Friction stir consolidation of aluminum machining chips

Friction stir consolidation (FSC) is a solidphase manufacturing process that consolidates metal powder, chips, or scraps into solid blocks via severe plastic deformation and solid state welding. It has the potential to be a more economical and green process to recycle metal waste. In this study, solid discs were made from AA6061 aluminum alloy machining chips by FSC. The progression of the process was revealed by analyzing the motion of the tool, consolidating force, power history, and macro/microstructure of discs produced from a series of partial consolidation experiments. A bowl-shaped recrystallized zone in the vertical cross-sections of the disc products was observed and considered as the fully consolidated region. Design of experiments was conducted to quantify the effect of die rotational speed, compressive force, and processing time on the volume of fully consolidated material. A numerical model was used to predict the evolution of the main field variables such as density and temperature.