Grain refinement effect of Al-Sc-B master alloy for Zr/Sc containing Al alloys

Traditional Al-Ti-B/C grain refiners subject to "poisoning effect" when Zr/Sc elements are contained in Al alloys during inoculation. To overcome the difficulty, an Al-2Sc-0.5B master alloy was prepared in this work. It was found that ScB2 and ScAl3 were the main secondary phases in the alloy. Introducing 0.01 % Sc using the Al-2Sc-0.5B to commercial purity Al-0.13Zr alloy, its alpha-Al grain size could be refined from 1179 mu m to 646 mu m. However, adding 0.01 %Sc using Al-2Sc master alloy which just contained secondary phase of ScAl3 showed nearly no grain refinement effect. It indicated that ScB2 played important role in the grain refinement. According to crystallographic analysis, (0001)ScB2 and (111)Al had the same atomic arrangement, and crystal mismatch between them was similar to 7.71 % at 660 degrees C. Thus, ScB2 was proposed a potential nucleation substrate for alpha-Al.