Method for Inhibiting Grain Growth of Al-Zn-Mg Based Aluminiun Alloyed Billet for Thixo-Extrusion

摘要

The present invention is to suppress the grain growth of Al-Zn-Mg series aluminum alloy for semi-solid extrusion billet provides a method. The present invention is characterized in that it comprises a temperature rising step including a three-stage process with respect to the more elevated temperature Sc addition step and the casting of billets from the molten metal by the addition of 0.05 to 0.15% of Sc in the molten metal. In this case, Sc may be added to the Al-2 wt% Sc Sc master alloy in molten state, may have a holding time of 5 to 10 minutes after each temperature raising process is ended. The grain growth of the aluminum alloy billet produced by the method of the present invention is not more than 10% relative to the initial grain area. ; in the half melt-extrusion method without adding cost and additional equipment according to this invention is economical because the grain growth can be produced a small Al-Zn-Mg series aluminum alloy billet, and out of the crystal grains can be finely and provide a uniform billet.