4. Other solid-state joining processes based in part on diffusion

Other solid-state joining processes also rely on diffusion to form atomic continuity between two materials, but they mainly involve high plastic deformation (with a high strain rate) at the joint. Nor do they maintain the two parts of the joint under isothermal conditions, like the two processes just presented.

Friction welding and ultrasonic welding use friction to heat the material at the joint (with continuous or alternating deformation, respectively). Thermal control in friction welding is achieved by the formation of "beads" of highly deformed material, and assembly is theoretically achieved without fusion. However, the author was able to conclude experimentally that the ejection of liquid material into the parting line of nickel-based superalloys is very limited. Ultrasonic Al/Al welding is widely used in the electronic components industry.

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