Novel thixoextrusion process for Al wrought alloys

The aim of this study is to develop novel thixoextrusion process for hard-to-form Al wrought alloys. Thixoextrusion for 7003 Al alloy of Al–Zn–Mg system and 7075 Al alloy of Al–Zn–Mg–Cu system were investigated as functions of isothermal holding temperature and time in the partially remelted semisolid state. The interesting point of the results was that the thixotropic structures of 7003 and 7075 Al alloys could be obtained without additional pretreatment only through simple partial remelting. More than that, the thixoextrusion pressure of 7075 Al alloy was lower than the thixoextrusion pressure of 7003 Al alloy at the same liquid fraction of 10%, despite the big difference of extrudability index between 7075 and 7003 Al alloys. The microstructures of thixoextruded specimens did not show any dendrites or rosette-like structures.