Steel is an alloy; does aluminium have alloys?

#1 · February 7, 2024, 7:45 pm

Quote from chief_editor on February 7, 2024, 7:45 pm

Credit: https://aerocommetals.co.uk/

Like steel, which has thousands of different alloys, aluminum has many alloys in many families or classes, typically based around the major alloying ingredient.

Among “wrought” aluminum alloys (alloys meant to be pounded into shape, rather than “cast” by pouring them into molds) the major groups of aluminum alloys are as follows. Within any series there are dozens and hundreds of different alloys varying by composition.

1000 series: almost pure aluminum, these must have 99% aluminum in their mix. They are usually very soft, very thermally and electrically conductive, and very corrosion resistant.

2000 series: aluminum alloys made with copper. Some of the strongest aluminum alloys fall in this group and they used to be favored for aircraft. However, copper severely compromises the corrosion resistance of the materials and they’re prone to cracking under constant stress (“stress corrosion cracking”).

3000 series: alloyed with manganese, these are stronger than the 1000 series, easily welded and shaped, and corrosion resistant. You bump into 3003 aluminum in soda cans every day.

4000 series: primarily alloyed with silicon, which lowers the melting point and increases fluidity of molten metal. It is therefore used when casting parts. (Contradicting my statement that these are the wrought families.) It is also used in brazing and welding applications.

5000 series: these add magnesium for moderate to good strength and fantastic corrosion resistance. They are popular in marine applications.

6000 series: these add both magnesium and silicon. I personally love the 6000 series because some of its members, like the very common 6061, are so forgiving. They’re easy to machine, they can be welded, they can reach good strength, and if you screw up a part then you can always rework and repair it.

7000 series: this series is alloyed with zinc. It has the strongest aluminum alloys and doesn’t have problems with corrosion or cracking that the 2000 series does - at least not to the same extent.

8000 series: all the weirdos that don’t fit in other wrought alloy families go here, like aluminum-lithium alloys.

Cast aluminum alloys follow roughly the same scheme with different numbering:

1xx.x series is mostly pure aluminum

2xx.x series is copper-strengthened

6xx.x series uses magnesium and silicon

7xx.x series uses zinc

etc.

If you scroll through the links I provided, then you’ll see numerous examples of specific alloy numbers and their different compositions.

Another thing to note is that composition isn’t the end of the story. Like a lot of metals, aluminum alloys can be strengthened mechanical work or heat treating. You can stretch or roll aluminum to greater strength (“work hardening”) or causes changes in how the alloying ingredients are mixed, typically causing reinforcements to precipitate out of solution (“precipitation hardening.”)

Credit: https://aerocommetals.co.uk/

Like steel, which has thousands of different alloys, aluminum has many alloys in many families or classes, typically based around the major alloying ingredient.

Among “wrought” aluminum alloys (alloys meant to be pounded into shape, rather than “cast” by pouring them into molds) the major groups of aluminum alloys are as follows. Within any series there are dozens and hundreds of different alloys varying by composition.

1000 series: almost pure aluminum, these must have 99% aluminum in their mix. They are usually very soft, very thermally and electrically conductive, and very corrosion resistant.
2000 series: aluminum alloys made with copper. Some of the strongest aluminum alloys fall in this group and they used to be favored for aircraft. However, copper severely compromises the corrosion resistance of the materials and they’re prone to cracking under constant stress (“stress corrosion cracking”).
3000 series: alloyed with manganese, these are stronger than the 1000 series, easily welded and shaped, and corrosion resistant. You bump into 3003 aluminum in soda cans every day.
4000 series: primarily alloyed with silicon, which lowers the melting point and increases fluidity of molten metal. It is therefore used when casting parts. (Contradicting my statement that these are the wrought families.) It is also used in brazing and welding applications.
5000 series: these add magnesium for moderate to good strength and fantastic corrosion resistance. They are popular in marine applications.
6000 series: these add both magnesium and silicon. I personally love the 6000 series because some of its members, like the very common 6061, are so forgiving. They’re easy to machine, they can be welded, they can reach good strength, and if you screw up a part then you can always rework and repair it.
7000 series: this series is alloyed with zinc. It has the strongest aluminum alloys and doesn’t have problems with corrosion or cracking that the 2000 series does - at least not to the same extent.
8000 series: all the weirdos that don’t fit in other wrought alloy families go here, like aluminum-lithium alloys.

Cast aluminum alloys follow roughly the same scheme with different numbering:

1xx.x series is mostly pure aluminum
2xx.x series is copper-strengthened
6xx.x series uses magnesium and silicon
7xx.x series uses zinc
etc.

If you scroll through the links I provided, then you’ll see numerous examples of specific alloy numbers and their different compositions.

Another thing to note is that composition isn’t the end of the story. Like a lot of metals, aluminum alloys can be strengthened mechanical work or heat treating. You can stretch or roll aluminum to greater strength (“work hardening”) or causes changes in how the alloying ingredients are mixed, typically causing reinforcements to precipitate out of solution (“precipitation hardening.”)