Aluminum

1xxx  Pure Aluminum (≥99% Al)
Excellent corrosion resistance and workability; high thermal/electrical conductivity; low strength. 
-- Electrical conductors, chemical processing equipment, food packaging.  
-- Heat-Treatable? No

2xxx Copper (Cu)
Very high strength-to-weight ratio; good fatigue resistance; lower corrosion resistance. 
-- Aircraft fuselage/wings, aerospace structures, engine pistons. 
Heat-Treatable?  Yes

3xxx Manganese (Mn) 
Moderate strength (stronger than 1xxx); good workability and heat tolerance; good corrosion resistance. ----- Cooking utensils, heat exchangers, general sheet work, beverage cans. 
Heat-Treatable? No

4xxx Silicon (Si) 
Low melting point; high fluidity when molten; good wear resistance. 
-- Welding wire, brazing alloys, engine pistons. 
Heat-Treatable?  Some are

5xxx Magnesium (Mg) 
High strength (of non-heat-treatable alloys); excellent corrosion resistance, especially in saltwater; good weldability. 
-- Marine components, tanks, pressure vessels, automotive parts. Heat-Treatable?
Heat-Treatable? No

6xxx Magnesium and Silicon (Mg, Si) 
Versatile balance of medium strength, good formability, weldability, and corrosion resistance. 
-- Structural applications, architectural extrusions (e.g., window frames), furniture, vehicle frames. 
Heat-Treatable?  Yes

7xxx Zinc (Zn) 
Highest strength available; high performance under stress. 
-- Airframe structures, high-stress parts, military equipment, sporting goods. 
Heat-Treatable? Yes