Form This specification covers an aluminum alloy in the form of sheet and plate from 0.020 to 1.000 inches (0.51 to 25.4 mm) thick (See 8.3). Application These products have been used typically for formed parts requiring high strength after heat treatment@ but usage is not limited to such applications. Certain design and processing procedures may cause these products to become susceptible to stress-corrosion cracking after heat treatment; ARP823 recommends practices to minimize such conditions.