METHOD FOR INHIBITING GRAIN GROWTH OF AL-ZN-MG BASED ALUMINIUN ALLOYED BILLET FOR THIXO-EXTRUSION

摘要

PURPOSE: A method for inhibiting grain growth of Al-Zn-Mg based aluminium alloy billet for thixo-extrusion is provided to form billet with fine inner and outer grains without separate facility or additional cost. CONSTITUTION: A method for inhibiting grain growth of Al-Zn-Mg based aluminium alloy billet for thixo-extrusion comprises a step of adding Sc 0.05~0.15% to molten metal, and a step of performing three or more stages of temperature increasing processes on billet made out of the molten metal, wherein the billet is maintained for 5~10 minutes after each temperature increase process.