Tensile strength of MIG-welded 7000 series aluminium alloy extrusions

摘要

7000 series alloys benefit from a high joint strength by the increased strength of the heat-affected softened zone due to natural aging. Comparison was made, for the increased HAZ strength due to natural aging, between the conventional 7N01 alloy and a developed alloy which has recently begun to be employed for automobile bumpers etc. In addition, the effects of filler metal upon the joint strength were investigated. For the developed alloy the strength at the overaged region which was in the heat-affected softened zone was prone to increase due to natural aging, so in some cases fracture took place near the weld junction but the joint efficiency was 95 percent, equal to that of 7N01 alloy in spite of a higher base metal strength than that of 7N01 alloy. Furthermore, the use of an Al-Mg filler metal, which achieves a high weld metal strength, is necessary so that a high joint strength can be obtained for a high strength 7000 series base metal where the strength of the heat-affected softened zone increases due to natural aging.