The base metals of Al-3.5Zn-2.2Mg experienced T46 heat treatment have been welded with the filler alloys containing 1.7 w/o Mg and 3.5-6.4 w/o Zn by single pass gas tungsten arc welding (GTAW). The effects of natural aging time on the mechanical properties have been investigated by tensile test and microhardness test. The crack susceptibility has been estimated qualitatively by measuring the length of the crack in the Fish-bone specimen after welding.
The results of the microhardness and tensile test show that the hardness, 0.2% off-set yield strength (Y.S.) and ultimate tensile strength (U.T.S.) increase with increase of the aging time and increase of Zn content in the filler alloy. The fracture in the tensile specimens mainly occurs in the weldment during tensile test.
The U.T.S. and 0.2% off-set Y.S. of weldments welded with filler alloys (Al-5.8Zn-1.6Mg, Al-6.4Zn-1.3Mg) are higher than those of weldments welded with filler alloys currently used. The reason for this is attributed to the higher Zn content in filler alloys. The crack susceptibility of all the filler alloys is ranked as medium.
