Abstract: Memory metal plugs adapted to seal tubes are formed with a central post and laterally extended disks or rings. The plugs are formed from memory metal that is machined and heat treated to establish favorable temperature profile for the memory metal. The plugs are deformed in an apparatus that holds the plugs and cools the plugs to transform them into the martensitic state. A ram is used to force the cooled plugs through a die to decrease their diameter. These plugs can then be inserted into a tube and heated, causing them to return to their original state and thereby plug the tube.