Grain refinement of Al–Si–Mg cast alloys by Al3Ti3B master alloy

Abstract

The requirements of lightweighting structures drive the improvement of mechanical properties of cast Al–Si–Mg alloys. Grain refinement is a way to improve mechanical properties. Al5Ti1B master alloy with TiB2 and extra Ti is widely accepted in industry for the grain refinement of aluminium alloys, especially wrought aluminium alloys, but it is hard to meet the expectations of cast Al–Si–Mg alloys due to the poisoning effect by Si. Al3Ti3B master alloy with TiB2 and extra B was prepared for the grain refinement of cast Al–Si–Mg alloys. The microstructure of cast Al9Si0.45Mg alloys under the refinement of Al3Ti3B and Al5Ti1B master alloys were investigated. The grain size of the primary α-Al phase in the Al9Si0.45Mg alloy refined by Al5Ti1B is 511 ± 104 μm, and that is decreased significantly by 55% to 231 ± 64 μm in the Al3Ti3B refined alloy. The mechanisms of grain refinement were discussed.