Crystallographic study of Al3Zr and Al3Nb as grain refiners for Al alloys

Abstract

The potency of Al₃Zr and Al₃Nb as grain refiners for Al alloys was investigated from a crystallographic point of view using the edge-to-edge matching (E2EM) model. The results show that both Al₃Zr and Al₃Nb have small values of interatomic spacing misfit and interplanar spacing mismatch with respect to Al. Furthermore, energetically favourable orientation relationships predicted by the model exist between Al and each of these two intermetallic phases. In the light of the edge-to-edge matching model predictions, it is suggested that both Al₃Zr and Al₃Nb are potent heterogeneous nucleation refiners for Al grains from the crystallographic point of view. The present crystallographic analysis provides a more reasonable explanation for the significant grain refinement obtained in the peritectic Al-Zr and Al-Nb alloys and also provides fresh insight into the understanding of the grain refinement mechanism of Al alloys.