Improvements to a Friction Stir Extrusion Machine

Abstract Friction stir extrusion is a variation of friction stir processing, of which the most well-known is friction stir welding where a non-cutting rotating probe comes into contact with two metal sheets or plates. For friction stir welding, the friction between a rotating probe and the two metal sheets generates heat so that the temperature of the sheets increases above the recrystallization temperature and the material of the two metal sheets are stirred and upon cooling, results in a joined sheet. Within the stir zone, the grain structure is an ultrafine. For friction stir extrusion, the rotating probe is plunged into a work piece and the resulting heat raises the work piece to above the recrystallization temperature as either a solid or hollow cylindrical rod is formed. The previous version of the custom-built machine friction stir machine had significant vibration present during tests, difficulty in mounting the tooling on to the machine, errors in the workpiece temperature readings, alignment of the probe and work piece, and other manufacturing defects that made the machine difficult to be used for research and testing. This paper documents improvements to the friction stir machine and provides preliminary test data prior to a full-scale investigation of friction stir extrusion processes. Data in the paper includes observations, pictures, and force and temperature results.