Form: This specification covers an aluminum alloy in the form of extruded bars@ rods@ wire@ shapes@ and tubing. Application: Primarily for parts subject to excessive warpage during machining due to residual stresses@ and for parts requiring high strength and whose fabrication does not normally involve welding. certain design and processing procedures may cause these extrusions to be susceptible to stress-corrosion cracking; ARP 823 recommends practices to minimize such conditions.