Efficiency of binary and ternary alloys from Al-Ti-B system in grain refining aluminium foundry alloys

摘要

Several binary and ternary alloys from the Al-Ti-B system were tested for their capacities to grain refine aluminium foundry alloys. The growth restriction factor estimations evidence that the Al-3Ti alloy contributes to the grain refinement of AlSi7Mg0.3 alloy via only growth restriction, providing a twofold reduction in grain size. There is a marked improvement in the grain refining efficiency when Al-Ti-B ternary alloys are employed. While the efficiency increases with increasing B concentration, the mild improvement over a wide range of grain refiner compositions implies that the AlSi7Mg0.3 alloy is not very sensitive to the composition of the ternary Al-Ti-B grain refiners. Al-3B alloy provides the smallest grains at an addition rate of 200 ppm B, producing an average grain size of 298±36 μm in the commercial AlSi7Mg0.3 alloy. The grain refinement efficiency is doubled when the Al-3B grain refiner was added to the Ti free counterpart with average grain size of 145±10 μm.