Of course 6061 can be cast - it is cast into an ingot shape prior to wrought processing.
Now, if you want to make a near-net shape part using a standard casting process like sand casting, gravity die casting, etc., then you will encounter problems.
As always, the more information you provide, the more helpful the replies will be.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
Goahead is right, 6061 standard is specific to wrought material. Casting alloys (and there are alloys that are functionally equivalent to 6061). Yes they are cast as an ingot but they are roll formed afterwards and that changes the metallurgical structure, this doesn't happen in cast parts so alloy additions have to be made to compensate for that lack of grain refinement. Cast grain structures are fundamentally different than wrought structures and it affects the performance of the part in different ways. When converting a part from a machined or welded process to casting, that needs to be kept in mind.