Form This specification covers an aluminum alloy in the form of coiled sheet 0.010 to 0.249 inch@ incl (0.25 to 6.32 mm@ incl) in thickness@ supplied in the ?CT4 temper (see 8.5). Application These products have been used typically for medium strength parts requiring formability and whose fabrication does not involve welding@ but usage is not limited to such applications. Certain design and processing procedures may cause these products to become susceptible to stress-corrosion cracking; ARP823 recommends practices to minimize such conditions.