By discharging a capacitor through a coil you can electromagnetically form metal nearby the coil; this is most famous in the form of “quarter shrinkers”, but those exert so much force that they destroy the coil. But electromagnetic forming can be applied in less violent ways that permit the coil to be used repeatedly. I have seen spectacular demonstrations by a scholar at OSU using pulses of only 2kJ and 4kJ.
Unlike with physical impacts, there’s no inherent limitation to how fast this can happen; a hammer moving at 100 m/s can’t push material ahead of it faster than 100 m/s (though bouncing off it can accelerate hard material to faster than that). But electromagnetic forming is limited only by the inductance and voltage of your coil; submicrosecond rise times should be feasible, although I think there is a tradeoff in which larger numbers of turns produce slower rise times (at a given voltage) but higher peak forces. This might make it possible to do cold welding, particularly of thin foils.
One use I was thinking about just now is fastening hollow rivets, similar to pop rivets, through holes. By inserting a coil into a metal tube and discharging a pulse through it, the tube can be plastically expanded, and its ends can be flared, forming a permanent connection. If the center of the coil is either a ferrite (ferromagnetic or ferrimagnetic) or some other kind of hard ceramic such as alumina or zirconia, it will tend to protect the coil from being shrunk in the process.
The same coil may be used to preheat the rivet through electromagnetic induction in order to soften it before the electroforming operation; induction heating is feasible for any metal, but is easier (can be done at lower frequencies) for ferromagnetic metals.
The same kinds of forming can be used to seal together pipes or structural tubing end-to-end, as mentioned by the OSU scholar.