Surface quality of aluminium extrusion products

Aluminium extrusion is a forming process used to produce profiles, and accounts for almost a half of aluminium production. By forcing a heated billet through a die opening that resembles the required profile shape, a large variety of profiles can be made efficiently. In this thesis, an important aspect of extrusion is addressed: surface quality of the extruded products. Surface hot cracking and incipient melting are not part of this research though, as they occur outside the appropriate process window. Surface defects occurring inside the process window, namely, the formation of surface pickups, have been studied.