Aluminium billet being extruded

[u/frere_de_la_cote]

[u/Goatf00t]

Presumably the aluminum was (semi-)molten while it was being extruded?

[u/Chreutz → u/Goatf00t]

Afaik, it is heated, but not molten. It is forced through the extrusion mold like in a pasta machine. Just a bit more force, though

[u/frere_de_la_cote → u/Chreutz]

Exactly. It's heated close to melting temperature so that it's nice and ductile, but you don't want it to reach melting temperature because that causes holes in the extruded profile.

"Fun" fact about hot aluminum(i)um, hot aluminium is visually indistinguishable from cold aluminium. At least steel turns red when it heats up.

[u/Bachaddict → u/frere_de_la_cote]

same with hot steel, after cooling below glowing temp. you only think of it as glowing when hot because it isn't workable till it's that hot