Form This specification covers an aluminum alloy in the form of sheet and plate from 0.020 to 5.000 inches (0.51 to 127.00 mm)@ inclusive@ in thickness (see 8.5). Application These products have been used typically for parts requiring high strength up to 500 ??(260 ??@ but usage is not limited to such applications. Material may be welded in the specified condition@ but properties are improved by reheat treatment after welding. Reheat treatment after welding@ however@ may reduce resistance to stress-corrosion cracking. Certain design and processing procedures may cause these products to become susceptible to stress-corrosion cracking; ARP823 recommends practices to minimize such conditions.