How much aluminum was used in the Boeing 727?
It may not be possible to provide a precise number for a question with so many variables. Likely, the amount differed between variants. Without speaking to a materials acquisitions director from Boeing in the 70s and 80s, the precise number is probably not available.
That said, this airplane scrapyard website mentions that aluminum accounts for approximately 20% of the weight in a Boeing 747. Going by that same rubric, one might estimate that a 727 would contain approximately 41,900 pounds of aluminum.