A RATIONALIZATION OF FACTORS AFFECTING STRENGTH, DUCTILITY AND TOUGHNESS OF AA6061-TYPE AL-MG-SI-(CU) ALLOYS

The tensile properties and toughness of AA6061-type alloys (nominally Al-1.0% Mg-0.6% Si-0.3% Cu-0.2% Cr) were characterized in terms of the alloy system's solubility relationships at the solutionizing temperat ure. The best combination of strength and ductility is achieved in mat erials with high soluble Mg2Si and excess silicon concentrations. Enha nced ductility at a given strength level is associated with high work hardening rates (n values), whereas toughness is related to intergranu lar (IG) fracture tendencies. Toughness is therefore negatively impact ed by compositional and processing factors that promote IC precipitati on: excess silicon, low solutionizing temperatures, slack quench rates and low dispersoid (Cr/Mn) levels. (C) 1998 Elsevier Science S.A. All rights reserved.