5 * * * * system alloy is an aluminum alloy with magnesium as the main alloying element, and belongs to the non heat-treated reinforced aluminum alloy. The alloy has the advantages of small alloy density, high strength ratio of 1 * x x and 3 * x * alloy, high strength aluminum alloy, good fatigue and weldability, good corrosion resistance to marine atmosphere. In order to avoid the stress corrosion produced by high magnesium alloy, the final cold worked products should be stabilized, or the final cold working volume should be controlled, and the temperature should not exceed 65 ℃. the alloy is mainly used for manufacturing welded structures. In the aerospace industry, there are 5A02, 5A03, 5A05, 5B05, 5A06 and so on.

Chemical Composition of 5 series Aerospace Aluminum Alloy
Alloy	Si	Fe	Cu	Mn	Mg	Zn		Ti	Others		Al
									Each	Total
5A02	0.4	0.4	0.1	0.15~0.40	2.0~2.8	－	0.6(Si+Fe)	0.15	0.05	0.15	Remainder
5A03	0.50~0.8	0.5	0.1	0.30~0.6	3.2~3.8	0.2	－	0.15	0.05	0.15	Remainder
5A05	0.5	0.5	0.1	0.30~0.6	4.8~5.5	－	－	－	0.05	0.15	Remainder
5B05	0.4	0.4	0.2	0.20~0.6	4.7~5.7	－	0.6(Si+Fe)	0.15	0.05	0.15	Remainder
5A06	0.4	0.4	0.4	0.50~0.8	5.8~6.8	0.2	0.0001~0.005	0.02~0.10	0.05	0.15	Remainder