The biggest issue to worried about when using non steel or titanium materials to build a compression fit device i.e. barrel nut is thread lose due to over tourqe also know as qualing.
As far as aluminum goes in a barrel nut that is the only worrie you should have over a steel or titanium barrel nut is over tourqing it and ripping out the threads are completely locking the two peices together due to not using a proper lubricate when thighting the two interfaces together.
Hope this helps.
Edit to add make sure the nut is made of 7075 t6 aluminum.
As far as aluminum goes in a barrel nut that is the only worrie you should have over a steel or titanium barrel nut is over tourqing it and ripping out the threads are completely locking the two peices together due to not using a proper lubricate when thighting the two interfaces together.
Hope this helps.
Edit to add make sure the nut is made of 7075 t6 aluminum.