한국주조공학회

Optimum conditions for production of semi-solid Al-Zn-Mg alloy billets was carried out by the Taguchi design method. And, Al-Zn-Mg alloy billets contained Sc (free, 0.1 and 0.3 mass %) were fabricated at optimum conditions. Evolution of microstructure in semi-solid state was investigated through various liquid fractions, holding times and holding temperatures. The Al-Zn-Mg alloy billets reheated at 615oC during 30min are grain growth and it was fractured due to increasing liquid fraction before quenching. And, during reheating up to 600oC, grain growth of Al-Zn-Mg alloy billets contained Sc (0.1 and 0.3 mass %) was not occurred in comparison with those of Al- Zn-Mg alloy without Sc. It was thought that Al3Sc phases have a pinning effect in grain boundary and Sc content of 0.1 mass% is able to inhibit grain growth effectively through reheating process.

Al-Mg-Zn alloy, Scandium, Reheating, Thixo-extrusion, Semi-solid.