I don't know how this is made and I don't know the name of the method to search for it to learn more.
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Aluminum sections are extruded from billets heated to 800-925F under high pressure and then pushed through a die.
During the entire process temperature is carefully controlled, because depending on the aluminum alloy and performance expected heat stages at the beginning and exit out of die are crucial.
here is the diagram of the extrusion machine.