Strain and texture in friction extrusion of aluminum wire

Friction extrusion is a solid-state process that can produce high quality, fully consolidated wire or rod directly from metal chips, powder or billet. However, little is understood regarding the variation in material flow or extrusion strain with changes in processing parameters. Extrusion strain level may be of great import in determining whether or not the charge is fully consolidated. In order to explore the material deformation behavior during this process, flow visualization experiments were conducted using AA6061 billets with AA2195 as a marker insert. Variations in material flow during a single extrusion were documented and correlated with changes in grain size, which has previously been correlated with extrusion temperature. Marker shape was used to make an approximation of imposed strain during the extrusion as a function of relative extrusion temperature. Also, tests using various extrusion forces and die rotation speeds were conducted. The influence of extrusion parameters on deformation evolution was elucidated and discussed. Grain orientation analysis conducted using electron backscatter diffraction showed a fully recrystallized microstructure with weak texture indicating that recrystallization was likely a static process occurring after passage of the wire through the die. Key findings include: (1) longitudinal strain is solely a function of overall reduction (2) in plane shear strain decreases with increasing extrusion temperature, and (3) with increasing extrusion temperature, friction extrusion becomes similar to normal extrusion.