Form This specification covers an aluminum alloy in the form of die forgings not over 3 inches (76 mm) and hand forgings up to 6 inches (150 mm)@ inclusive in nominal thickness at the time of heat treatment@ and forging stock of any size (see 8.6). Application These products have been used typically for parts requiring a high level of mechanical properties and good resistance to stress-corrosion cracking@ but usage is not limited to such applications.