Tensile strength of MIG-welded 7000 series aluminium alloy extrusions

摘要

Al–Zn–Mg 7000 series aluminium alloys are precipitationnhardening type alloys which elevate the strength by heatntreatment but are also epoch-making alloys in which thenstrength of the heat affected softened zone is increasednby natural aging following welding and thus a high jointnstrength can be obtained; 7N01 alloy was developed innJapan and is a typical alloy for welded structures.nIn comparison with Al–Mg 5000 series and Al–nMg–Si 6000 series alloys, 7000 series alloys whichnhave a relatively large quantity of added elements arendisadvantageous due to the consideration required fornaspects of corrosion resistance and recyclability (singlenalloying)1, the latter of which has recently received muchnattention. However, high strength aluminium alloysnare highly attractive due to the need for light weightnstructures and 7000 series alloy extrusions have beennemployed in bumpers and door beams in the automobilensector where the volume of aluminium alloy usage hasnincreased in recent years2.nThe advantages of 7000 series alloys are not only thenhigh base metal strength but also the high joint strengthnachieved by increased strength of the heat-affectednsoftened zone due to post weld natural aging, as previouslyndescribed, and the advantages can be further exploitednby application to welded structures.nThere have been numerous reports3 on 7000 series alloysnfor welded structures and related data on weldability; innthis report variation in the joint strength due to naturalnaging of a newly developed alloy is compared withnthat of the conventional 7N01 alloy and, in addition,nthe effects of filler metal upon the joint strength wereninvestigated.