The 4000 series of aluminum alloys mainly use silicon as the main alloying part. Most alloys in this series can be heat treated, but they do not get much stronger. However, alloys that have extra parts like copper (Cu), magnesium (Mg), and nickel (Ni) can get better strength with heat treatment.

These alloys are mainly used to make aluminum alloy welding additives. You can find them in tools like brazing plates, welding rods, and welding wires. The 4000 series is well-known for being strong against wear and having low expansion. It is also good at resisting damage, which makes it great for uses where these traits are important.