Friction-Stir Welding and Processing

Friction-stir welding (FSW) creates solid-state flow in butted metals and alloys which are mixed in the resulting weld zone. A rotating tool stirs one material into the other by the creation of DRX grains which result by extreme deformation, creating adiabatic heating at the tool/material interface. The process bonds or joins same or dissimilar metals and alloys and is not limited by thermodynamic considerations in conventional fusion welds. Unlike fusion welding, the tool is not purposely consumed. Friction-stir processing (FSP) uses a rotating tool as in FSW with some dimensional restrictions to allow controlled surface depths to be altered, microstructural alteration. Continuous tool traverse and overlapping stir regimes produce a modified or remodeled surface region or thickness where second phase as well as other microstructures can be homogeneously distributed. Bubbles or voids can be eliminated in cast materials. Properties and performance such as superplasticity can be affected by creating DRX nanograins.