Abstract
The effect of joint line remnant (JLR) on the fatigue lifetime of friction stir welds of a 2198 Al alloy in T851 condition has been assessed experimentally. The base material, sound welds (welded in one sheet) and welds with JLR (produced via welding of two sheets with a natural oxide layer) have been investigated. A strong decrease in microhardness is found for the weak weld zone that is consistent with the reduction in tensile properties compared to the base material: 45% in yield strength and 22% in ultimate tensile strength. The fatigue strengths of sound and JLR bearing welds at 100 000 cycles (R=0·1) are reduced by 10 and 15% respectively compared to the base material. Only for one-third of the JLR bearing specimens, the fatigue crack initiated in regions close to the JLR and this without reduction in fatigue lifetime.