Take a Look at Friction Welding of Titanium in Slow Motion
Friction welding is a process of joining 2 metals through the friction produced by rubbing them together. The process can often be used to join dissimilar metals, it is typically seen in automotive manufacturing applications. Technically speaking, the process is not actually welding, but rather a forging technique because no melting of the metal is actually occurring. You can see the process in great detail in the slow motion video above.