Greg has a point there,
there has been someone printing out working firearms, for proof-of-concept use. Also there seems to be an Australian company making jet engine parts by printing.
However, I do agree that heat-treated aluminium might be a tad tricky to do from powder. My on-hand knowledge is from plastic and steel parts, and not high-strength ones. The metal printers said though that the printed stainless steel product does have better strength properties than an untreated cast one and bit less than a machined one. But I was looking at shape and not strength at that point.