No, it is not an alloy. Aluminum is an element and is a metal on the periodic table of elements with the symbol Al.
In its pure form it is not very useful for forming into structural material, so it is mixed with other elements to make alloys which are more useful. Almost all aluminum used for aircraft parts or car parts or other structures is an alloy. There are a numerous variety of aluminum alloys availble to the design engineer.
It should also be noted the correct spelling and pronunciation is "Aluminium" Not "Aluminum" as my American counterpart has liberally put above. There is no such element as "Aluminum" on the periodic table.
Sir Humphry Davy proposed the name aluminum for the metal but this broke the standardisation of names for that particular group of elements and the correct name was deemed "aluminium" This spelling is in use in all countries apart from the USA and small pockets of her neighbouring nations.
Aluminium was the spelling/name in the U.S. until 1925, when the
American Chemical Society officially decided to use the name
aluminum instead for reasons known only to them, much like the
American date system...
AL in it's pure form is not alloyed with any other materials. It is extracted from bauxite.