Conversation so far:
what is the probable composition of earth's core
The Earth's inner core is believed to consist primarily of an iron–nickel alloy.
what else is made from an iron-nickel alloy besides the earth's inner core
The iron–nickel alloy is the main constituent of the iron planetary cores and iron meteorites.
does the iron-nickel alloy occur on earth's surface
Nickel–iron alloys occur naturally on Earth's surface as telluric or meteoric iron.

Question: what is the alloy used for
Self-contained rewrite: what is the iron-nickel alloy used for