ROLE OF ZIRCONIUM AND IMPURITIES IN GRAIN-REFINEMENT OF ALUMINUM WITHAL-TI-B

The present work reports grain refinement studies on Al-0.2%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 ten dency (adverse effect) of Zr on grain refinement has also been studied . Zirconium was found to be a potential grain refiner of Al at high co ncentrations (2%). However; Zr has shown poisoning effects on the good grain refining capability of Al-5Ti-1B. This poisoning effect was mil der at higher concentrations of Zr and in the presence of impurities i n Al. The influence of Zr and impurities on the grain refining efficie ncy of Al-5Ti-1B is discussed in the light of macroscopic examination, grain size analysis, SEM and energy dispersive X-ray microanalysis, e lectron probe microanalysis, and TEM studies on Al-Zr alloys.