Tensile properties and bendability of T4 treated AA6111 aluminum alloys

The ductility and bendability of the AA6111 aluminum alloy have been investigated as a function of iron content ranging from 0.06 to 0.68wt.%. A significant decrease in ductility (as measured by the reduction of area at fracture) is observed as the iron level increases. Both the low and high iron-containing alloys fail in a shear mode due to void sheeting. The low iron alloy can be bent fully, although it develops significant grooves on the tensile surface linked to shear bands. The high iron alloy, however, develops cracks, running parallel to the bend axis. Both shear bands and cracks propagate along lines of maximum shear, i.e. close to 45° to the maximum tensile direction. These processes are closely linked. Observations suggest that this material is damage-sensitive such that once voids nucleate in shear bands they rapidly develop shear cracks that propagate through a void sheeting process. This results in a significant loss of both tensile ductility (as defined by the reduction of area) and bendability with increasing Fe content.