Changes in processing characteristics and microstructural evolution during friction extrusion of aluminum

This study focuses on characterizing the microstructural evolution of the aluminum alloy 7075 in the friction extrusion process under different extrusion forces and die angles. Depending on these conditions, two fundamentally different extrusion types are found, showing significant differences in the process characteristics and microstructural evolution. One of the two extrusion types is associated with high extrusion force and low die angle, leading to fully recrystallized wires with average grain size around 1.2 mu m. The microstructural analysis indicates that the microstructure present in the wires is generated in the charge material by the combination of tool geometry, load induced material flow and friction conditions in the initial stages of the friction extrusion process. The identified processing conditions and influencing factors introduce an alternative route for friction extrusion at low extrusion ratios, capable of producing completely refined wires.