Beryllium-enhanced grain refinement of aluminium–titanium alloys

Abstract

The addition of small amounts of Be markedly enhances the grain refinement of Al by Ti. It is shown that Be is incorporated into the peritectic compound TiAl₃, and that the ternary compound Ti(Al, Be)₃ has a higher nucleation entropy and a corresponding significantly higher nucleation rate, which is in agreement with the observed enhancement in grain refinement. A decrease in grain refinement when the Be content exceeds the eutectic limit for the Al–Be system (∼0·87%) is related to the formation of the compound Be₁₇Ti₂, which decreases the amount of the peritectic compound formed, and hence decreases the nucleation rate and grain refinement.