Before that they could build a habitat the size of a jumbo jet suspended high in the atmosphere by hydrogen balloons. I can't think of away to make it safe, though.

Hello freedomforall,
This is quite fascinating. In my business I am familiar with many foundries that have to go to great lengths to insure their material is cast without any voids within. If they have them they often fail x-ray inspection standards and are considered as structural flaws.
Respectfully,
O.A.

Off planet self reliant 'liberty' habitat a mile 'tall' ;^)

I hope to see a building a mile tall in my lifetime.

An alloy of magnesium.
It may be highly inflammable.

Amazing! This could be a break through material. Does any one know how it welds?
Does it lend itself to 3D printing?