Effect of Fe-Rich Particles on the Formation of Die Streaks on Anodized Aluminum Extrusions

Fe-rich intermetallic particles are one of the important constituents in the microstructure of 6xxx series aluminum extrusions. The size, amount, and distribution of these particles can be different in different locations of the extrudate due to inhomogeneous deformation during the extrusion process. Furthermore, these intermetallic particles change the dissolution kinetics of grain interiors and grain boundaries during etching, influencing the formation and severity of grain boundary grooves. An inhomogeneous distribution of Fe-rich particles results in a nonuniform distribution of grain boundary grooves and occurrence of die streaks.