The nucleation crystallography and wettability of Mg grains on active Al2Y inoculants in an Mg–10wt% Y Alloy

Abstract

Heterogeneous nucleation of metals from liquid is a key concept in physical metallurgy and is of great technological significance in grain refining of cast metals and alloys. However, it is a long-standing challenge to trap active nucleants for characterization due to their scarcity in grains. With the aid of Focus-Ion-Beam (FIB) milling technique, the nucleation crystallography is, for the first time, fully characterized between Mg nuclei and active Al2Y inoculants in an Mg–10 wt% Y alloy using transmission electron microscopy (TEM). An epitaxial orientation relationship, i.e. [112¯0]Mg∥[1¯2¯1]Al2Y,(0002)Mg∥(2¯22)Al2Y has been invariably identified. Based on the quantified interfacial energy between the Al2Y and Mg, it is found that Mg can be fully wetted on Al2Y inoculants. In addition, the wettability of Mg on a number of other isomorphic compounds to the Al2Y inoculants is also discussed in term of their interatomic spacing misfit along matching directions with Mg.