties of friction stir weld (FSW) joint of 2195-T8 Al-Li alloy plate with 5 mm thickness prepared by straight cylindrical pin and threaded cylindrical pin at different rotational speed and welding speed were investigated. The structures of the FSW joint were detected. As prepared by straight cylindrical pin at improper welding speed, continuous hole was formed in the FSW joint along the welding direction, leading to lower joint strength. Threaded cylindrical pin alleviated the formation of hole in the weld, and the joint strength was increased with the rotational speed increasing from 700 r/min to 1100 r/min. The grains in the nugget zone (NZ) were recrystallized, and their size was decreased along the direction from the top to the bottom. Meanwhile, the grain size in the NZ adjacent to the thermo-mechanically affect zone (TMAZ) was smaller than that in the central NZ. The precipitates of T1 (Al₂CuLi) and q￠ (Al₂Cu) in the NZ were completely dissolved. All q￠ precipitates but most T1 precipitates were dissolved in the TMAZ. Meanwhile, dislocations were formed in the NZ.

Key words:2195 Al-Li alloy; friction stir weld (FSW); mechanical Properties; structures