What aluminum alloy designations indicate that the metal has received no hardening or tempering treatment?

The designation that indicates the aluminum alloy has received no hardening or tempering treatment is associated with the "F" temper designation, as seen in the option. The "F" designation stands for "as fabricated," indicating that the alloy is in its natural, non-heat treated state. This means the metal has undergone minimal processing beyond the basic shaping and forming.

In contrast, the other choices include various temper designations that indicate specific treatments. For instance, "T3" and "T6" temper designations show that those alloys have undergone heat treatment processes to achieve desired mechanical properties, involving processes like solution heat treating and aging. The "O" designation indicates the alloy has been fully annealed, which involves softening the material but does mean it is not suitable for applications requiring specific mechanical strength improvements like its "F" counterpart.

Thus, the correct answer emphasizes the distinction between alloys that have undergone treatment and those that have not, specifically highlighting the properties of the "F" temper.