Solidification of the Glass-Forming Al86Ni2Co6Gd6 Melt under High Pressure

TL;DR

This study explores how high pressure influences the structure, crystallization, and hardness of the Al86Ni2Co6Gd6 alloy, revealing pressure-induced phase formation and increased glass-forming ability.

Contribution

It demonstrates the impact of high pressure on alloy solidification, microstructure, and hardness, combining experimental analysis with ab initio simulations.

Findings

High pressure induces new crystalline phases in the alloy.

Samples formed under high pressure have nearly double the microhardness.

High pressure increases icosahedral clusters, enhancing glass-forming ability.

Abstract

High pressures allow the synthesis of new metastable compounds that remain intact for a sufficiently long time at normal conditions. Until now, it has not been fully understood how pressure, glass-forming ability and solidification of liquids are interconnected. We have investigated the structure of the glass-forming eutectic alloy Al86Ni2Co6Gd6 obtained by rapid cooling from the melt having a temperature of 1800 K under a pressure of 10 GPa. X-ray diffraction analysis and electron microscopy show that the samples are homogeneous and dense. The structure is finely dispersed. New stable crystalline phases with cubic (cP4/2) and tetragonal (tI26/1) structures are formed in the alloy. The studies have shown that the average microhardness of the samples obtained at 10 GPa is almost 2 times higher than that of the original sample at atmospheric pressure and is about 1700 MPa. To understand the results, we used ab initio molecular dynamics and studied how the melt changes with pressure. It is shown that at a temperature of 1800 K, high pressure increases the concentration of icosahedral clusters in the melt so that at 10 GPa atoms inside the icosahedra form a percolation cluster, while at atmospheric pressure they do not. Thus, the glass-forming ability of a melt increases at high pressure strongly influencing solidification processes.