Form This specification covers an aluminum alloy in the form of extruded bars@ rods@ wire@ profiles@ and tubing up to 2.999 inches@ incl (76.17 mm@ incl) in thickness@ nominal diameter or wall thickness with cross-sectional area 25 in2 (161 cm2) and under (see 8.5). Application These extrusions have been used typically for structural parts requiring high strength up to 500 ??(260 ?? after proper precipitation heat treatment and which may require welding during fabrication@ but usage is not limited to such applications. Certain design and fabricating procedures may cause extrusions in the specified condition to become susceptible to stress-corrosion cracking; ARP823 recommends practices to minimize such conditions.