Effect of the Al–Zr–Y master alloy composition on the modifying effect in the Al–4% Cu alloy

Resumo

The results of modifying the Al–4% Cu alloy with test Al–1.04% Zr–0.70% Y and Al–1.23% Zr–0.39% Y master alloys are reported; the Zr-to-Y atomic-percentage ratio in the alloys is 1.41 and 3.08, respectively. The effect of small amounts of Zr and Y (from 0.1 to 0.3%) added in the form of test ternary master alloys of different compositions and binary Al–Zr and Al–Y master alloys on the grain refinement in the Al–4% Cu alloy has been studied. The structure of the initial alloy is characterized by pronounced directional solidification of the α phase. As the Zr + Y content increases, the columnar-crystal zone decreases and the equiaxed-crystal zone increases; at a (Zr + Y) content of 0.326%, only equiaxed crystals ~200 μm in size are present in an ingot. When Zr and Y are added with binary master alloys, the macrostructure of the modified Al–4% Cu alloys indicates that columnar crystals grow until their contact at the center of the ingot, and their growth is independent of the amount of added Zr and Y.