Role of zirconium and impurities in grain refinement of aluminium lNith AI-Ti-B

Abstract

The present work reports grain refinement studies on AI-O.2%Zr and AI-2%Zr alloys using an AI-5Ti-1B master alloy as the grain refiner. The influence of impurities (Fe and Si) present in Al on the poisoning tendency (adverse effect) of Zr on grain refinement has also been studied. Zirconium was found to be a potential grain refiner of Al at high concentrations (2%). However, Zr has shown poisoning effects on the good grain refining capability of AI-5Ti-1B. This poisoning effect was milder at higher concentrations of Zr and in the presence of impurities in AI. The influence of Zr and impurities on the grain refining efficiency of AI-5Ti-1B is discussed in the light of macroscopic examination, grain size analysis, SEM and energy dispersive X-ray microanalysis, electron probe microanalysis, and TEM studies on AI-Zr alloys.