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

Abstract

The present work reports grain refinement studies on AI-O.2%Zr and Al-2%Zr alloys using an Al-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 Al-5Ti-1B. This poisoning effect was milder at higher concentrations of Zr and in the presence of impurities in Al. The influence of Zr and impurities on the grain refining efficiency of Al-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 Al-Zr alloys.