The effects of Sc and Zr alloying additions on grain refinement and recrystallization resistance of 5xxx Al-Mg alloys have been assesed with the aid of computational alloy thermodynamics. The grain refinement potential has been assessed by Scheil-Gulliver simulations of solidification paths while recrystallization resistance (Zener drag) has been assessed by calculation of the precipitation driving forces of the Al₃Sc and Al₃Zr intermetallics. Microstructural performance indices have been derived and used to rank several alloy composition variants and finally select the variant with the best combination of grain refinement and recrystallization resistance. The method has been applied to the determine the optimum additions of Sc and Zr in a 5083 alloy (Al-4.5Mg-0.55Mn-0.1Si -0.1Cr mass %). Amongst the four alloy variants studied, the 0.4Sc+0.15Zr presented the highest potential for grain refinement while the 0.4Sc+0.08Zr variant presented the highest potential for recrystallization resistance. However the alloy variant 0.4Sc+0.15Zr presented the best combination of both grain refinement and recrystalization resistance.

Contributors: G.N. Haidemenopoulos, A.I. Katsamas and H. Kamoutsi