Mechanical behavior of 7085-T7452 aluminum alloy thick plate joint produced by double-sided friction stir welding: Effect of welding parameters and strain rates

Mechanical behavior of double-sided friction stir welding (DS-FSW) aluminum alloy thick plate joints under various rotational rates and welding speeds tested at different strain rates were investigated. The results show that both the yield stress (YS) and the elongation to failure of DS-FSW joints increase, but the ultimate tensile strength (UTS) of defect-free joints decrease with the decrease of strain rate from 10⁻² s⁻¹ to 10⁻⁵ s⁻¹. A remarkable reduction in the YS, UTS and elongation to failure presents, particularly at the top slice of 950/60 joint, reaching approximately 65%, 68% and 25% of the BM tested at a strain rate of 10⁻⁴ s⁻¹and fails through brittle fracture. The top slice presents the highest strength and the middle slice has the largest ductility, the same as change laws of joint efficiency and strain hardening behavior among three slices. The best welding parameters is the rotational rate of 300 rpm and welding speed of 60 mm/min due to the higher and the smaller fluctuation of strength and ductility for different slices.