Nucleation of Al2Ca particles on Al2Nd phase in an Mg-Al-Ca-Nd alloy

The distribution and structure of second phases in an Mg-12Al-6.5Ca-1Nd alloy prepared by spray deposition technique were studied using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) combination of energy dispersion spectrum (EDS) mapping. Results show that several Al2Ca particles nucleated on the Al2Nd phase, revealing the initial liquid appearance of Al2Nd which finally led to the formation of heterogeneous nucleation sites. Low interfacial energy between the phases caused by closed lattice parameters is responsible for the heterogeneous nucleation. The crystallization sequence can be explained satisfactorily by the phase stability obtained from first-principles calculations. (C) 2019 Elsevier B.V. All rights reserved.