Al Extrusion Vibration Damping

Just curious if anyone has any thoughts on how to increase the vibration damping
characteristics of aluminum framing products.

I had thought about filling the voids in the extrusion with sand and capping the ends.

Another idea was to fill the void with small lead pellets such as lead shot. A friend had the
idea of heating the extrusion just enough to melt the lead together, but I don't know if the
melting point of lead would cause a loss of heat treatment to the framing.

Any ideas or thoughts? I really like the flexibility of this product in machine design, but I fear
when I finish building my mill I will have horrible chatter.