A study of superstrengthening and formability in AA3004 alloys

The present study was undertaken to investigate the aging behaviors, the precipitation hardening potentials and the corresponding mechanisms of AA3004 alloy system. The combination effects of the solutes in solid solution, the incoherent second phase particles and the transition precipitates of hardening phases on the mechanical behaviors of AA3004 alloys during cold rolling were examined. The influences of processing sequences on the mechanical property improvement and the texture control of the final gage AA3004 alloy sheets were studied.; The results of this study show that precipitation can occur at temperatures below 500{dollar}spcirc{dollar}F in the properly processed AA3004 alloys. This precipitation can result in a hardening effect which is associated with the formation of intermediate precipitates of Al{dollar}sb2{dollar}CuMg and Mg{dollar}sb2{dollar}Si phases. For an AA3004 alloy with a normal composition, an increase of 14 ksi in the tensile yield strength and 10 ksi in the ultimum tensile strength can be achieved at the O-temper state through a precipitation hardening mechanism. The mechanical properties of the final gage sheets are controlled by the combination effects of several strengthening mechanisms. In the solution treated material a relatively high work hardening rate remains to high strains. In the age hardened materials precipitation of coherent phases results in intense initial work hardening, but the work hardening rate decreases rapidly with strain. The alloy sheets with the best combination of mechanical strength and ductility were produced by the modified processing which includes a high temperature solution treatment followed by rolling-aging-rolling processes. The mechanical strengths achieved through this processing are 50-53 ksi for the tensile yield strength or 53-56 ksi for the ultimum tensile strength. At the same time the ductility remains in the range of 3-4% elongation.; In the modified processing, the high temperature solution treating resulted in a recrystallization texture with similar characteristics established by a conventional anneal or containing a stronger Cube component depending on the heat-up rate used for the solution heating. The overall texture intensity at the final gage state was greatly lowered by the initial Cube texture. The alloy sheets produced through the modified processing give rise to even lower earing (0.87-1.16%) than conventional processing.