Formation of long-period order structure in Mg-based amorphous matrix composite

In order to improve the plasticity of Mg-based amorphous alloy, the crystal phase with long-period order (LPO) structure was introduced into the Mg-based amorphous matrix, and the influence of Y/Zn ratio on the formation of LPO structure was investigated. Mg₇₇Ni₁₂Zn_9-xY_2+x(x=0, 2, 4, 6) amorphous matrix composites were fabricated using copper mold casting method. The microstructure, phase constituent and composition of the composites were analyzed by scanning electronic microscope (SEM), high-resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDX). The results show that the minimum Y/Zn ratio to form the LPO structure with 14H type characteristic is 0.57. The Y/Zn ratio to form the LPO phase distributed uniformly in the amorphous matrix is about 1.2, where the proportion of Y and Zn atoms in the LPO structure is slightly above 1. The existance of Ni element results in a change of the LPO structure from 6H to 14H type characteristic. In addition, the formation mechanism of LPO structure in amorphous alloys with critical composition was given based on both nucleation and growth processes of various phases during solidification.