What aluminum alloy designation indicates no hardening or tempering treatment?

The designation that indicates no hardening or tempering treatment is recognized as “-O,” which denotes the fully annealed condition of the aluminum alloy. In this context, the option that corresponds to this description is 6061-0.

The “0” in the designation indicates that the material has undergone a method of heat treatment and is specifically in the annealed state. This means that the alloy has not been subjected to any aging or hardening processes, making it softer and more workable than its heat-treated counterparts.

Understanding this is crucial in aircraft construction and maintenance, where the selection of material properties directly influences structural integrity and performance. Each aluminum alloy is assigned specific designations based on its composition and processing, impacting its strength, ductility, and other characteristics essential for aviation applications.