Grain Structure Evolution Ahead of the Die During Friction Extrusion of AA2024

Friction extrusion (FE) is a thermo-mechanical process using a rotating die or feedstock to produce fully consolidated extrudates in different shapes, e.g. wires, rods and tubes. FE utilizes a non-consumable die to plastically deform material and generate heat by friction due to the relative rotation between the die and feedstock, i.e. FE represents a more energy-efficient process compared to classical extrusion techniques. In this study, the FE process is applied to extrude the Al-Cu alloy AA2024 using a 90 degree scroll-featured die. The grain structure evolution induced by thermo-mechanical processing is analyzed, in particular using the electron backscatter diffraction technique. Introduction of severe plastic deformation and high-temperature exposure induced by the die movement in radial and longitudinal directions relative to the materials enable grain refinement induced by dynamic recrystallization. The grain structure formation prior to deformation through the die orifice plays an essential role to obtain fully recrystallized homogeneous wires.