Cold or contact welding is a solid-state welding process in which joining takes place without fusion / heating at the interface of the two parts to be welded. Unlike in the fusion-welding processes, no liquid or molten phase is present in the joint.
Cold welding was first recognized as a general materials phenomenon in the 1940s. It was then discovered that two clean, flat surfaces of similar metal would strongly adhere if brought into contact under vacuum. Newly discovered micro and nano-scale cold welding has already shown great potential in latest nanofabrication process.