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Aluminum alloy sheets are used for automotive body-panels, but their small Young's modulus results in inferior shape-fixability than conventionally-applied steel sheets with similar strengths. Smaller radius of curvature, indicating better shape-fixability, is found at the center of a panel press-formed with higher blank holder force (BHF). Higher force can be applied for press-forming of alloy sheets with larger strain-hardening exponent (n value) induced by an increased addition of Mg. Recently-developed 5000 series alloy sheets containing 5.5 pct Mg and 0.3 pct Cu have an elongation over 33 pct at an ultimate tensile strength of 270 MPa and can be press-formed with better shape-fixability.

Al-Mg-Cu alloys have been developed for auto body components. The improved characteristics are obtained by using a continuous annealing line (CAL) and applying final ageing. Rapid heating, high annealing temperature and rapid cooling of CAL dissolves Cu precipitates and recrystallizes in grains of suitable sizes to prevent stretcher strain marking free (SSP). The improved formability and increased strength after final ageing are due to the Cu dissolution by CAL. Other fabrication practices were also studied. The paint bake properties are better than 5182-0 and the formability of these alloys do not change during long storage. Other properties such as weld-ability and corrosion resistance are almost comparable or superior.