Crack susceptibilites of weld crater and weld bead of synthesized-weld-metal Al-2%Zn-3%Mg alloy with and without zirconium up to 0.36% have been evaluated by means of GTA spot weld crater, Houldcroft type and Vatrah weld bead cracking tests.
It was proved that zirconium was beneficial additional element to reduce crack susceptibility of both weld crater and bead with more addition than 0.24%. This beneficial effect of zirconium was closely related with grain refinement of weld structure. The grain refinement of weld bead resulted in the increase in the cracking threshold in BTR, although BTR was not changed.