What is the metal use in rail guns?

Question

The type of metal when two dissimilar metals are in contact when a electric charge is applied the one metal propels itself.

Answer 1

A railgun consists of two parallel metal rails (hence the name) connected to an electrical power supply. When a conductive projectile is inserted between the rails (from the end connected to the power supply), it completes the circuit. Electrical current runs from the positive terminal of the power supply up the positive rail, across the projectile, and down the negative rail, back to the power supply.

This flow of current makes the railgun act like an electromagnet, creating a powerful magnetic field in the region of the rails up to the position of the projectile. In accordance with the right-hand rule, the created magnetic field circulates around each conductor. Since the current flows in opposite direction along each rail, the net magnetic field between the rails (B) is directed vertically. In combination with the current (I) flowing across the projectile, this produces a Lorentz force which accelerates the projectile along the rails. There are also forces acting on the rails attempting to push them apart, but since the rails are firmly mounted they cannot move. The projectile slides up the rails away from the end with the power supply.
The need for strong conductive materials with which to build the rails and projectiles; the rails need to survive the violence of an accelerating projectile, and heating due to the large currents and friction involved. The force exerted on the rails consists of a recoil force - equal and opposite to the force propelling the projectile, but along the length of the rails (which is their strongest axis) - and a sideways force caused by the rails being pushed by the magnetic field, just as the projectile is. The rails need to survive this without bending, and must be very securely mounted.

Answer 2

Way to plagiarize Wikipedia, sendfromme...

Any type of conductive material could theorectically be used to contruct a railgun. Since all metals are electrically conductive, any metal would work.

The problem with railguns is the tremendous amount of force and heat generated when they fire. In order to have a usable weapon, it would be neccesary to build it out of very strong, heat-resistant metal that still has high conductivity. The guys that built one in the link below used silver-plated copper.