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

Abstract

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.