Effect of joint line remnant on fatigue lifetime of friction stir welded Al–Cu–Li alloy

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.